JP4804350B2 - Electrode and method for producing the electrode - Google Patents

Description

  The present invention relates to an electrode, a method for producing the electrode, and use thereof.

  Electrodes for use in industrial electrolysis, water electrolysis, and other electrolysis methods, such as platinum group metal oxide-coated electrodes, usually have low electrical resistance at high currents. However, such electrodes usually have a short durability.

  U.S. Pat.No. 4,568,568 states that the particles are heated at a temperature up to 6000 ° C. and then collide with the support at a high speed, thereby partially melting the particles, resulting in a layer of uniform thickness on the support. A method for plasma spray coating of particles on an associated electrode support is disclosed. These particles do not give an increased surface area to the resulting electrode.

  The present invention addresses the disadvantages of the prior art and aims to provide a particle-coated electrode with increased specific surface area, stability and performance, which has numerous applications. It is another object of the present invention to provide a convenient and reliable method for bonding particles to an electrode in a cost effective manner. It is a further object of the present invention to provide a method that allows particles to be adhered to an electrode without deforming the shape of the particles.

  In the present invention, a binder dispersion containing a conductive or semiconductive oxide precursor is attached to an electrode support, and a conductive or semiconductive oxide coating is formed on the electrode support from the precursor. Conductive titanium oxide and electrode particles are attached to the conductive or semiconductive oxide coating, and the electrically conductive titanium oxide and electrode particles are adhered to the formed conductive or semiconductive oxide coating. To an electrode manufacturing method.

  The term “dispersion” as used herein includes, in addition to conventional dispersions, suspensions and slurries of particles, and also, for example, solutions of oxide-forming precursors.

  According to one embodiment, the conductive or semiconductive oxide is bonded by decomposing the precursor, preferably by pyrolyzing it. However, this precursor may also be precipitated and oxide from an initial precursor, which may be, for example, a hydroxide or hydrated oxide of titanium or other suitable metal Can result in the generation of

  The electrode support material can maintain its physical integrity during manufacture and, for example, its subsequent use in an electrolytic cell, preferably any conductive material that can be resistant to alkaline and acidic electrolytic solutions. It may be of a sex element. Suitable electrode support materials include conductive metals such as copper, nickel, valve metals such as titanium, tantalum, zirconium or niobium, and alloys or mixtures thereof, preferably titanium or alloys thereof.

  The form of electrode support used is not critical. Suitable electrode supports may take the form of, for example, flat sheets or plates, curved surfaces, convoluted surfaces, stamped plates, woven wire screens, expanded mesh sheets, rods, or tubes. . However, the electrode support preferably has a planar shape, most preferably in the form of a sheet, mesh or plate.

  The electrode support can be roughened by sand blasting, grit blasting, chemical etching or the like. The use of chemical etchants is known and such etchants include the strongest inorganic acids such as hydrochloric acid, sulfuric acid, nitric acid and phosphoric acid, but also organic acids such as oxalic acid.

  The conductive or semiconductive oxide precursor (which may be in the form of a dissolved salt or acid) may be dissolved in an acidic aqueous or organic dispersion or a mixture thereof. Preferred organic dispersions include alcohols such as iso-propanol, n-propanol, or butanol, or mixtures thereof. The organic salt or acid is preferably dissolved in an organic solvent, most preferably an alcohol as described herein, while the inorganic salt and inorganic acid are preferably dissolved in a substantially aqueous dispersion.

  The organic binder dispersion and / or aqueous binder dispersion preferably has a pH of about 0.5 to about 4, most preferably about 0.5 to about 2. The binder dispersion preferably has a metal concentration of from about 10 g metal / l to about 200 g metal / l, most preferably from about 20 g metal / l to about 30 g metal / l.

