ES2923973B2 - Procedures for improving the synthesized material C12A7:e- "electride", cathode architectures for electron emission that take advantage of the characteristics of the material C12A7:e "electride" and use of special substrates and procedures for the deposition of the material C12A7:e- " electride" on said substrates - Google Patents

Description

DESCRIPTION

Procedures for improving the synthesized material C12A7:e- “electride”, cathode architectures for electron emission that take advantage of the characteristics of the material C12A7:e “electride” and use of special substrates and procedures for the deposition of the material C12A7:e- “ electride” on said substrates

TECHNIQUE SECTOR

The present invention refers to various architectures and configurations used to design cathodes based on the use of the C12A7:e-(“electride”) material as an electron-emitting electrode when an interaction of the electrode with ions occurs in both liquid and gaseous media ( plasmas) or as an electrode that gives up electrons to other materials when the contact is not strictly ohmic but rather as a metal-semiconductor junction or by direct electron jump from the electrode to ions in a fluid medium. That is, the field of application includes devices where the cathode interacts with (positive) ions, giving up electrons.

Likewise, it refers to the use of charge coupling techniques between the cathode and an auxiliary physical electrode, (the "keeper") or one that is formed by the ions themselves that are described and claimed in the previous application P202130778 dated December 10. August 2021 of which the applicant himself is the owner.

The fields of application will be those likely to use said electrode-metal or electrode-ions or electrode-vacuum interaction as the actual electron emitter, such as the aerospace field: electron-emitting cathodes, both in vacuum and with plasma, for neutralizers ( emission of electrons to neutralize the ion beam responsible for the impulse) and to cause the ionization of the propellant gas of the thrusters. Systems, in general, that involve the interaction of the electrode, made with the material C12A7:e-, with ions in either a gaseous state (plasma) or a liquid state or as a combination of both liquid-gas, as is the case of the electrolysis of water. for hydrogen generation, the fuel cell for the generation of electricity from hydrogen, both low temperature (PEM type) and high temperature (SOEC and SOFC). The invention focuses on the maximum use of the properties of the C12A7:e- “electride” material as a cathode and its stable operation under different conditions, through specific pulsed polarization techniques, arrangement of auxiliary electrodes, selection of the appropriate materials, shapes deposition of the material on the substrates or supports and modes of operation to achieve stable and controlled operation.

BACKGROUND OF THE INVENTION

It is important to highlight application number 202130778 dated 08/18/2021 in which the origin of the main stability problems of the C12A7:eelectride material is identified and the mechanisms to avoid them are established and explained. Among them, the most relevant mechanism is the use of polarization or pulsed excitation, always negative, consisting of a square signal with different cyclic relationships ("duty cycle") and different frequencies depending on the application. The signal will always be negative with respect to ground or zero potential reference. In the present invention, use will be made of that original invention, extending it to cases where temperature is the excitation energy of the cathode, that is, the heater receives a pulsed signal, so the thermal radiation will always be pulsed.

On the other hand, a procedure is introduced to improve the characteristics of the material once synthesized, which we will call "Forced Reduction" described in the present invention, consisting of combining traditional procedures based on temperature and the use of reducing elements (such as Ti, C, Gd, Sm, Ca, V and gases such as hydrogen) adding electrical signals (both continuous and pulsed) always negative with respect to the zero reference potential (mass) that force the reduction (transfer of negative ions and/or electrons). No precedents have been detected for forced reduction applied to the C12A7:e- “electride” material for the improvement of the material.

No cathode designs have been found for use as an electron emitter in the aerospace industry (neutralizers and propellants) with the special characteristics proposed for the use of the C12A7:e- “electride” material.

It is a verified fact, until the date of presentation of the present invention, that no The use of the material C12A7:e- “electride” has been proposed as a catalyst in the cathodes of electrolyzers and low-temperature PEM fuel cells, nor high-temperature SOEC and SOFC, respectively. It is logical that this is so given that without the techniques detailed in the present invention (or other equivalents that are unknown), both at the level of improvement after synthesis (forced reduction), deposition techniques on electrolyzer electrodes and fuel cells and post-deposition treatment techniques, it would be very difficult to ensure that the material, in addition to functioning, did not degrade immediately.

Part of the search carried out previously is reproduced, with negative results in the applications proposed in the present invention.

The analysis of the state of the art of inventions has been carried out on a total of more than 800 different patents. All those patents that mention the use of C12A7 material (297 results) or mayenite (257 results) have been compiled for analysis, resulting in some of them being very similar but with different identification.

In addition to these search criteria, the study has been extended to all those patents that mention the use of electride-type compounds in order to collect those inventions that could be related by referring to the use of this type of compounds in a generic way. This additional search resulted in 338 results.

Eliminating the results that appear duplicated in the different searches, we are left with a global result of a set of 848 different patents, spanning from June 1903 (US916575A) to December 2020 (CN112592085A)

The first 31 patents, prior to the discovery of Mayenite in 1964 in Mayen (Germany) have been analyzed for mentioning the use of “electride” type compounds in their invention. Some of them refer to components of valves and vacuum tubes or other types of apparatus and discharge devices (US1479778A, CA310089A, US2351305A, CA495721A, US2735037A), but in none of them have claims been found regarding the use of the mechanisms. and capacitive coupling techniques to promote thermionic emission, nor on the architectures and component elements of the cathode designs described in the claims. of the present invention.

Since its discovery in 1964, the mineral mayenite and its synthesized ceramic material C12A7 were massively used in the cement industry, but it was not until the early 2000s with the first research in Japan and especially with those of Professor Hideo Hosono's team when it was discovered. managed to transform the C12A7 ceramic into the “electride” compound C12A7:e- by replacing oxygen ions with electrons.

The appearance of the first patent relating to an “electride” compound derived from C12A7 ceramic took place in 2001 in Japan (JP2001321251A) and was later extended and published as EP1445237A1; EP1445237A4; EP1445237B1; JP2003128415A; JP3560580B2; US2005053546A1; US7235225B2; and finally published as WO03033406A1 dated 2003-04-24. It did not yet talk about the replacement of oxygen ions by electrons, but by OH- ions, although it was already indicated that it could have areas of application as a catalyst, as an antibacterial agent, as an ion-conducting material, or as an electrode for batteries. solid fuel. However, no specific apparatus or device is described, nor the mode of operation of this new compound for any of these applications.

Of the 248 patents resulting from the search that appear from 1964 to the aforementioned JP2001321251A dated 2001-10-18, there are 51 of them that are related to C12A7 or mayenite as a component of cements, a few are related to the material as a catalyst in general (DE10136478A1; EP1114675A2; EP1114676A2; ) and regenerable catalyst (EP1353748A2; EP1353748B1), and a few others as a component in the synthesis and manufacture of other types of materials and compounds other than “electride” (CN1202275C; CN1386144A; JP2001157837A; KR100333669B1; JP3699756B2) .

But the vast majority of these 248 patents refer to “electrides” in a general sense, either deposited or directly used as electrodes for different applications, of which only 41 are after 1993 (US6350994B1; CN1395106A; CN1268230C; CN1438840A; CN1327859A; US2001045565A1 ; US7339317B2; ITSV20000019A1; CN1316782A; US2001017679A1; JP2001144107A; WO0079546A1; WO0079546A1; CN1139115C; JPH11283441A; JPH11281476A; JPH11281476A;US5981866A; JPH11209033A; JP4011692B2; JPH11102661A; US5874039A; JPH1136099A; BG101700A; US6361822B1; US5994638A; JPH10178141A; BG103488A; EP0843410A2; US6103298A; CA2287006A1; JPH09134686A; JPH09167618A; JPH09180704A; JP3512295B2; JPH09122246A; JPH08207290A; US5618451A; JP2001315593A; JPH087658A; CA2183074A1). None of the patents referring to “electrides” published between 1964 and 2001 mention the use of specific cathode polarization mechanisms, much less any capacitive coupling mechanism for thermionic emission of electrons. Nor do they describe or claim designs that contain the elements that are included as claims in the present invention.

Starting from the first Japanese patent on the transformation of C12A7 ceramic into “electride” (JP2001321251A) dated 2001-10-18 and until the end of 2020, we find another 568 patents, of which, due to the fact that the C12A7 ceramic material has been used massively as a component of cements, it turns out that a high percentage of the patents refer to this use of the C12A7 material or mayenite, and not only in the oldest patents starting with the Lafarge Cements patent (US3705815A) in 1970, but also in very recent patents, especially by companies, research centers and universities in Asian countries such as Korea or China. Thus, for example, 20 of the 27 patents analyzed in 2020 refer to this type of cement compounds, while 5 include inventions related to the use of the “electride” material C12A7, or its compounds with Ru (Ruthenium) and other metals. , in applications as a catalyst. Only 2 patents from 2020 that mention the C12A7 material (CN111774276A and CN112201555A) describe inventions of thermionic emission devices.

