JP3782835B2 - Method for producing photolysis catalyst - Google Patents
Method for producing photolysis catalyst Download PDFInfo
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- JP3782835B2 JP3782835B2 JP32168194A JP32168194A JP3782835B2 JP 3782835 B2 JP3782835 B2 JP 3782835B2 JP 32168194 A JP32168194 A JP 32168194A JP 32168194 A JP32168194 A JP 32168194A JP 3782835 B2 JP3782835 B2 JP 3782835B2
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- 239000003054 catalyst Substances 0.000 title claims description 18
- 238000006303 photolysis reaction Methods 0.000 title claims description 15
- 238000004519 manufacturing process Methods 0.000 title claims description 9
- 230000015843 photosynthesis, light reaction Effects 0.000 title claims description 8
- 150000001875 compounds Chemical class 0.000 claims description 35
- 239000004065 semiconductor Substances 0.000 claims description 16
- 238000005341 cation exchange Methods 0.000 claims description 15
- -1 salt compound Chemical class 0.000 claims description 13
- 229910021645 metal ion Inorganic materials 0.000 claims description 8
- 238000005342 ion exchange Methods 0.000 claims description 7
- 229910044991 metal oxide Inorganic materials 0.000 claims description 6
- 150000004706 metal oxides Chemical class 0.000 claims description 6
- 238000001782 photodegradation Methods 0.000 claims description 4
- 238000000034 method Methods 0.000 claims description 3
- 230000001678 irradiating effect Effects 0.000 claims description 2
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 27
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N Iron oxide Chemical compound [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 description 20
- 239000010410 layer Substances 0.000 description 11
- 239000007864 aqueous solution Substances 0.000 description 7
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 7
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 6
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 6
- 239000000243 solution Substances 0.000 description 5
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 4
- 229910052739 hydrogen Inorganic materials 0.000 description 4
- 239000011229 interlayer Substances 0.000 description 4
- VLKZOEOYAKHREP-UHFFFAOYSA-N n-Hexane Chemical compound CCCCCC VLKZOEOYAKHREP-UHFFFAOYSA-N 0.000 description 4
- 239000011882 ultra-fine particle Substances 0.000 description 4
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 3
- 230000003197 catalytic effect Effects 0.000 description 3
- 239000001257 hydrogen Substances 0.000 description 3