  The precursor may be any suitable organic salt or organic acid and / or inorganic salt or inorganic acid. This precursor is preferably a mixture of titanium, tantalum, tin, antimony, indium and tin salts, preferably at least two organic salts or organic acids and / or inorganic salts and / or inorganic acids of titanium and tantalum. Preferably butyl titanate or ethyl titanate and butyl tantalite or ethyl tantalite are used in combination. According to one embodiment, butyl titanate and butyl tantalite are used in combination. The titanium to tantalum molar ratio is suitably from about 9: 1 to about 7: 3, preferably from about 9: 1 to about 8: 2. Organic salt and / or organic acid precursors are preferred. This is because their corresponding conductive or semiconductive oxides can be formed at low temperatures. This is preferred. This is because the low heating temperature prevents the electroconductive titanium oxide particles from being oxidized so much, resulting in higher electrical conductivity.

  According to one embodiment, the electrically conductive titanium oxide is suspended in the binder dispersion. As a result, a conductive or semiconductive oxide coating that binds evenly dispersed electrically conductive titanium oxide will be formed on the electrode support. This may be advantageous for better adhesion of subsequently deposited electrode particles. If this is the case, the electrically conductive titanium oxide particles (which are preferably smaller than the electrode particles) surround the electrode particles and thus, due to the increased contact area, the electrode support, the electrically conductive oxide This is because it provides better adhesion between the titanium particles and the electrode particles.

  According to one embodiment, the precursor is pyrolyzed at a temperature from about 300 ° C to about 600 ° C, more preferably from about 450 ° C to about 500 ° C. However, if the precursor is a colloidal solution, such as a slightly alkaline alcohol solution of alkoxy-titanium and tantalum in ammonia, the decomposition can occur at a temperature from about 300 ° C to about 450 ° C. This low temperature is probably possible due to the fact that colloidal hydroxide or hydrated oxide solutions can be converted to oxides by dehydration.

  According to one embodiment, electrically conductive titanium oxide and electrode particles suspended in an aqueous or organic dispersion, preferably an aqueous dispersion, are formed on the formed conductive or semiconductive oxide coating. To be attached.

  According to one embodiment, the electrically conductive titanium oxide and electrode particles are suspended in a binder dispersion resulting in adhesion of the electrode particles to the oxide coating formed from the precursor.

  In order to obtain a thicker conductive or semiconductive oxide coating, the deposition operation can be repeated preferably at least twice, most preferably at least four times. The thickness of the oxide is preferably from about 2 μm to about 4 μm.

  According to one embodiment, the electrically conductive titanium oxide is about 0.1 μm to about 100 μm, more preferably about 1 μm to about 20 μm, more preferably about 5 μm to about 20 μm, most preferably about 5 μm to about 10 μm. Particle size up to.

The electrically conductive titanium oxide is substantially magneli phase (including various oxides such as Ti ₄ O ₇ and Ti ₅ O ₉ ) and / or TiO depending on where the manufactured electrode is used. It is preferable that

  Magnesium phase titanium oxide is preferably used to produce electrodes for use in strongly acidic electrolyte solutions such as sulfuric acid or nitric acid because of its ability to withstand corrosive environments. TiO is preferably used in electrodes for use in electrolytes having a pH of about 1.5 or higher.

Electrically conductive titanium oxide can be prepared from a conventional sintered mixture of commercially available rutile or anatase phase non-conductive titanium oxide (TiO ₂ ) and titanium metal in vacuum at temperatures between 1000 ° C. and 1500 ° C.

Electrically conductive titanium oxide can be prepared by mixing finely pulverized TiO ₂ in the rutile phase in an agate mortar followed by sintering. The resulting electrically conductive titanium oxide powder contains a mixture of Ti ₃ O ₅ , Ti ₄ O ₇ and / or Ti ₅ O ₉ .

As used herein, the term “electrode particles” is electrically conductive and has catalytic activity. The material is diamond, for example, boron-doped diamond, titanium oxide, for example, magnetite phase titanium oxide (Evonex ^™ ), tin dioxide, magnetite (Fe ₃ O ₄ ), Ni-ferrite, β-lead dioxide (β-PbO ₂ ) BN, WC, SiC, and / or mixtures thereof, preferably diamond. These electrode particles suitably have a size from about 0.5 μm to about 100 μm, preferably from about 1 μm to about 20 μm, and most preferably from about 5 μm to about 10 μm.

  Diamond particles may be obtained from conventional diamond synthesis methods at elevated temperatures and pressures.