On the other hand, of those 568 patents after JP2001321251A, there are also a large number of them that refer exclusively to the methods and processes of ceramic synthesis and its transformation into “electride” C12A7:e-, without going into a description. of devices or apparatus for any specific application (for example CN109208079A).

Focusing on the rest of the patents, once those referring to the manufacture of cements and their applications, and those referring to processes of synthesis and growth of thin layers of “electride” have been excluded, the rest can be grouped into three large sections: Devices and appliances for residential or industrial use such as discharge lamps, microwave ovens, photovoltaic solar cells, imaging and light emission devices, water and soil decontamination, lithium extraction, etc.

This first group includes a series of inventions related to devices and apparatus for different applications and uses:

In discharge lamps (JP2014006961A; JP2013104898A; JP2013045528A; TW201232599A; WO2011024821A1; WO2010074092A1; EP2302662A1; JPH11102661A) In microwave ovens (JP201 5216006A)

In photovoltaic cells (JP2020072085A; KR101920127B1; JP2010016104A)

For imaging and light emission (CN109880615A; US2015137103A1; JP2010016104A; EP1887605A2)

As a catalyst in various processes including decontamination of water, soil, and air (US2020282162A1; JP2020138902A; CN109485454A; CN109433199A; CN108855121A ; CN108892982A; CN109876866A)

For lithium extraction (CN109019643A)

None of the previous patents are comparable, neither in the architectures used nor in the forms of polarization of the “electride” nor in the applications themselves.

Devices and apparatus for electric propulsion.

The second group is a set of applications based on the high ionizing capacity of the “electride” and its use in electric propulsion systems both in propulsion and neutralization, and is where we can find some inventions and claims that use the expression pulsed for some type of operations (US2021100089A; US10269526B2).

Nor are there any claims in these patents that conflict with the claims of the present patent. They make no reference to the dielectric layer or to the need to apply charge coupling techniques to perform thermionic extraction of electrons through that thin non-conductive layer. They also do not indicate the polarization mechanism of the cathode, its amplitude, its sign with respect to the “keeper”, or its frequency. In the present invention, the so-called "keeper" is used as a charge coupling reference and not as an electrode with the same function performed by the vacuum tube grids for charge extraction or emission modulation. In fact, the current through said electrode in the present invention does not reach 2% (normally less than 1%) of the total emission current even if the anode is at zero volts (ground) or even at negative potential with respect to said grid or “keeper”, an aspect that is very difficult to achieve using any usual configuration as a grid or “keeper” as in the patents analyzed, where the “keeper” current becomes even greater than the anode current itself even when the anode positively polarized. This is one of the distinctive characteristics of the present invention given that, in all studies, articles, patents and references, the “keeper” current is comparable or higher than the anode current, also requiring a positive polarization of the anode. . In the present invention, the "keeper" current is less than 3% of the anode current, even reaching the order of 1%, and said anode can be polarized to zero or even negative with respect to ground. The current lost in the “keeper” is not useful for the final application since they are electrons that do not reach the anode, so the losses will be less than 3%. That is, practically all the current at the cathode, supplied by the external circuit, is converted into a beam of free electrons that reaches the anode.

Finally, it is important to highlight that the system based on charge coupling techniques between the "keeper" and the cathode included in the present invention has nothing to do with pulsed plasmas or certain pulsed regimes in neutralizers or ionic propellants. In all these cases, the pulsed regime refers to the plasma or emission itself, normally of low frequency. In the present invention, the pulsed regime is intrinsic to the cathode and does not have to be transferred to the plasma with the appropriate design, that is, the anode current can be practically DC (“quasi-DC”) with small ripples. Put another way, pulses may not translate to the plasma if the plasma decay time is longer than the idle time of the excitation signal (pulse time at zero volts).

Electrolyzers and fuel cells.

Although the replacement of noble metals (Pt, Pd, Ir, Ru) with more abundant and cheaper ones is the subject of intense international research, so far no device has been detected whose cathode is based on the use of the C12A7 material. :e-“electride” as a catalyst, nor its approach for replacing the group of noble metals. Both low temperature (PEM/AEM type) and high temperature (SOEC and SOFC respectively) electrolyzers and fuel cells are included, so the present invention aims to be the first clearly in this field. In particular, high temperature solid oxide electrolyzers (SOEC) and fuel cells (SOFC) are applications especially indicated for the use of the C12A7:e material given that it is a ceramic that operates up to 1000°C temperature, this being the for the first time that its use in such devices is being considered. Possibly, this fact has not occurred until now due to the degradation of the material under the usual conditions of use in electrolyzers and fuel cells. The introduced polarization techniques, negative pulses or negative continuous signal in addition to the material deposition techniques on the substrates that form the cathodes, and, above all, the improvement techniques after deposition based on “forced reduction”, are the differential factors that allow its use when it was not possible before.

EXPLANATION OF THE INVENTION

The present invention incorporates a series of novelties in different phases of the construction of the final devices, grouped into the following concepts:

1. - Procedures for improving the synthesized material C12A7:e- “electride”, applied to the final solid samples of different shapes (such as discs or hollow cylinders) or to the depositions made on substrates or supports depending on the type of application.

2. - Design of different cathode architectures for electron emission that take advantage of the characteristics of the C12A7:e “electride” material, the material improvement procedures (forced reduction) and the pulsed polarization procedures for the stabilization of the emission defined in the prior invention application P 202130778 dated August 10, 2021.

3.- Use of special substrates and procedures for the deposition of the C12A7:e- “electride” material on said substrates.

The use of specific substrates and supports to deposit the material instead of being used in a solid form has very significant advantages in terms of resistance to fractures and breaks under conditions of mechanical and thermal stress, overcoming the drawbacks of a ceramic material when used. in solid parts, especially in the aerospace field (neutralizers and propellants). It is also necessary when used as a cathode in electrolyzers and an anode in fuel cells since the cathodes (or anodes in fuel cells) are usually made precisely of carbongraphite fibers that contain the catalyst, make the electrical connection and allow the exchange of gases (known as GDL or Gas Diffusion Layer).

Regarding the improvement process of the C12A7:e- “electride” material, it is based on applying a “forced reduction” (substitution of oxygen ions for electrons) through negative polarization of the material to be reduced (substitution of oxygen ions for electrons). , in DC or pulsed regime, with respect to the ground or zero voltage reference. The improvement procedure can be carried out on the newly synthesized base material, the ground material, the material deposited on a substrate including said substrate or on a complete assembly that includes the material, the substrate and other constituent elements of the cathode.

In accordance with another of the characteristics of the invention, a reduction in temperature and/or process time has been planned with respect to the conventional reduction process (replacement of oxygen ions with electrons), which allows reduction and integration in the same process. not only the material but the substrate or a larger assembly that may be sensitive to temperature. The reduction and joint material-substrate process improves the conductivity of the material with the substrate when it is conductive, a key aspect for high performance. Forced reduction allows the reduction temperature to be lowered from the range of 950°C to 1250°C to the range of 650°C to 950°C and, above all, to reduce the process time.

As far as the substrates are concerned, the invention provides for the use of substrates on which the material is deposited with various techniques, especially the "spray" or nebulized mode (with or without high voltage assistance), as well as the procedure and formula to obtain the solution to be nebulized formed by the base material C12A7:e- “electride” and a non-aqueous solvent, including reducing additives as described in the present invention. The subsequent treatment of the material and substrate assembly includes forced reduction and the lowering of temperature and process time described above.

More specifically, carbon fiber type substrates will be used, activated or with graphite additives and carbon nanotubes to which the material is deposited according to the process described above.

Based on this structuring, the invention allows the development of different practical applications, among which the following should be highlighted:

• Construction of cathodes especially indicated for the aerospace sector, meeting the thermal and mechanical stress requirements to which they are subjected, avoiding the drawbacks of the ceramic nature of the material if it is used as a solid (disks, hollow cylinders, etc.). Ceramics fracture under conditions of thermal and mechanical stress, especially the material C12A7:e- “electride” due to its lack of homogeneity in electrical and thermal conductive properties, which causes internal stresses that end up fracturing the material. Since the cathode can be a carbon fiber substrate with the material deposited and subsequently treated (forced reduction), there is no possibility of fractures under conditions of extreme thermal or mechanical stress, due to the characteristics of the carbon fiber, but it is They maintain the emission properties of the original material by following the indicated procedures.