- 150000002500 ions Chemical group 0.000 description 3
- 229910052742 iron Inorganic materials 0.000 description 3
- 229910052760 oxygen Inorganic materials 0.000 description 3
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 description 2
- 229910002367 SrTiO Inorganic materials 0.000 description 2
- 229910010413 TiO 2 Inorganic materials 0.000 description 2
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 2
- 238000009835 boiling Methods 0.000 description 2
- 239000001569 carbon dioxide Substances 0.000 description 2
- 229910002092 carbon dioxide Inorganic materials 0.000 description 2
- 150000001768 cations Chemical class 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- QSHDDOUJBYECFT-UHFFFAOYSA-N mercury Chemical compound [Hg] QSHDDOUJBYECFT-UHFFFAOYSA-N 0.000 description 2
- 229910052753 mercury Inorganic materials 0.000 description 2
- 239000003960 organic solvent Substances 0.000 description 2
- 239000001301 oxygen Substances 0.000 description 2
- 239000000843 powder Substances 0.000 description 2
- 230000009257 reactivity Effects 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 229910015902 Bi 2 O 3 Inorganic materials 0.000 description 1
- 238000002441 X-ray diffraction Methods 0.000 description 1
- 150000001242 acetic acid derivatives Chemical class 0.000 description 1
- 230000002378 acidificating effect Effects 0.000 description 1
- 150000003973 alkyl amines Chemical class 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 229910000416 bismuth oxide Inorganic materials 0.000 description 1
- 238000006555 catalytic reaction Methods 0.000 description 1
- 150000001805 chlorine compounds Chemical class 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- TYIXMATWDRGMPF-UHFFFAOYSA-N dibismuth;oxygen(2-) Chemical compound [O-2].[O-2].[O-2].[Bi+3].[Bi+3] TYIXMATWDRGMPF-UHFFFAOYSA-N 0.000 description 1
- 238000004455 differential thermal analysis Methods 0.000 description 1
- 238000004090 dissolution Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 150000002823 nitrates Chemical class 0.000 description 1
- QGLKJKCYBOYXKC-UHFFFAOYSA-N nonaoxidotritungsten Chemical compound O=[W]1(=O)O[W](=O)(=O)O[W](=O)(=O)O1 QGLKJKCYBOYXKC-UHFFFAOYSA-N 0.000 description 1
- IOQPZZOEVPZRBK-UHFFFAOYSA-O octylazanium Chemical compound CCCCCCCC[NH3+] IOQPZZOEVPZRBK-UHFFFAOYSA-O 0.000 description 1
- 239000007800 oxidant agent Substances 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 230000001699 photocatalysis Effects 0.000 description 1
- 230000001443 photoexcitation Effects 0.000 description 1
- 238000000634 powder X-ray diffraction Methods 0.000 description 1