  According to one preferred embodiment, two different layers are applied on a conductive or semiconductive oxide coating to obtain a lower layer suitably comprising electrically conductive titanium oxide and an upper layer of electrode particles to stabilize the electrode. Increase adhesion and adhere these electrode particles more firmly.

  According to a preferred embodiment, a roughened, blasted and pickled electrode support is applied with a binder dispersion comprising a titanium oxide semiconductive oxide precursor, which is subsequently heated to about 500 ° C. It is decomposed at a temperature up to about 600 ° C. to produce a conductive oxide, followed by depositing a slurry of electrically conductive titanium oxide having a titanium content of about 3 to about 20 times the metal content of the binder dispersion. Subsequently, heat treatment is performed at 400 to 500 ° C. for 10 minutes. Subsequently, in a second step, a dispersion containing about 50% by weight electrode particles and about 50% by weight electrically conductive titanium oxide is deposited on the oxide coating and heat treated to produce electrically conductive titanium oxide and electrodes. The particles are adhered to the formed titanium oxide coating. According to one embodiment, this second step is repeated at least twice, preferably at least three times.

  The resulting electrode can be further stabilized in a vacuum or inert atmosphere, for example, in argon gas at a temperature from about 500 ° C. to about 600 ° C.

  Furthermore, the present invention relates to an electrode obtained from the method described herein.

  The present invention further comprises an electrode support, a conductive or semiconductive oxide bonded to the electrode support, and electrode particles and electrically conductive titanium oxide bonded to a conductive or semiconductive oxide coating. It relates to an electrode. The electrode support, conductive or semiconductive oxide, electrically conductive titanium oxide, and electrode particles are preferably as described herein.

  According to one embodiment of the invention, the conductive or semiconductive oxide may comprise several oxide layers, preferably two oxide layers.

According to one embodiment, the first layer of oxide coating comprises electrically conductive titanium oxide and electrode particles. The first layer oxide coating may comprise from about 10% to about 70%, preferably from about 40% to about 60% by weight of electrode particles. This first layer may comprise from about 20% to about 80%, preferably from about 30% to about 60% by weight of electrically conductive titanium oxide. The second layer suitably comprises from about 30% to about 80%, preferably from about 50% to about 70%, by weight of electrode particles. The remaining part of the second layer is preferably covered with electrically conductive titanium oxide. According to one embodiment, the electrically conductive titanium oxide content is from about 20% to about 70% by weight, preferably from about 30% to about 50% by weight, based on the weight of the oxide coating. The adhesion of the electrode particles is preferably about 10 g to about 500 g, more preferably about 50 g to about 100 g per 1 m ^{2 of the} electrode support area. Deposition of electroconductive titanium oxide is from electrode support area 1 m ² per about 5g to about 200 g, further preferably from about 10g to about 100 g.

  It has been found that the electrodes obtained in this way can remain stable even in corrosive atmospheres at high potentials and currents greater than 2V relative to NHE. This is due to the fact that the oxide produced from the binder dispersion adheres the particles of electrically conductive titanium oxide, which in turn, in combination with the oxide coating formed from the binder dispersion, adheres the electrode particles. It may be because.

According to one embodiment, the electrode is diamond, tin dioxide, magnetite (Fe ₃ O ₄ ), nickel ferrite, β-lead dioxide, titanium oxide, BN, WC, SiC, Si ₃ N ₄ or mixtures thereof, preferably Has a second layer comprising electrically conductive electrode particles of titanium oxide and / or diamond, most preferably diamond.

  The electrodes can take any shape. However, planar electrodes will be preferred for most applications. This electrode preferably contains no bimetallic spinel in any of its layers. It is preferred that the electrode does not contain any platinum group metals or oxides thereof. This is because it may lead to passive problems.

  The invention also relates to the use of electrodes in an electrolytic cell for water treatment, secondary batteries, eg secondary batteries in redox flow batteries, and electrolysis methods in electrolytic ozone production.