• Construction of cathodes for electrolyzers and anodes for fuel cells, both low temperature (type PEM or alkaline AEM) and high temperature (SOEC and SOFC respectively), where the GDL (Gas Diffusion Layer) that forms the cathode, normally at carbon base (carbon fiber, graphite paper and the like) contains C12A7:e- “electride” material deposited and treated as described above, acting as a catalyst in said devices.

• Construction of cathodes for water purification systems based on electrolysis.

Optionally, the invention provides for the possible substitution of noble metals (Pt, Pd, Ir, Ru) in cathodes used in electrolyzers and fuel cells, both low temperature (type PEM or alkaline AEM) and high temperature (SOEC and SOFC respectively). ) and in water purification systems based on electrolysis.

In accordance with another of the characteristics of the invention, it has been possible to verify the suitability of using a pulsed signal instead of direct current (DC), always with negative polarity, to avoid instabilities and achieve stable operation without material degradation. As well as the convenience of using an auxiliary electrode ("keeper") to facilitate charge coupling, the possibility of designing different cathodes for the emission of electrons suitable for the aerospace environment is claimed, using both solid material and deposited and treated in carbon fiber, which allows the thermal and mechanical stress requirements to be met, adding one more degree of freedom to the design itself.

In the case of application in space thrusters and neutralizers, the invention also provides for the use of an ionization chamber with an inlet and outlet section much smaller than the section of the chamber itself to produce an overpressure due to the Venturi effect. This overpressure allows the operation of the plasma with low gas feed rates and even lowers the cathode potential necessary to maintain the plasma. The walls of the chamber must be electrically insulating or covered with insulating material to prevent the neutralization (and therefore loss) of electrons and ions.

From these two characteristics, it is possible to develop the following types of cathodes:

• cathode with flat emitter and magnetic field for plasma operation without heater in side gas inlet variant.

• Cathode with flat emitter and magnetic field for plasma operation without heater in lower-central gas inlet variant.

• cathode with cylindrical emitter and magnetic field for plasma operation without heater in lower-central gas inlet variant and with auxiliary electrode lateral “keeper”.

• Cathode with cylindrical emitter and magnetic field for plasma operation without heater in variant with lateral gas inlet and with lateral “keeper” auxiliary electrode.

• Cylindrical emitter cathode without magnetic field for plasma operation in lateral gas inlet variant and with lateral “keeper” auxiliary electrode.

• Cathode with hollow cylindrical emitter without magnetic field for plasma operation in central gas inlet variant and with upper “keeper” auxiliary electrode.

• Cathode with hollow cylindrical emitter without magnetic field for plasma operation in central gas inlet variant and with lateral “keeper” auxiliary electrode.

• Cathode with hollow cylindrical emitter without magnetic field for plasma operation in gas inlet variant through lower holes in the emitter holding base and with lateral “keeper” auxiliary electrode.

• Cathode with hollow cylindrical emitter without magnetic field for plasma operation in central gas inlet variant and with double auxiliary “keeper” electrode (central and lateral).

• Hollow cylindrical emitter cathode without magnetic field for vacuum operation and with double auxiliary “keeper” electrode (central and lateral).

• cathode based on depositing the material C12A7:e- “electride” on a filament of W, Ta, Mo, using pulsed signals both to heat the filament and to establish its potential with respect to the mass reference (zero potential) which will always be negative. Incorporation of a polarized grid as part of the cathode to control the intensity of the emitted electron beam.

BRIEF DESCRIPTION OF THE DRAWINGS

To complement the description that will be made below and in order to help a better understanding of the characteristics of the invention, in accordance with a preferred example of its practical implementation, a set of plans is attached as an integral part of said description. where, for illustrative and non-limiting purposes, the following has been represented:

Figures 1.1 and 1.2 show the structure of the encapsulation of the magnets of the cathodes of types 1 and 2.

Figure 2 represents the schematic of the type 1 cathode with flat emitter and magnetic field for plasma operation without heater, in its lateral gas inlet variant.

Figure 3 shows the diagram of the type 2 cathode with flat emitter and magnetic field for operation with plasma without heater, in its central gas inlet variant.

Figure 4 shows the structure of the encapsulation of the type 3 and 4 cathode magnets.

Figure 5 illustrates the architecture and design components of the type 3 cathode with cylindrical emitter and magnetic field for plasma operation without heater in lower gas inlet variant.

Figure 6 shows the architecture and design components of the type 4 cathode with cylindrical emitter and magnetic field for plasma operation without heater in side gas inlet variant.

Figure 7 shows the configuration of a type 5 cathode with a cylindrical emitter without a magnetic field for plasma operation in a lateral gas inlet variant and with a lateral “keeper” auxiliary electrode.

Figure 8 shows the first of the hollow cylindrical emitter electrode configurations, specifically the type 6 cathode type with hollow cylindrical emitter without magnetic field for plasma operation in a central gas inlet variant and with an auxiliary “keeper” electrode. superior.

Figure 9.1 illustrates the type 7 cathode with a hollow cylindrical emitter without a magnetic field for plasma operation in a central gas inlet variant and with a lateral “keeper” auxiliary electrode.

Figure 9.2 illustrates a device similar to the previous one with the variant of the gas outlet, which in this case takes place through holes located in the clamping base of the emitter, instead of through the upper central hole of the emitter.

Figure 10 represents the schematic of the configuration of a type 8 cathode with a hollow cylindrical emitter without a magnetic field for plasma operation in a lateral gas entry variant and with a double auxiliary “keeper” electrode (central and lateral).

Figure 11 shows the diagram of a type 9 cathode with a hollow cylindrical emitter without a magnetic field for vacuum operation and with a double auxiliary “keeper” electrode (central and lateral).

Figure 12 represents the schematic of a current intensifying device to be coupled on top of any electron generating device.

Figure 13.1 represents the scheme of a cathode based on a filament coated with C12A7:e-electride material with the techniques described, especially by spray or nebulizer.

Figure 13.2 shows the previous cathode integrated with a control grid to modulate the electron beam emitted by a variable direct current source (42).

Figure 14.a details the structure of a PEM electrolyzer with the cathode based on C12A7:e electride while Figure 14.b shows an AEM electrolyzer, Likewise with the cathode based on C12A7:e electride.

Figure 15 details the structure of a PEM fuel cell with the cathode based on C12A7:e electride.

Figure 16 details the structure of a high-temperature SOEC solid oxide electrolyzer with the C12A7:e-based cathode electrified using an H+ proton conduction ceramic membrane.

Figure 17 details the structure of a high-temperature SOFC solid oxide fuel cell with the cathode and anode based on C12A7:e “electride” and a ceramic H+ proton conduction membrane.

Figures 18.1 and 18.2 detail a scheme that describes the deposition of the electride from the “electride solution” described in the present invention using the spray or nebulization technique, assisted or not by high voltage.

Figure 19 illustrates the “forced” improvement or post-treatment procedure.

DETAILED DESCRIPTION OF THE DRAWINGS.

In the figures described above the following references have been used:

1. Outer hole of the ionization chamber

2. Ionization chamber

3. Walls of the ionization chamber made of temperature-resistant insulating material. 4. Base of the ionization chamber.

5. Electron emitting electrode (C12A7:e electride)

6. Auxiliary electrode (INOX, Mo, Ta, or graphite)

7. Gasket/insulating washer between the emitter and auxiliary electrodes

8. External ring magnet (Samarium-Cobalt)

9. Internal cylindrical magnet (Samarium-Cobalt)

10. Non-ferromagnetic material magnet separator ring

11. Top Magnet (Samarium Cobalt)

12. Bottom Magnet (Samarium Cobalt)

13. Magnet container and field closure with temperature resistant ferromagnetic material.

14. Base of the emitting electrode and external enclosure of magnets and heatsink

15. Gas inlet tube (INOX)

16. Gas outlet hole

17. Emitting electrode signal connector (Mo, Ta, or graphite)

18. Auxiliary electrode signal connector (Mo, Ta, or graphite)

19. Auxiliary electrode walls (Al, Mo, Ta, or graphite)

20. Emitting electrode signal connector insulating tube

21. Auxiliary electrode signal connector insulating tube

22. Heatsink

23. Emitting electrode holding base

24. Insulating structure between emitter and auxiliary electrodes

25. Outlet insulating tube

26. Emitting electrode insulating tube

27. Upper insulating washer

28. Bottom insulating washer

29. Auxiliary electrode insulating layer (insulating paste/paint)

30. Gas inlet pipe insulation tube

31. Base for holding the emitting electrode (Mo, Ta or graphite)

32. Insulating tube for the emitting electrode holding base

33. Internal auxiliary electrode (Mo, Ta or graphite)

34. Internal auxiliary electrode signal connector (Mo, Ta or graphite)

35. Internal auxiliary electrode signal connector insulating tube

36. W, Ta, Mo filament coated with electride and with subsequent treatment.

37. Insulating support

38. Filament heating control resistor

39a. Floating pulsed (square wave) power supply for filament feeding (heating).