- 238000005215 recombination Methods 0.000 description 1
- 230000006798 recombination Effects 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 230000005476 size effect Effects 0.000 description 1
- KKCBUQHMOMHUOY-UHFFFAOYSA-N sodium oxide Chemical compound [O-2].[Na+].[Na+] KKCBUQHMOMHUOY-UHFFFAOYSA-N 0.000 description 1
- 229910001948 sodium oxide Inorganic materials 0.000 description 1
- 238000010532 solid phase synthesis reaction Methods 0.000 description 1
- 150000003467 sulfuric acid derivatives Chemical class 0.000 description 1
- 239000000725 suspension Substances 0.000 description 1
- 229910001930 tungsten oxide Inorganic materials 0.000 description 1
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/30—Hydrogen technology
- Y02E60/36—Hydrogen production from non-carbon containing sources, e.g. by water electrolysis
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- Light Receiving Elements (AREA)
- Catalysts (AREA)
Description
【０００１】
【産業上の利用分野】
本発明は、光エネルギーを化学エネルギーへ変換する光分解用触媒の製造方法に関し、特に太陽光によって効率的に水の光分解又は二酸化炭素の還元を可能にする触媒を製造する方法に関する。
【０００２】
【従来の技術及び発明が解決しようとする課題】
近年、半導体を電極として用い、水等を光分解することにより水素を製造する方法が見出され、光エネルギーを化学エネルギーに変換する方法が提案されている。このように、水を水素と酸素に光分解することのできる半導体の代表的なものとして、ＴｉＯ2 、ＳｒＴｉＯ3 及びＣｄＳ等が知られている。
【０００３】
しかしながら、ＴｉＯ2 、ＳｒＴｉＯ3 等水を水素と酸素に完全に光分解できる半導体は、いずれも３ｅＶ以上の大きなバンドギャップを有し、太陽光はほとんど利用できないという問題がある。太陽エネルギーの利用効率の向上のためには、３ｅＶ未満のバンドギャップを有する半導体が望まれるが、一般的にバンドギャップの小さい半導体は触媒活性が小さく、また溶液中で溶解しやすいため、化学的な安定性に劣るという欠点がある。
【０００４】
バルクの酸化鉄（Ｆｅ2 Ｏ3 ）はバンドギャップが２．３ｅＶと小さく、光溶解もなく安定で、太陽光の利用効率が約１７％と高い。しかし、バルク状のものは触媒反応サイトの表面積が小さく、反応特性が低い。また、反応性の向上を目指して超微粒子化を図る今までの努力では、量子サイズ効果によりハンドギャップが増大し、半導体の光触媒特性が変わってしまい、反応特性の向上につながらない。
【０００５】
したがって、本発明の目的は、超微粒子化してもハンドギャップがほとんど上昇せず、太陽光で効率的に作用する光分解用触媒及びそれを製造する方法を提供することである。
【０００６】
【課題を解決するための手段】
上記課題に鑑み鋭意研究の結果、本発明者は、鉄等の金属イオンを含む塩化合物と、陽イオン交換性層状化合物とをイオン交換した後、金属イオンを含む化合物をアルカリ性化合物水溶液に分散させ、紫外線を照射すると、酸化物の超微粒子化が可能であるとともに、ハンドギャップがほとんど上昇しないことを発見し、本発明を完成した。
【０００７】
太陽光により励起される金属酸化物半導体を陽イオン交換性層状化合物に包接して光分解用触媒を製造する本発明の方法は、金属イオンを含む塩化合物と、前記陽イオン交換性層状化合物とをイオン交換した後、金属イオンを含む化合物をアルカリ性化合物水溶液に分散させ、紫外線を照射することにより分解し、もって層間に金属酸化物を包接した光分解用触媒を製造することを特徴とする。
【０００８】
以下、本発明を詳細に説明する。
〔１〕光分解用触媒の構成
本発明の光分解用触媒は、太陽光により励起される半導体(a) を陽イオン交換性層状化合物に包接してなる。
【０００９】
(a) 半導体
半導体は、太陽光等の可視光により励起される金属酸化物半導体であり、具体的には鉄酸化物（Ｆｅ2 Ｏ3 ）、ビスマス酸化物（Ｂｉ2 Ｏ3 ）、タングステン酸化物等で、好ましくは鉄の酸化物である。上記半導体は、ハンドギャップが３ｅＶ以下であり、太陽光で光分解反応を触媒するが、反応性が低いため、以下説明するイオン交換性層状化合物の層間に包接して金属酸化物を超微粒子化する。
【００１０】
(b) 陽イオン交換性層状化合物
陽イオン交換性層状化合物は、層状の格子間に有する陽イオンを、化合物の外部の陽イオンと交換できればいかなるものでもよいが、具体的にはＨ2 Ｔｉ4 Ｏ9 、Ｈ4 Ｎｂ6 Ｏ17、ＨＢｉＮｂ2 Ｏ7 、Ｈ2 Ｌａ2 Ｔｉ3 Ｏ10 及びＨＮｂ3Ｏ8 等が好ましく、特にＨ2 Ｔｉ4 Ｏ9 及びＨ4 Ｎｂ6 Ｏ17が好ましい。
【００１１】