  In particular, electrodes with boron-doped diamond electrode particles are used to generate oxygen, ozone, hydrogen peroxide, hydroxyl radicals due to their good electrical conductivity as p-type semiconductors; water electrolysis, water treatment, And can be used as an anode in electro-organic synthesis. As the cathode, the electrode is preferably used for electro-organic synthesis, generation of OH radicals, various oxidation methods, redox flow batteries for power storage, and standardization of power consumption.

  Now that the invention has been described, it will be clear that the invention may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, but all modifications that are obvious to those skilled in the art are intended to be included within the scope of the invention. The following examples further illustrate how the described invention may be practiced without limiting the scope of the invention.

To prepare an electrode support, a 1 mm thick titanium plate was grit blasted to a surface roughness of Ra = 5 μm and pickled with sulfuric acid. A binder solution containing TiCl ₄ and TaCl ₅ dissolved in a 10 wt% HCl solution was applied to the electrode support and heated at 540 ° C. for 10 minutes. The coating and heating steps were repeated 4 times to obtain a 0.2 μm oxide film on a tantalum and titanium oxide electrode support with a molar ratio of Ta to Ti of 1: 9. A slurry was prepared by suspending electrically conductive titanium oxide powder in a HCl solution of penta-butyl tantalite and tetra-butyl titanate having a molar ratio of Ti: Ta of 8: 2. The weight ratio of electrically conductive titanium oxide to total Ti and Ta metal content in the binder dispersion was 20: 1. The dispersion was stirred and applied to the oxide film. After drying, the electrode was first heated at 60 ° C. for 10 minutes and then heated at 450 ° C. for 10 minutes. To obtain a coating of a porous oxide of 60 g / m ² having a protruding specific surface area of the support area 1 m ² per 10 m ^2. To the porous oxide coating was applied a slurry prepared from 50% by weight of electrically conductive titanium oxide and 50% by weight of boron doped electrically conductive diamond powder having an average particle size of 7-10 μm. Subsequently, the slurry was dried and heated at 450 ° C. for 10 minutes. This adhesion of the slurry was repeated once, followed by the same heat treatment. The obtained electrode has been shown to work well with continuous electrolysis at a current density of 1 A / dm ² .

An electrode was prepared by attaching electrically conductive titanium oxide to a titanium electrode support prepared in the same manner as in Example 1. The electrically conductive titanium oxide powder was suspended in a binder dispersion containing titanium trichloride and penta-butyl tantalite having a 9: 1 titanium to tantalum molar ratio. The weight ratio of electrically conductive titanium oxide to total Ti and Ta metal content in the binder dispersion was 20: 1. The binder dispersion was applied to an electrode support which was subsequently dried in air at room temperature, subsequently dried at 60 ° C. and heat treated at 500 ° C. This application of the binder solution was repeated three times. An electrically conductive titanium oxide layer (substantially Ti ₄ O ₇ ) was formed under the same conditions as in Example 1, and the coating amount was 60 g per m ² of the support area. The electrically conductive titanium oxide layer is then formed from magnetic phase titanium oxide particles having a size of 5-10 μm, these are suspended in the slurry, then coated as in Example 1 and heat treated at 450 ° C. for 10 minutes. did. This operation was repeated three times to obtain a total of 50 g of titanium metal deposited per 1 m ^{2 of} the support area. The electrical conductivity of the electrode was slightly higher than that of Example 1 due to the electrode material. This active surface area was increased to 20 m ² per m ² of electrode support area. Next, continuous electrolysis was performed at a current density of ² A / dm2.

  The electrode of Example 2 was prepared except that the electrode particles were 9: 1 molar tin to antimony rutile phase tin oxide and antimony oxide particles. This electrode was tested in a sulfuric acid electrolyte containing 100 ppm phenol and shown to work. This is because the degradation of phenol could be observed.

An electrode was prepared according to Example 1 except for diamond particles substituted with TiO particles. Continuous electrolysis was performed at a current density of 3 A / dm ² in H ₂ SO ₄ solution.