39b. Pulsed power supply (square wave) for polarization of the negative filament with respect to ground and with the possibility of offset.

40. Complete cathode body with insulating grid.

41. Grid (Ta, Mo)

42. Grid Potential Control Source

43. Grid current control resistor

44. PEM/AEM electrolyzer and PEM cell cathode

45. Substrate (DOF)

46. (a,b) PEM membrane (46.a) and AEM membrane (46.b)

47. PEM/AEM electrolyzer and PEM cell anode

48. C12A7:e- electride deposited on substrate by various techniques

49. Electrolyzer cathode electrode/cell SOEC, SOFC

50. C12A7:e- solid electride (undeposited)

51. Thin (deposited) or solid ceramic proton conduction membrane

52. SOEC electrolyzer cathode and SOFC cell

53. SOEC electrolyzer anode and SOFC cell

54. Spray or nebulizer control

55. Spray or nebulizer with solution with C12A7:e electride

56. Substrate to deposit the material C12A7:e electride

57. High voltage source (10 to 20 KV)

58. Material C12A7:e- electride, solid or deposited on a substrate, to be treated in post-process

59. Active connection cable (Mo, Ta, W). Connected to a piece of graphite in contact with the C12A7:e- electride material. It will connect to negative or DC negative pulses.

60. Ground connection cable (Mo, Ta, W) (camera ground). All crucibles are grounded.

61. Alumina insulating tube for active cable (59) and ground (60)

62. Inner graphite crucible

63. Outer graphite crucible

64. Graphite piece for contact with C12A7:e- electride and with the active cable (59) 65. Graphite lids of the graphite crucibles

66. Pure alumina insulators

67. Graphite support with cable contact (60) with ground connection.

Figures 1.1 and 1.2 show the structure of the encapsulation of the cathode magnets of types 1 and 2. In them, the internal cylindrical magnet (9) is located in the center of the magnet separator ring (10) and the external annular magnet (8) on the outside of that separator ring, and their north-south poles are oriented so that the directions of the magnetic field are those shown in figures 1a or 1b . The set of these three pieces is inserted into a piece of ferromagnetic stainless steel (type AISI 446 or similar) that contains the set of magnets and closes its magnetic field so that it is limited to the area immediately above the magnets, and so as not to cause magnetic interactions in the rest of the cathode structure and surrounding devices.

Figure 2 represents the schematic of the type 1 cathode with flat emitter and magnetic field for plasma operation without heater, in its lateral gas inlet variant. The part of the auxiliary keeper electrode (6) located above the emitter electrode (5) maintains most of its electrically insulated surface by being covered by the insulating piece (7) so that it is only exposed to the current of emitted electrons a central crown of said “keeper” of a few millimeters or tenths of a millimeter. Likewise, the upper surface of said “keeper” is covered by the insulating piece (4), which is thus also electrically insulated. The combination of both insulations considerably reduces the current absorbed by the “keeper” compared to that emitted by the cathode. Likewise, the thickness of the “keeper” should be as minimal as possible (less than 1 millimeter and ideally hundreds of nano meters or one micron if it is deposited on the insulator with metal deposition techniques by evaporation, sputtering, PLD, etc. ). The design of this cathode also makes the size of the exit hole of the device independent of the size of the “keeper” hole by placing above the latter an ionization chamber constructed of insulating material so that it does not extract electrons or ions from the gas that is ionized inside, and with a section perpendicular to the gas flow that is much larger in relation to the gas inlet and outlet orifice, which will cause an overpressure of gas in said chamber (Venturi effect) that favors the creation of plasma with low gas flow regimes (measured in sccm, less than 2 sccm). The magnets used will be made of samarium cobalt to withstand temperatures around 350 °C that are reached at the cathode when operating in a plasma environment without reaching the Curie temperature and losing efficiency. On the other hand, the magnetic field created by this set of magnets is perpendicular in a circular crown corresponding to the space between magnets to the electric field created between the cathode and the "keeper", so the Lorentz force is maximum, leaving the electrons confined. in said area, or at least with longer helical-shaped trajectories with a residence time greater than that of straight trajectories, creating an area of high electron charge density that, colliding with the atoms (or molecules) of the gas in question, cause a high degree of ionization.

Figure 3 shows the diagram of the type 2 cathode with flat emitter and magnetic field for operation with plasma without heater, in its central gas inlet variant. As indicated above, this is a variant of the previous cathode in which it is only modified. The indications and comments related to the electrical insulation of the auxiliary “keeper” electrode described for the type 1 design in Figure 2 are common for this variant shown in Figure 3. Likewise, the indications and comments related to the ionization chamber with electrically insulated walls and those related to the behavior associated with the magnetic field generated by the set of magnets.

Figure 4 shows the structure of the encapsulation of the magnets of the cathodes type 3 and 4. The upper (6) and lower (7) annular magnets are inserted and placed in the positions indicated in Figure 4 inside the piece ferromagnetic stainless steel (type AISI 446 or similar) that acts simultaneously as a magnet container and field closure element (13) and as an auxiliary “keeper” electrode element (6). The orientation of the north-south poles of these magnets face each other so that the direction of the magnetic field is one of those shown in figure 4. The set of these three pieces closes the magnetic field inside the element 6+13 and prevents magnetic interactions from causing the rest of the cathode structure and surrounding devices. It is very convenient to apply a thin layer of electrical insulation to the interior walls of the assembly that makes up the ionization chamber in order to reduce the return to mass of the electrons emitted from the emitting cathode and those generated by the ionization of the gas.

Figure 5 illustrates the architecture and design components of the type 3 cathode with cylindrical emitter and magnetic field for plasma operation without heater in the lower gas inlet variant. The electric field between the emitting electrode and the auxiliary “keeper” electrode, which determines the direction of the electric field, is perpendicular to the magnetic field generated by the magnets shown in figure 4. In this way, the electrons will trace a helical path which will increase the residence time in the ionization chamber and therefore the probability of collision with the neutrals of the gas that It is injected through the gas inlet tube and its consequent ionization accompanied by the emission of electrons.

Figure 6 shows the architecture and design components of the type 4 cathode with cylindrical emitter and magnetic field for plasma operation without heater in side gas inlet variant. Like the previous configuration in Figure 5, the electric field between the emitting electrode and the auxiliary “keeper” electrode is perpendicular to the magnetic field generated by the magnets shown in Figure 4. The helical path that the emitted electrons will experience will increase the time spent in the ionization chamber and therefore the degree of ionization of the gas and its corresponding additional generation of electrons.

Figure 7 shows the configuration of a type 5 cathode with a cylindrical emitter without a magnetic field for plasma operation in a lateral gas inlet variant and with a lateral “keeper” auxiliary electrode. This is a simplification of the architecture of the previous cathode shown in Figure 6, where the magnets and the effects of the magnetic field they generate have been dispensed with, designed for applications in which the size and mass of the cathode are larger. determinants than the current gain that may occur through the longer residence time of the electrons in the ionization zones of the gas.

Figure 8 shows the first of the hollow cylindrical emitter electrode configurations, specifically the type 6 cathode type with hollow cylindrical emitter without magnetic field for plasma operation in a central gas inlet variant and with an auxiliary “keeper” electrode. superior. This configuration is the most common in traditional hollow cathode designs, although the configuration included in this invention has its own specific differential characteristics. The hollow cylinder of the emitting electrode is not inserted into a hollow cylinder of graphite or other conductive material, but is surrounded by a thin insulating layer that electrically isolates it from the "keeper", avoiding losses of ions and electrons due to neutralization in the walls. It also differs from other traditional hollow cathode designs in that no heating element is incorporated since the device starts the emission from room temperature thanks to the effect of the charge coupling mechanism through pulses between the "keeper" and the emission current with the That operates.