上記陽イオン交換性層状化合物は、Ｋ2 Ｔｉ4 Ｏ9 、Ｋ4 Ｎｂ6 Ｏ17、ＫＢｉＮｂ2 Ｏ7 、Ｋ2 Ｌａ2 Ｔｉ3 Ｏ10 及びＫＮｂ3 Ｏ8 の粉末を0.1 〜10Ｎの塩酸等の酸性水溶液中に１〜１５０時間分散させ、層間のＫ+ をＨ+ にイオン交換することにより得られる。
【００１２】
〔２〕光分解用触媒の製造方法
本発明の光分解用触媒は、以上説明した半導体を、陽イオン交換性層状化合物に包摂させてなるが、その具体的な製造方法を説明する。
【００１３】
(1) 陽イオン交換性層状化合物への包接
Ｋ2 Ｔｉ4 Ｏ9 、Ｋ4 Ｎｂ6 Ｏ17、ＫＢｉＮｂ2 Ｏ7 、Ｋ2 Ｌａ2 Ｔｉ3 Ｏ10及びＫＮｂ3 Ｏ8 等の層状化合物を塩酸等の水溶液中に分散させて得られたＨ2 Ｔｉ4 Ｏ9 、Ｈ4 Ｎｂ6 Ｏ17、ＨＢｉＮｂ2 Ｏ7 、Ｈ2 Ｌａ2 Ｔｉ3 Ｏ10及びＨＮｂ3 Ｏ8 等の陽イオン交換性層状化合物を、ｎ−ヘキサン等の有機溶媒又は水に分散させる。次いでｎ−Ｃ8 Ｈ17ＮＨ2 やｎ−Ｃ3 Ｈ7 ＮＨ2 等のアルキルアミンを添加し、室温以上かつｎ−ヘキサン等の有機溶媒又は水の沸点未満の温度下で１時間〜１週間反応させ、層間のＨ+ をアルキルアンモニウムイオンとイオン交換する。
【００１４】
アルキルアンモニウムイオン含有層状化合物を金属イオンを含む塩化合物の水溶液に懸濁する。このような金属イオンを含む塩化合物として、例として鉄の場合、Ｆｅ3+の塩化合物、［Ｆｅ3 （ＯＣＯＣＨ3）7 ＯＨ・２Ｈ2 Ｏ］+ の塩化合物等が挙げられる。塩化合物は、硝酸塩、硫酸塩、酢酸塩、塩化物等を指す。この懸濁液を室温以上かつ水溶液の沸点（約100℃）未満の温度下で１時間〜１週間反応させ、層間のアルキルアンモニウムイオンと、Ｆｅ3+又は［Ｆｅ3 （ＯＣＯＣＨ3 ）7 ＯＨ・２Ｈ2 Ｏ］+ とをイオン交換する。その化合物を分離させた後、Ｆｅ3+の場合、水酸化ナトリウム等のアルカリ性化合物水溶液に分散させて加水分解し、［Ｆｅ3 （ＯＣＯＣＨ3 ）7 ＯＨ・２Ｈ2 Ｏ］+ の場合では、水酸化ナトリウム等のアルカリ性化合物水溶液に分散させ、水銀ランプなどの光源により、紫外線を０．５〜２４時間照射して、又は過酸化水素等の酸化剤を添加し、０．５〜２４時間反応して、層間のＦｅ3+又は［Ｆｅ3 （ＯＣＯＣＨ3 ）7 ＯＨ・２Ｈ2 Ｏ］+ をＦｅ2 Ｏ3 ・ｎＨ2 Ｏ（ただし、ｎは正の整数である。）とする。
【００１５】
陽イオン交換性層状化合物に包接する半導体の比率としては、陽イオン交換性層状化合物を100 重量部としたとき、１〜50重量部が好ましく、特に10〜20重量部が好ましい。
【００１６】
【作用】
上述したように、本発明の光分解用触媒は、太陽光によって励起される鉄の酸化物を陽イオン交換性層状化合物に包接してなるので、バルクの酸化鉄に比べてバンドギャップはほとんど上昇せず、太陽光で高い触媒活性を示すことができる。これは超微粒子状の鉄の酸化物などが光励起されて生成される電子が、鉄の酸化物を包接している層状化合物に移動することによって、電荷分離が有効に起こり、電子と正孔の再結合が抑制されるためと思われる。
【００１７】
【実施例】
本発明を以下の具体的実施例によりさらに詳細に説明する。
実施例１
固相法により調製したＫ2 Ｔｉ4 Ｏ9 の粉末を50℃、１Ｎの塩酸水溶液中に１時間分散させ、陽イオン交換性層状化合物Ｈ2 Ｔｉ4 Ｏ9 を得た。これを水溶液に分散させ、イオン交換量でＨ2 Ｔｉ4 Ｏ9 の５倍の量のｎ−Ｃ3 Ｈ7 ＮＨ2 を添加し、50℃で３日間反応させ、層間のＨ+ をオクチルアンモニウムイオンとイオン交換した。
【００１８】
得られた化合物を、［Ｆｅ3 （ＯＣＯＣＨ3 ）7 ＯＨ・２Ｈ2 Ｏ］ＮＯ3 の水溶液（イオン交換すべき量の20倍の［Ｆｅ3 （ＯＣＯＣＨ3 ）7 ＯＨ・２Ｈ2 Ｏ］+ を含有）に懸濁し、50℃で３日間反応させて層間のオクチルアンモニウムイオンと、［Ｆｅ3 （ＯＣＯＣＨ3 ）7 ＯＨ・２Ｈ2 Ｏ］+ とをイオン交換し、［Ｆｅ3 （ＯＣＯＣＨ3 ）7 ＯＨ・２Ｈ2 Ｏ］2 Ｔｉ4 Ｏ9 を得た。得られた化合物を乾燥させた後、濃度０．１Ｎの水酸化ナトリウム水溶液に分散させ、５００Ｗの水銀灯より１０時間紫外線照射し、Ｆｅ2 Ｏ3 を層間に包接した光分解用触媒Ｆｅ2 Ｏ3 ・ｎＨ2 Ｏ／Ｈ2 Ｔｉ4 Ｏ9 を得た。
【００１９】
この光分解用触媒のバンドギャップを測定したところ、２．４ｅＶであり、バルクの酸化鉄のバンドギャップ（２．３ｅＶ）とはほぼ同じである。また、この光分解用触媒を熱重量示差熱分析（ＴＧ−ＤＴＡ）で分析し、［Ｆｅ3 （ＯＣＯＣＨ3 ）7 ＯＨ・２Ｈ2 Ｏ］2 Ｔｉ4 Ｏ9 が残存していないことを確認した。
【００２０】
さらに、Ｆｅ2 Ｏ3 ・ｎＨ2 Ｏ／Ｈ2 Ｔｉ4 Ｏ9 、Ｈ2 Ｔｉ4 Ｏ9 及びＫ2 Ｔｉ4 Ｏ9 を粉末Ｘ線回折分析を行った。結果を図１に示す。図１の（ａ）に示した２θ＝１０．０６１°のピークはＫ2 Ｔｉ4 Ｏ9 の（２００）面の回折である。イオン交換によって生成された（ｂ）Ｈ2 Ｔｉ4 Ｏ9 、（ｃ）Ｆｅ2 Ｏ3 ・ｎＨ2 Ｏ／Ｈ2 Ｔｉ4 Ｏ9 では、このピークが低角度側にシフトしたことから、層間距離が広がったことがわかる。（２００）面の回折ピークより求めた各化合物の層間距離を表１に示す。
【００２１】
表１から明らかなように、Ｆｅ2 Ｏ3 ・ｎＨ2 Ｏ／Ｈ2 Ｔｉ4 Ｏ9 の層間距離がＨ2 Ｔｉ4 Ｏ9 の層間距離より０．２２４ｎｍ増加し、層間に酸化鉄が包接されていることがわかる。なお、ホスト層の厚みが０．３９ｎｍであることから、層間に包接された酸化鉄は厚み０．７４ｎｍの超微粒子であることがわかる。
【００２３】
【発明の効果】
以上詳述したように、本発明の製造方法により得られる光分解用触媒は、太陽光によって励起される鉄の酸化物半導体を、陽イオン交換性層状化合物に包接してなるため、太陽光で高い分解触媒活性を有し、よって効率よく水を光分解したり、二酸化炭素を還元するすることができる。
【図面の簡単な説明】