An electrode support was prepared as shown in Example 1. A binder dispersion was prepared by mixing an acidic solution of tetrabutoxy-titanate and pentaboxytantalite in an 8: 2 molar ratio and then neutralizing it with ammonia. The solution turned cloudy and colloidal precipitation was detected. Then butyl alcohol was added to the turbid liquid containing hydrated titanium-tantalum co-oxide to adjust the total metal content of the liquid to 15 g / l. The resulting liquid had a viscosity of 10-20 centipoise. The electrically conductive titanium oxide was then mixed into the dispersion and subsequently applied to the electrode support with a brush. After drying, the support was heat-treated at 300 ° C. in an air atmosphere to obtain 50 g of electrically conductive titanium oxide deposited per 1 m ^{2 of} the support area. Then 70% by weight of electrically conductive titanium oxide and 30% by weight of β-PbO ₂ particles (the average particle size was 10-12 μm) were coated on the oxide coated support. The support was then dried and heat treated. Then, 20 g of β-lead dioxide per 1 m ² was deposited. The obtained electrode had a surface area of 8 m ² per m ² of electrode support and could be used as an anode in continuous electrolysis at a current density of 10 A / dm ² .

A tin dioxide particle electrode was prepared by the same method as in Example 5, except that β-lead dioxide was replaced by tin dioxide. The tin dioxide was obtained by coprecipitation of 90 mol% tin tetrachloride (SnCl ₄ ) and antimony pentachloride in ethyl alcohol by neutralization with ammonia. About 1 mol% iridium chloride was then added to the dispersion. The dispersion was then dried and subsequently heat treated at 400 ° C. for 30 minutes in air. A black electrically conductive tin dioxide was obtained. Next, the tin dioxide was crushed and ground with agate milk bee. The resulting tin dioxide powder was simultaneously deposited on the electrode support with electrically conductive titanium dioxide. The surface area of the electrode was the electrode support 1 m ² per 7-8 m ^2. This electrode was then used at a current density of ² A / m ² and was shown to work well.

Claims (9)

Attaching a binder dispersion containing a conductive or semiconductive oxide precursor to the electrode support;
Forming a conductive or semiconductive oxide coating from the precursor on the electrode support;
Adhering a dispersion of electrically conductive titanium oxide and electrode particles having a particle size of 5 μm to 100 μm to the conductive or semiconductive oxide coating; and the electrically conductive titanium oxide and electrode particles, Adhering to the formed conductive or semiconductive oxide coating, wherein the precursor comprises at least two organic salts or acids and / or titanium, tantalum, tin, antimony, indium and tin salts and / or Or selected from inorganic salts or mixtures of inorganic acids,
The electrode particles include diamond, tin dioxide, magnetite (Fe ₃ O ₄ ), Ni-ferrite, β-lead dioxide, magneto-phase titanium oxide, BN, WC, SiC, Si ₃ N ₄ or mixtures thereof;
The method for producing an electrode, wherein the electrically conductive titanium oxide particles are smaller than the electrode particles.   The method of claim 1, wherein the binder dispersion comprises a precursor of titanium oxide or tantalum oxide.   The method of claim 1, wherein the binder dispersion comprises a precursor of titanium oxide and tantalum oxide.   The method according to claim 1, wherein the precursor is pyrolyzed at a temperature of 300 ° C. to 600 ° C.   The method according to claim 1, wherein the electrically conductive titanium oxide is substantially TiO.   The method according to any one of claims 1 to 5, wherein the electrode particles include a magnesium phase titanium oxide.   The method according to claim 1, wherein the electrode particles include diamond. Electrode support, is adhered to the electrode support, and, of titanium oxide, tantalum oxide, tin oxide, conductive is selected from at least two antimony oxide and oxidized indium arm or semiconductive oxide coating, and wherein An electrode comprising electrode particles having a particle size of 5 μm to 100 μm bonded to a conductive or semiconductive oxide coating and electrically conductive titanium oxide, said electrode particles comprising diamond, tin dioxide, magnetite ( Fe ₃ O ₄ ), Ni-ferrite, β-lead dioxide, magneto-phase titanium oxide, BN, WC, SiC, Si ₃ N ₄ or a mixture thereof, and the electrically conductive titanium oxide particles are the electrode particles Smaller than the electrode.   The electrode according to claim 8, wherein the electrode particles include a magnesium phase titanium oxide.