Figure 9.1 illustrates the type 7 cathode with a hollow cylindrical emitter without a magnetic field for plasma operation in a central gas inlet variant and with a lateral “keeper” auxiliary electrode, which is a configuration similar to the previous one but without the insulating layer. between the emitting electrode and the side walls of the auxiliary keeper electrode, which increases the emission surface of the emitting electrode and therefore the current density generated with respect to the configuration of the type 6 cathode in figure 8. In addition, it incorporates as an additional element an upper enclosure that forms an ionization chamber that increases the relative pressure of the gas by having a section perpendicular to the flow much larger than the inlet and outlet orifices (Venturi Effect) made or covered with electrically insulating material that prevents the capture of electrons by part of said element.

Figure 9.2 illustrates a device similar to the previous one with the variant of the gas outlet, which in this case takes place through holes located in the clamping base of the emitter, instead of through the upper central hole of the emitter.

Figure 10 represents the schematic of the configuration of a type 8 cathode with a hollow cylindrical emitter without a magnetic field for plasma operation in a lateral gas entry variant and with a double auxiliary “keeper” electrode (central and lateral), which is an evolution of the previous cathode in which the gas is injected laterally at the height of the ionization chamber in order to take advantage of the internal part of the hollow emitting cylinder as an additional surface for electron emission by means of a second auxiliary electrode facing the emitting electrode on its face. interior that is polarized in the same way as the lateral auxiliary electrode.

Figure 11 shows the diagram of a type 9 cathode with a hollow cylindrical emitter without a magnetic field for vacuum operation and with a double auxiliary “keeper” electrode (central and lateral). This device is used for systems that require vacuum thermionic emission without gas injection and allows its integration into existing engines (“thrusters”) that require neutralization and equip traditional hollow cathodes, allowing the maximization of the emission surface that can be obtained with the same dimensions of the traditional hollow cathode that it replaces.

Figure 12 shows the schematic of a current intensifying device for be attached on top of any electron generating device. The magnetic field it generates increases the residence time of the electrons emitted by the device to which it is coupled, by generating helical trajectories, thus increasing the degree of ionization of the gas that is injected from its side.

Figure 13.1 represents the scheme of a cathode based on a filament coated with C12A7:e-electride material with the techniques described, especially by spray or nebulizer. The innovation comes in the form of coating and subsequent treatment and, above all as in the rest of the cases, in the form of pulsed and negative polarization with respect to mass (source 39.b). In this case, in addition, the filament is heated with an equally pulsed source, in this case floating, connected between the ends of the filament and a control resistor (current limiting). Pulsed heating offers excellent performance, both in emission and stability. The combination of pulsed heating with pulsed polarization is the best possible combination. Both signals are synchronized (square waves). In this particular case, filament, the treatment after the deposition of the C12A7:e- “electride” material is carried out directly with the device already made, during the first heating and emission ramps. It is advisable to use at least two initial hours for this treatment, ideally 8 hours, at temperatures no higher than 900°C, or more ideally 850°C.

Figure 13.2 shows the previous cathode integrated with a control grid to modulate the electron beam emitted by a variable direct current source (42).

Figure 14.a details the structure of a PEM electrolyzer in which protons (H+) are conducted from the anode to the cathode. In Figure 14.b, an AEM membrane is used through which OH- ions are conducted from the cathode to the anode. In both cases, the cathode is based on C12A7:e electride. In this case the electride is deposited on a conventional GDL (Gas Diffusion Layer) or equivalents such as high conductivity carbon fibers, carbon fibers and nanotubes or active carbon fibers. The deposition is mainly by means of the spray or nebulization technique of the electride solution described in the present invention, assisted or not with high voltage. Traditional procedures such as PLD, pulsed sputtering, PVD, etc. can be used. Subsequently, the forced reduction treatments described are applied and it is assembled as if it were the original cathode, including the corresponding electrode. If the reduction procedures (especially forced) were not applied after the deposition of the electride on the carbon fiber membrane, the performance would be much lower, which is considered, in this case, a key point of the invention. The cathode-anode separation membrane is of low temperature proton conductivity (“Nafion” type) or alkaline conductivity of OH- groups (“Fumapem” type).

Figure 15 details the structure of a PEM fuel cell (conduction of H+ protons from the anode to the cathode) with the cathode based on C12A7:e electride. In this case the electride is deposited on a conventional GDL (Gas Diffusion Layer) or equivalents such as high conductivity carbon fibers, carbon fibers and nanotubes or active carbon fibers. The deposition is mainly by means of the spray or nebulization technique of the electride solution described in the present invention, assisted or not with high voltage. Traditional procedures such as PLD, pulsed sputtering, PVD, etc. can be used, but spray deposition is clearly superior. As with electrolyzers, subsequent forced reduction treatment is essential, including the substrate itself in said process, as in the previous case.

Figure 16 details the structure of a high temperature SOEC solid oxide electrolyzer with the cathode based on C12A7:e electride. In this case, the electride is massively deposited on high-conductivity carbon fibers, carbon fibers and nanotubes, or active carbon fibers. The deposition is mainly by means of the spray or nebulization technique of the electride solution described in the present invention, assisted or not with high voltage. Traditional procedures such as PLD, pulsed sputtering, PVD, etc. can be used, although the deposition is not as massive and, therefore, poorer in quantity of material, as with spray. Subsequently, forced reduction treatments are applied, including the substrate in said process and it is assembled as if it were the original cathode, including the corresponding electrode. The membrane, in this case, is a ceramic with proton conductivity (H+) based on BaZrO ₃ or oxygen ions (O=) based on YSZ (Yttria Stabilized Zirconia). In this case, protonic (BaZrO ₃ ) is chosen due to its better performance.

Figure 17 details the structure of a high temperature SOFC solid oxide fuel cell with the anode based on C12A7:e “electride” to produce the decomposition of fuels such as NH3 or CH4 at high temperature, where the material works as an excellent catalyst for the dissociation of said compounds. In turn, it is added to the cathode of the battery to facilitate the transfer of electrons to the H+ ions that arrive through the membrane. That is, in this case the electride is used both at the anode for the decomposition of NH3, CH4 in combination with the usual anode catalysts (Pt, Ni among others) and at the cathode for its usual function of transferring electrons. In this case, the “electride” is massively deposited on high-conductivity carbon fibers, carbon fibers and nanotubes, or active carbon fibers. The deposition is mainly by means of the spray or nebulization technique of the electride solution described in the present invention, assisted or not with high voltage. Traditional procedures such as PLD, pulsed sputtering, PVD, etc. can be used, although the deposition is not as massive and, therefore, poorer in quantity of material, as with spray. Subsequently, forced reduction treatments are applied, including the substrate in said process and it is assembled as if it were the original cathode, including the corresponding electrode. The membrane, in this case, is ceramic with special proton conductivity (H+) based on BaZrO ₃ . Said membrane is preferred over that of oxygen ions because in this way the formation of NOx is avoided as the water in the cathode does not come into contact with active Nitrogen ions in the anode, a result of the decomposition of NH3.

Figures 18.1 and 18.2 detail a scheme that describes the deposition of the electride from the “electride solution” described in the present invention using the spray or nebulization technique, assisted or not by high voltage. The nebulizer can be conventional or controlled syringe type so that, through the controller, precise amounts of material are deposited per cm2, in addition to guaranteeing homogeneity. In turn, the nebulizer holder system can have an X-Y position numerical control device so that the electride can be deposited on large substrates while maintaining homogeneity. Finally, the high voltage polarization between the (metallic) outlet of the nebulizer and the substrate allows the particles to be electrostatically charged and produce a better diffusion effect while maintaining homogeneity. Subsequently, the high activation treatments are applied and it is assembled as if it were the original cathode, including the corresponding electrode. The membrane is ceramic with special proton conductivity.

Figure 19 illustrates the “forced” improvement or post-treatment procedure.

The C12A7:e- material to be treated (58), either in solid form or deposited on a substrate, is electrically isolated by pieces of pure alumina (66) in a graphite crucible (62), maintaining only contact with an additional piece. (64) also made of graphite which, in turn, is connected with a cable (59), normally made of Mo, Ta or W. This cable will be the “active” or negative pulses. The first graphite crucible (62), containing the material, is introduced into a second crucible (63) also made of graphite, both having their respective lids (65), also made of graphite. The active cable (59) has an insulating sheath (61) made with an alumina tube, to be able to pass through the covers and the entire assembly while maintaining the insulation. The set of crucibles rests on a piece of graphite (67), square or circular, to which another connection is made with a cable (60) of the same materials Mo, Ta or W, also insulated with an alumina tube ( 61) to avoid possible unwanted short circuits. The crucibles are in electrical contact with each other and with the graphite base and its cable that will be connected to ground. The system for non-forced treatment is the same, without having the cables and connection elements used in the forced case.