【図１】 本発明の光分解触媒及びＫ2 Ｔｉ4 Ｏ、Ｈ2 Ｔｉ4 Ｏ9 のＸ線回折分析の結果を示すチャートである。[0001]
[Industrial application fields]
The present invention relates to a method for producing a photolysis catalyst that converts light energy into chemical energy, and more particularly to a method for producing a catalyst that enables efficient photolysis of water or reduction of carbon dioxide by sunlight.
[0002]
[Prior art and problems to be solved by the invention]
In recent years, a method for producing hydrogen by photodegrading water or the like using a semiconductor as an electrode has been found, and a method for converting light energy into chemical energy has been proposed. Thus, TiO 2 , SrTiO 3, CdS, and the like are known as typical semiconductors capable of photolyzing water into hydrogen and oxygen.
[0003]
However, any semiconductor that can completely photolyze water such as TiO 2 and SrTiO 3 into hydrogen and oxygen has a large band gap of 3 eV or more, and there is a problem that sunlight is hardly usable. In order to improve the utilization efficiency of solar energy, a semiconductor having a band gap of less than 3 eV is desired. However, a semiconductor having a small band gap generally has low catalytic activity and is easily dissolved in a solution. There is a disadvantage that it is inferior in stability.
[0004]
Bulk iron oxide (Fe 2 O 3 ) has a small band gap of 2.3 eV, is stable without light dissolution, and has a high utilization efficiency of sunlight of about 17%. However, the bulk type has a small surface area of the catalytic reaction site and low reaction characteristics. In addition, the efforts made so far to achieve ultrafine particles with the aim of improving the reactivity increase the hand gap due to the quantum size effect, change the photocatalytic properties of the semiconductor, and do not lead to improved reaction properties.
[0005]
Accordingly, an object of the present invention is to provide a photodegradation catalyst that works efficiently with sunlight and a method for producing the same, with the hand gap hardly increasing even when ultrafine particles are formed.
[0006]
[Means for Solving the Problems]
As a result of diligent research in view of the above problems, the present inventor disperses a compound containing a metal ion in an aqueous alkaline compound solution after ion-exchanging a salt compound containing a metal ion such as iron and a cation exchange layered compound. The present inventors completed the present invention by discovering that, when ultraviolet rays were irradiated , ultrafine oxide particles could be formed and the hand gap hardly increased.