PREFERRED EMBODIMENT OF THE INVENTION

As previously stated, the present invention incorporates a series of novelties in different phases of the construction of the final devices, grouped into the following concepts:

1. - Procedures for improving the synthesized material C12A7:e- “electride” , applied to the final solid samples of different shapes (such as discs or hollow cylinders) or to the depositions made on substrates or supports depending on the type of application.

2. - Design of different cathode architectures for electron emission that take advantage of the characteristics of the C12A7:e “electride” material, the material improvement procedures (forced reduction) and the pulsed polarization procedures for the stabilization of the emission defined in the prior invention application P 202130778 dated August 10, 2021.

3. - Use of special substrates and procedures for the deposition of the C12A7:e- “electride” material on said substrates.

The use of specific substrates and supports to deposit the material instead of being used in a solid form has very significant advantages in terms of resistance to fractures and breaks under conditions of mechanical and thermal stress, overcoming the drawbacks of a ceramic material when used. in solid parts, especially in the aerospace field (neutralizers and propellants). It is also necessary when used as a cathode for electrolyzers and fuel cells since the cathodes are usually manufactured precisely from carbon-graphite fibers that contain the catalyst, make the electrical connection and allow the exchange of gases (known as GDL or Gas Diffusion Layer). ).

1.- Procedures for improving the material C12A7:e- “electride” from its synthesis.

Once the C12A7 ceramic has been synthesized and reduced to “electride” C12A7:e- by any of the published procedures, some of them included in different patents, a maximum reduction of the resulting material can be caused by the addition of elements with an oxidation enthalpy higher than those corresponding to the elements usually used, that is, Ca, C and Ti, such as V (vanadium), Gd (Gadolinium), Sm (Samarium), Ce (Cerium), Sr (Strontium) and Ba (Barium). ). The addition of hydrogen in the reduction process significantly improves the results. This improved procedure, which we will call "simple thermal reduction" is carried out by subjecting the material (both solid and deposited, including the corresponding substrate) to a process between 1150 and 1300 °C, better at 1250 °C, in a graphite crucible, wrapped in graphite sheets with a mixture of graphite and a reducing element, this element being any of the above in powder (less than 10 microns of grain) between said sheets. The proportion by weight of graphite/element can be up to 50%/ 50%, better 75%/25%. The previous crucible is introduced into an additional larger crucible, also made of graphite, both with a lid. It is necessary to create a high vacuum in the furnace beforehand (P≤10-5 Torr) Argon (Ar) can be added to avoid excessive evaporation up to a pressure greater than 10-4 Torr and less than 10-3 Torr. The time depends, fundamentally, on the temperature. For the range 1150-1200°C at least 10h and for the range 1200-1300°C at least 6 hours. The reduction can be assisted by hydrogen, in which, instead of using only Ar, a mixture is used (measuring in sccm or cubic centimeters per minute of gas through gas mass flow controllers) to 50% Ar and H ₂ , or 75% Ar and 25% hydrogen and up to 90% Ar and 10% hydrogen, maintaining the previous background pressure levels. In this case it They obtain excellent results even in the low temperature range, which is always the most indicated.

Forced reduction: It consists of an innovative technique to forcefully move the reduction reaction which, under normal conditions, will depend on the temperature, the reducing elements and compounds used and the reaction time. The technique consists of adding a negative polarization to the sample to be reduced (enhancement) both at DC (continuous) and pulsed levels, in order to “force” the emission of negative ions and/or electrons once the activation temperature that is required is reached. allows the replacement of negative ions with electrons supplied by the electrical connection, producing the desired process, that is, the replacement of oxygen ions located in the center of the cells with electrons, which constitutes the main characteristic of the “electride”. Since polarization forces the reaction from the activation temperature (between 550°C and 950°C depending on the initial state of the ceramic, lower the more partially reduced it is), excellent reductions are achieved at lower temperatures and this fact It allows the use of a wider range of substrates (especially based on carbon fiber, carbon nanotubes, etc.) that perfectly withstand the low temperature range. In other words, this technique allows the reduction temperature of the material to be considerably lowered to a range between 550°C and 950°C, and can reach 1050°C or 1150°C if the substrates allow it.

The C12A7:e- sample to be treated, whether it is a solid form or a substrate with the deposited material, is electrically isolated from the crucibles by using alumina or any non-conductive refractory material that does not evaporate or have metallic or alkaline contamination. (ideally pure alumina) making a connection with a cable (Mo, Ta, W, Pt) also isolated from the crucibles by means of alumina tubes (Fig. 19). In this case, the crucibles will not contain the graphite sheets that surround the samples used in thermal reductions, nor is the graphite powder and the reducing element necessary, although if used, special care must be taken not to short-circuit the sample with the crucible. The larger graphite crucible rests on a graphite base that is connected with a cable (Mo, Ta, W, Pt). Both cables are connected through a bulkhead from the vacuum chamber to the outside. The sample lead will be the active signal (always negative), while the crucible lead will be connected to ground or always more positive than the active signal (ideally ground, with zero reference potential). The active signal (in contact with the sample to be treated) a direct current source will be connected either to the negative pole while the ground will be connected to the positive pole of said source, which must necessarily be floating (poles isolated from the ground), applying a voltage between 10 and 200 V (preferably 100 V) or to a square wave generator of the same amplitude (10 to 200 V, preferably 100 V) with a cyclic ratio of 50%, others can be used depending on the measured current, in general a lower ratio with currents large and greater relationship with small currents. The pulses must be negative with respect to mass. Once it has been verified that there are no shorts (zero current at room temperature), the heating ramp begins, as in the previous cases, both with Ar only and with Ar and hydrogen at 50%. With this procedure, the maximum temperature is 1150°C given the risk of melting of the material, working very well at a temperature between 550 and 1100°C and even better between 750°C and 950°C. The time will depend on the nature of the samples, with a minimum of 2 hours. Current will be detected from the temperature at which the emission begins to be relevant. A good indicator of complete treatment is to observe that the current does not increase significantly in the last 30 to 60 minutes of observation or even if it decreases slightly. Lower temperatures, 600, 700, 800 and 900°C, may be used when substrates are particularly temperature sensitive.

2.- Design of different cathode architectures for electron emission

The set of cathodes that are collected and described in this invention can be grouped by the combinations of the following characteristics of these devices:

• Shape of the emitting electrode: flat, hollow cylindrical, cylindrical.

• Use of magnetic fields

• Operating environment: vacuum or ionized gas (plasma).

• Type of heating: with or without heater.

Adopting different variants depending on the gas entry place for those who work in a plasma environment.

Taking into account this classification, the 9 types of cathode design that are included in this invention are the following:

1. Cathode with flat emitter and magnetic field for plasma operation without heater in lateral gas inlet variant (Figures 1.1, 1.2 and 2).

2. Cathode with flat emitter and magnetic field for plasma operation without heater in central gas inlet variant (Figure 3)

3. Cathode with cylindrical emitter and magnetic field for plasma operation without heater in lower gas inlet variant (Figure 4 and 5)

4. Cathode with cylindrical emitter and magnetic field for plasma operation without heater in lateral gas inlet variant (Figure 4 and 6)

5. Cylindrical emitter cathode without magnetic field for plasma operation in lateral gas inlet variant and with lateral “keeper” auxiliary electrode (Figure 7) 6. Hollow cylindrical emitter cathode without magnetic field for plasma operation in inlet variant central gas and with upper “keeper” auxiliary electrode (Figure 8)

7. Hollow cylindrical emitter cathode without magnetic field for plasma operation in central gas inlet variant and with lateral “keeper” auxiliary electrode (Figure 9.1 and 9.2)

8. Hollow cylindrical emitter cathode without magnetic field for plasma operation in lateral gas inlet variant and with double auxiliary “keeper” electrode (central and lateral) (Figure 10)

9. Hollow cylindrical emitter cathode without magnetic field for vacuum operation and with double auxiliary “keeper” electrode (central and lateral) (Figure 11)

10. Cathode based on depositing the C12A7:e- material on a filament of W, Ta, Mo (Figures 13.1 and 13.2) using the spray techniques with or without potential described below. (Figures 18.1 and 18.2)

All the cathodes included in this invention can be started from room temperature, without the need to equip any heating element, by applying the charge coupling mechanism through negative pulses between C12A7:e-electride material and the “keeper”, saving the dielectric surface. and its drawbacks already described in the previous invention with application number: 202130778 dated 08/18/2021.

In the previous designs, solid forms of the synthesized and machined material are used: hollow cylinders, disks or any other form of the material synthesized and machined in said form. In the case of cathodes based on flat discs, said disc of solid C12A7:e- material can be replaced by a thin disc of activated carbon fiber, including carbon nanotubes or not in its composition, to which has been deposited the material C12A7:e- “electride” with the techniques described in the following section and has been subjected to the improvement procedure by forced reduction (ideal) or simple reduction. This substitution is very important given that the solid material (solid discs) has ceramic characteristics, that is, rigidity and fragility, negative aspects for its reliable use in aerospace applications where the materials have to withstand vibrations, thermal and mechanical stress situations and others. factors that make us distrust materials that can fracture, as in fact happens. By having a flexible carbon fiber, it is impossible to break or fracture in any extreme condition since they do not have to withstand traction and are not affected by vibrations or thermal stress. Even in these circumstances, carbon fiber is precisely one of the most reliable and resistant materials known, but it is very difficult and requires a lot of energy to emit electrons. The combination C12A7:e- “electride” deposited on carbon fiber is ideal to have the electron emission characteristics of the material while avoiding its weak points as a ceramic material.

Additionally, a cathode based on a filament (W, Ta, Mo) coated with the C12A7:e material is presented. especially indicated for emission of electrons in vacuum by temperature. In this case, the novelty lies in how to coat the filament with the material, according to the techniques described in the following section and its subsequent treatment with special forced reduction for this case and, above all, in the form of combined pulsed and DC excitation in addition to keep the filament always more negative than the zero potential reference (mass), a technique used in all the electron-emitting cathodes presented (Figures 13.1 and 13.2)

Finally, a current intensifying device is presented to be coupled on top of any electron generating device. The magnetic field it generates increases the residence time of the electrons emitted by the device to which it is coupled, by generating helical trajectories, thus increasing the degree of ionization of the gas that is injected from its side. The result is a greater degree of ionization of the gas and, therefore, electrons available for extraction in a beam towards the anode (Fig. 12).

3.- Use of special substrates and procedures for the deposition of the material C12A7:e- “electride” on said substrates

The use of specific substrates and supports to deposit the material instead of being used in a solid form has very significant advantages in terms of resistance to fractures and breaks under conditions of mechanical and thermal stress, overcoming the drawbacks of a ceramic material when used. in solid parts, especially in the aerospace field (neutralizers and propellants). Furthermore, this format is necessary when it is used as a cathode for electrolyzers and fuel cells since the cathodes are usually made precisely of carbon-graphite fibers that contain the catalyst, make the electrical connection and allow gas exchange (known as GDL or “GDL”). Gas Diffusion Layer"). The substrates considered are grouped into the following types:

Carbon-based substrates: carbon nanotubes, activated carbon, conventional carbon fiber, graphite and all their forms.

Metallic substrates such as Ti, Mo, Ta, W and semiconductors such as Si, Ge, SiC, GaAs.

Transition substrates (insulator-semiconductor) depending on temperature, especially Y ₂ O ₃ , YSZ (“Yttria stabilized Zirconia), V ₂ O5, Ta ₂ O5, TiO ₂ , ZrO ₂ , La ₂ O ₃ , SrTiO ₃ , BaTiO ₃ and BaZrO ₃ . These substrates can act as a separating membrane for the cathode and anode in the case of electrolyzers and high temperature cells (SOEC and SOFC respectively).

Insulators such as Al ₂ O ₃ , HfO ₂ , SiO ₂ , MgO, AlN. In the case of non-conductive substrates and with certain semiconductors, it is necessary to enable a conductive layer between the material and the substrate, ideally Mo, Ta, Ti, W, using any deposition technique, for the polarization of the cathode.

The most convenient deposition techniques are:

• For thin film: PLD (Pulsed Laser Deposition), which is the most reliable in terms of the purity of the deposited material, maintaining the stoichiometry of C12A7:e- “electride”, sputtering in a pulsed regime and never in DC ( direct current) and thermal evaporation in a high vacuum oven (P≤10-5 Torr), at temperatures above 1250°C. The previous techniques are not described in the present invention since they are not the subject of a patent except for identifying the PLD technique as the most reliable.

• Thick layers of material and carbon substrates (active carbon fibers, carbon nanotubes and all their derivatives) (Figures 18.1 and 18.2). Ideal for the electron emission devices detailed above, replacing the solid piece (disc or even hollow tubes) with carbon fiber sheets with a large amount of “electride” deposited. It is, as described, necessary for electrolyzers and fuel cells. The layers of matter are deposited using simple spray (nebulizer) and electro spray techniques, forcing a high voltage (>10KV) between the controlled nebulizer and the substrate, which allows a more uniform and controlled distribution than by gravity alone. These techniques are known and widely used. The innovation consists of the preparation of the ideal “electride” suspension to be used using this technique and, above all, its subsequent forced reduction treatment. The suspension to be nebulized consists of a solution formed by: the material C12A7:e- “electride” pulverized into fine particles (between 0.1 and 10 microns depending on the need for fine or very fine particles). fine particles), Titanium (Ti), also in fine particles of the order of the micron, in a proportion with respect to the “electride” of 1%, 1.5%, 2%, 3% by weight (better 1.5%) in comparable grains (better up to 1 micron), well mixed (in a ball mill or similar) using methanol, ethanol, propylene glycol or similar as a solvent, never water or hydroxides based, with a proportion of solvent that allows the fluidity of the solution through from the nebulizer or spray (ideally, ≤25% by weight of solute, that is, the powdered C12A7:e material mixed with the Titanium).

In the case of using the material deposited on a substrate, by any technique, a reducing thermal post-treatment is necessary (forced or not, more convenient forced and especially forced in the case of using carbon fiber substrates) due to the degradation suffered by The material “electrides” when ground into fine grains (the dielectric surface ratio increases in relation to the available material the finer the grinding, given that each particle has its surface isolated by said dielectric). In this way, it is necessary to regenerate the material already incorporated into the substrate as much as possible, also achieving better integration, especially from the point of view of electrical conductivity, in conductive substrates, especially those based on carbon fiber and graphite. . This treatment is essential for the correct functioning of the material in the different cathode configurations.

The treatments can be specific, including the substrate, to obtain the final substrate-electride system deposited, to later be used in the different devices (emitting cathodes for neutralizers and propellants, electrolyzer cathodes and fuel cells) or perform the treatment once the cathode is assembled, as is the case of the emitter cathode based on a filament coated with “electride” and eventually some of the cathodes for neutralizers and propellants. In no case can it be done once mounted on the cathodes used in electrolyzers and fuel cells, especially at low temperatures, given that there will be no way to carry out the forced reduction without damaging the systems, taking into account the temperatures used (greater than 650° C).

The use of the material as a catalyst for electrolyzers and fuel cells, the C12A7:e- “electride” material has two characteristics that make it ideal as a cathode in said devices:

^o A low work function that allows the exchange of electrons in the cathode-ion direction with very low energies, lowering the overpotential of the cathode-ion interface, essential for good electrode performance

^o Excellent adsorption properties of Hydrogen and even more so in ionic form H+ (protons) that allows improving the emission through field effect (Schottky).

4.- New electrolyzers and fuel cells PEM/AEM and high temperature SOEC and SOFC.

The application of the C12A7:e-electride material to conductive and non-conductive substrates, detailed in the previous sections, allows the creation of low-temperature PEM/AEM electrolyzers and low-temperature PEM cells where the material is used as a catalyst to replace expensive elements. and scarce ones such as Pt, Pd, Ir, Ru, etc. in the cathode in a completely new way, as discussed in the study of the state of the art.