[0007]
The method of the present invention for producing a photodegradation catalyst by including a metal oxide semiconductor excited by sunlight in a cation exchange layered compound comprises a salt compound containing metal ions, the cation exchange layered compound, After the ion exchange, the compound containing metal ions is dispersed in an aqueous alkaline compound solution and decomposed by irradiating with ultraviolet rays, thereby producing a photolysis catalyst in which a metal oxide is included between the layers. .
[0008]
Hereinafter, the present invention will be described in detail.
[1] Structure of photodecomposition catalyst The photodecomposition catalyst of the present invention comprises a semiconductor (a) excited by sunlight in a cation exchange layered compound.
[0009]
(a) The semiconductor semiconductor is a metal oxide semiconductor excited by visible light such as sunlight, and specifically iron oxide (Fe 2 O 3 ), bismuth oxide (Bi 2 O 3 ), tungsten oxide. For example, iron oxide is preferable. The above semiconductor has a hand gap of 3 eV or less and catalyzes photolysis reaction with sunlight, but its reactivity is low, so the metal oxide is made into ultrafine particles by inclusion between the layers of the ion-exchange layered compound described below. To do.
[0010]
(b) Cation-exchangeable layered compound The cation-exchangeable layered compound may be any cation-exchangeable layered compound as long as it can exchange the cation between the layered lattices with a cation outside the compound. Specifically, H 2 Ti 4 O 9 , H 4 Nb 6 O 17 , HBiNb 2 O 7 , H 2 La 2 Ti 3 O 10, HNb 3 O 8 and the like are preferable, and H 2 Ti 4 O 9 and H 4 Nb 6 O 17 are particularly preferable.
[0011]
The cation exchange layered compound is composed of a powder of K 2 Ti 4 O 9 , K 4 Nb 6 O 17 , KBiNb 2 O 7 , K 2 La 2 Ti 3 O 10 and KNb 3 O 8 in 0.1 to 10N hydrochloric acid or the like. In an acidic aqueous solution for 1 to 150 hours, and K + between the layers is ion-exchanged with H + .
[0012]
[2] Method for Producing Photodecomposition Catalyst The photodecomposition catalyst of the present invention includes the semiconductor described above in a cation exchange layered compound, and a specific production method thereof will be described.
[0013]
(1) Inclusion to cation-exchange layered compounds Layered compounds such as K 2 Ti 4 O 9 , K 4 Nb 6 O 17 , KBiNb 2 O 7 , K 2 La 2 Ti 3 O 10 and KNb 3 O 8 Cation exchange properties such as H 2 Ti 4 O 9 , H 4 Nb 6 O 17 , HBiNb 2 O 7 , H 2 La 2 Ti 3 O 10 and HNb 3 O 8 obtained by dispersing in an aqueous solution such as hydrochloric acid. The layered compound is dispersed in an organic solvent such as n-hexane or water. Next, an alkylamine such as n-C 8 H 17 NH 2 or n-C 3 H 7 NH 2 is added, and the temperature is at least room temperature and below the boiling point of an organic solvent such as n-hexane or water for 1 hour to 1 week. React and ion-exchange H + between the layers with alkylammonium ions.
[0014]
The alkylammonium ion-containing layered compound is suspended in an aqueous solution of a salt compound containing metal ions. Examples of such a salt compound containing a metal ion include Fe 3+ salt compound and [Fe 3 (OCOCH 3 ) 7 OH.2H 2 O] + salt compound in the case of iron. Salt compounds refer to nitrates, sulfates, acetates, chlorides and the like. This suspension is reacted at a temperature of room temperature or higher and lower than the boiling point of the aqueous solution (about 100 ° C.) for 1 hour to 1 week, and the alkylammonium ion between layers and Fe 3+ or [Fe 3 (OCOCH 3 ) 7 OH · 2H 2 O] + is ion exchanged. After separating the compound, in the case of Fe 3+ , it is dispersed in an aqueous alkaline compound such as sodium hydroxide and hydrolyzed, and in the case of [Fe 3 (OCOCH 3 ) 7 OH · 2H 2 O] + Disperse in an aqueous solution of an alkaline compound such as sodium oxide and irradiate with a light source such as a mercury lamp for 0.5 to 24 hours, or add an oxidizing agent such as hydrogen peroxide and react for 0.5 to 24 hours. Then, Fe 3+ or [Fe 3 (OCOCH 3 ) 7 OH.2H 2 O] + between layers is defined as Fe 2 O 3 .nH 2 O (where n is a positive integer).