Since the material can operate at high temperatures (up to 1150°C) it is also ideal for cathodes of electrolyzers and high temperature oxide fuel cells (SOEC and SOFC respectively) that work between 500°C and 950°C where it is also It is incorporated into the anode in the case of SOFC cells where the fuel is ammonia (NH3) or natural gas (CH4) or methanol/ethanol. This is because the electride acts as a catalyst in the dissociation of the previous compounds, especially ammonia (NH3), which directly obtains the H ₂ that is normally used as fuel. In this case, the use of the electride in the anode is carried out in combination with usual anode catalysts responsible for the ionization of H ₂ , generating H+ protons, being fully compatible. The advantage of these high temperature devices, in addition to their superior performance than the PEM/AEM type, is that they can work with different fuels (H ₂ , NH3, Methanol/Ethanol, natural gas CH4, etc.) and even have tolerance to impurities and other compounds (such as CO ² ) that poison (passivate) the Pt-type catalysts. Precisely, at high temperatures, the material is an active electron emitter without the need for any type of additional energy, which allows the electrode overpotential to be lowered. which is one of the parameters with the most impact on the performance of electrolyzers and fuel cells. The most relevant objective is the realization of direct ammonia (NH3) fuel cells as well as CH4, methanol/ethanol, from which Hydrogen is extracted for normal operation with said fuel. Since proton conduction membranes will preferably be used in the case of high temperature SOFC cells, we refer to them as SOFC-H. The fundamental advantages of using proton conduction membranes are, on the one hand, greater conductivity than with oxygen ions (O=) and, above all, the non-formation of NOx (N ₂ O, NO, NO ₂ ) since The water (steam) is confined in the cathode away from the ions resulting from the dissociation of NH3 at the anode, thus avoiding the formation of said NOx compounds. If an oxygen ion conduction membrane is used, water (steam) is formed at the anode along with the dissociation of NH3, inevitably forming NOx compounds.

References used:

[1] S. Kim and H. Hosono. Philosophical Magazine. Vol 32. N 19-21. 2596-2628. (2012).

[2] Y. Toda, Y. Kubota, M. Hirano, H. Hirayama and H Hosono. ACS nano Vol 5. N 3.

1907-1914. (2011).

[3] PV Ong, H Hosono, and P V. Sushko J. Phys. Chem. C 1236030 (2019).

[4] J Fabian-Plaza, G Meiro, A Post, R Pérez-Casero, FJ Palomares, P Tejedor, S Naghdi, A Várez, and G Sánchez-Arriaga Acta Astronaut. 177806 (2020).

[5] M. Goebel and I. Katz. Fundamentals of electric propulsion: Ion and Hall Thrusters. JPL-NASA (2008).

Claims (19)

1.- Procedure for improving the synthesized material C12A7:e- “electride”, which starts from a C12A7 ceramic synthesized and reduced to “electride” C12A7:e- to obtain cathodes, is characterized in that the synthesized C12A7 ceramic or the ceramic reduced to “electride” C12A7:e- is subjected to a forced reduction, in which oxygen ions are replaced by electrons through the negative polarization of the material to be reduced in a DC or pulsed regime, with respect to the mass or reference of zero voltage; It has been foreseen that this process can be carried out on the newly synthesized base material, the ground material, the material deposited on a substrate including said substrate or a complete assembly that includes the material, the substrate and other constituent elements of the cathode. 2§.- Procedure for improving the synthesized material C12A7:e- “electride”, according to claim 1§, characterized in that it consists of carrying out a decrease in the temperature and/or process time with respect to the conventional reduction process (substitution of oxygen ions by electrons), reducing and integrating in the same process not only the material but the substrate or a larger assembly that may be sensitive to temperature, a temperature drop that goes from the range of 950°C to 1250°C up to the range 650°C to 950°C. 3§.- Procedure, according to claims 1§ and 2§, characterized in that it is determined to use a pulsed signal instead of direct current (DC), always with negative polarity, to avoid instabilities and achieve stable and smooth operation. material degradation, using an auxiliary electrode (keeper) to facilitate charge coupling. 4§.- Procedures for improving the synthesized material C12A7:e- “electride”, according to claims 1§, 2§ and 3§, characterized in that an ionization chamber with a significantly smaller entrance and exit section is used. than the section of the chamber itself to produce an overpressure due to the Venturi effect, where the electrode interacts in a gaseous medium or plasma, having foreseen that by virtue of said overpressure the plasma operates with low gas supply regimes and even lower potential for cathode necessary to maintain the plasma, having foreseen that the walls of the chamber are electrically insulated or covered with material insulator to prevent the neutralization of electrons and ions. 5- .- Procedure, according to claims 1§ and 2§ characterized in that the material is deposited on the substrates with various techniques, preferably using the "spray" or nebulized mode, with or without high voltage assistance to obtain the solution at nebulize formed by the base material C12A7:e- “electride” and a non-aqueous solvent, including reducing additives. 6- .- Procedure, according to claims 1-, 2- and 5-, characterized in that substrates of the carbon fiber type are used, activated or with graphite additives and carbon nanotubes, as well as ceramic materials to which the material according to claim 2- and is subsequently treated for improvement according to claim 1-. 7- .- Cathode, according to claim 6-, characterized in that it is applied in the aerospace sector. 8- .- Cathode, according to claim 6-, characterized in that it is applied to electrolyzers and fuel cells, both low temperature (PEM or alkaline type) and high temperature (SOEC and SOFC respectively), where the GDL (Gas Diffusion Layer) that forms the cathode, normally based on carbon (carbon fiber, graphite paper and the like) and ceramic substrates, contains C12A7:e- “electride” material deposited and treated according to claims 1-, 2-, 3- and 4-, acting as a catalyst in said devices. 9- .- Cathode, according to claims 6- and 8-, characterized in that it is applied in water purification systems based on electrolysis. 10- .- Cathode, according to claim 8-, characterized in that when it comes to cathodes used in electrolyzers and fuel cells, both low temperature (PEM or alkaline type) and high temperature (SOEC and SOFC respectively), and in water purification systems based on electrolysis, in which noble metals (Pt, Pd, Ir, Ru) are replaced. 11- .- Cathode, according to claims 9- and 10-, characterized in that it consists of a cathode with flat emitter and magnetic field for plasma operation without heater in side gas inlet variant. 12§.- Cathode, according to claims 9§ and 10§, characterized in that it consists of a cathode with a flat emitter and magnetic field for plasma operation without heater in the lower-central gas inlet variant. 13§.- Cathode, according to claims 9§ and 10§, characterized in that it consists of a cathode with a cylindrical emitter and magnetic field for plasma operation without heater in a lower-central gas inlet variant and with a lateral “keeper” auxiliary electrode. . 14§.- Cathode, according to claims 9§ and 10§, characterized in that it consists of a cathode with a cylindrical emitter and magnetic field for plasma operation without heater in a lateral gas inlet variant and with a lateral “keeper” auxiliary electrode. 15§.- Cathode, according to claims 9§ and 10§, characterized in that it consists of a cylindrical emitter cathode without a magnetic field for plasma operation in a lateral gas entry variant and with a lateral “keeper” auxiliary electrode. 16§.- Cathode, according to claims 9§ and 10§, characterized in that it consists of a cathode with a hollow cylindrical emitter without a magnetic field for plasma operation in a central gas inlet variant and with an upper “keeper” auxiliary electrode. 17§.- Cathode, according to claims 9§ and 10§, characterized in that it consists of a cathode with a hollow cylindrical emitter without a magnetic field for plasma operation in a central gas inlet variant and with a lateral “keeper” auxiliary electrode. 18§.- Cathode, according to claims 9§ and 10§, characterized in that it consists of a cathode with a hollow cylindrical emitter without a magnetic field for plasma operation in a gas inlet variant through lower holes in the base for holding the emitter and with auxiliary “keeper” electrode on the side. 19§.- Cathode, according to claims 9§ and 10§, characterized in that it consists of a cathode with a hollow cylindrical emitter without a magnetic field for plasma operation in variant with central gas inlet and with double auxiliary “keeper” electrode (central and lateral). twenty - . - Cathode, according to claims 9§ and 10§, characterized in that it consists of a hollow cylindrical emitter cathode without magnetic field for vacuum operation and with a double auxiliary “keeper” electrode (central and lateral). 21 - .- Cathode, according to claims 9- and 10-, characterized in that it consists of a cathode based on depositing the C12A7:e- “electride” material on a filament of W, Ta, Mo, using pulsed signals both to heat the filament to establish its potential with respect to the mass reference (zero potential) which will always be negative. Incorporation of a polarized grid as part of the cathode to control the intensity of the emitted electron beam. 22 - Ånode, according to claims 6- and 8-, in the case of SOFC-H cells (high temperature with proton conduction membrane) where C12A7:eelectride is used as a catalyst for the dissociation of the fuel when it is not Hydrogen , especially ammonia (NH3) as well as natural gas (CH4) and methanol/ethanol, obtaining Hydrogen from said fuel in the cell itself. 23-.- Ånode, according to claim 22-, for a direct NH3 fuel cell without NOx production, being of the SOFC-H type (high temperature with proton conduction membrane).