[0015]
The ratio of the semiconductor included in the cation exchange layered compound is preferably from 1 to 50 parts by weight, particularly preferably from 10 to 20 parts by weight, based on 100 parts by weight of the cation exchange layered compound.
[0016]
[Action]
As described above, the photodecomposition catalyst of the present invention includes an oxide of iron excited by sunlight in a cation exchange layered compound, so that the band gap is almost increased as compared with bulk iron oxide. Without high light, high catalytic activity can be shown by sunlight. This is because electrons generated by photoexcitation of ultrafine iron oxide, etc., move to the layered compound that encloses the iron oxide, so that charge separation takes place effectively. It seems that recombination is suppressed.
[0017]
【Example】
The invention is illustrated in more detail by the following specific examples.
Example 1
The K 2 Ti 4 O 9 powder prepared by the solid phase method was dispersed in a 1N aqueous hydrochloric acid solution at 50 ° C. for 1 hour to obtain a cation exchange layered compound H 2 Ti 4 O 9 . This was dispersed in an aqueous solution, and n-C 3 H 7 NH 2 in an amount 5 times that of H 2 Ti 4 O 9 in terms of ion exchange was added and reacted at 50 ° C. for 3 days. Interlayer H + was converted to octylammonium. Ion exchanged with ions.
[0018]
The obtained compound was dissolved in an aqueous solution of [Fe 3 (OCOCH 3 ) 7 OH · 2H 2 O] NO 3 (20 times the amount to be ion-exchanged [Fe 3 (OCOCH 3 ) 7 OH · 2H 2 O] + And octylammonium ions between the layers and [Fe 3 (OCOCH 3 ) 7 OH · 2H 2 O] + are ion-exchanged to obtain [Fe 3 (OCOCH 3 ) 7 OH · 2H 2 O] 2 Ti 4 O 9 was obtained. The obtained compound was dried, dispersed in a 0.1N aqueous sodium hydroxide solution, irradiated with ultraviolet rays from a 500 W mercury lamp for 10 hours, and the photodecomposition catalyst Fe 2 O enclosing Fe 2 O 3 between the layers. 3 · nH 2 O / H 2 Ti 4 O 9 was obtained.
[0019]
The band gap of this photolysis catalyst was measured and found to be 2.4 eV, which is substantially the same as the band gap (2.3 eV) of bulk iron oxide. Further, this photolysis catalyst was analyzed by thermogravimetric differential thermal analysis (TG-DTA), and it was confirmed that [Fe 3 (OCOCH 3 ) 7 OH · 2H 2 O] 2 Ti 4 O 9 did not remain. .
[0020]
Further, powder X-ray diffraction analysis was performed on Fe 2 O 3 .nH 2 O / H 2 Ti 4 O 9 , H 2 Ti 4 O 9 and K 2 Ti 4 O 9 . The results are shown in FIG. The peak at 2θ = 10.061 ° shown in FIG. 1A is diffraction of the (200) plane of K 2 Ti 4 O 9 . In (b) H 2 Ti 4 O 9 and (c) Fe 2 O 3 .nH 2 O / H 2 Ti 4 O 9 produced by ion exchange, this peak was shifted to the lower angle side. It can be seen that has spread. Table 1 shows the interlayer distance of each compound determined from the diffraction peak of the (200) plane.
[0021]
As is clear from Table 1, the interlayer distance of Fe 2 O 3 .nH 2 O / H 2 Ti 4 O 9 is increased by 0.224 nm from the interlayer distance of H 2 Ti 4 O 9 , and iron oxide is included between the layers. You can see that In addition, since the thickness of a host layer is 0.39 nm, it turns out that the iron oxide enclosed between layers is a ultrafine particle of thickness 0.74 nm.
[0023]
【The invention's effect】
As described above in detail, the photodegradation catalyst obtained by the production method of the present invention includes an iron oxide semiconductor excited by sunlight in a cation exchange layered compound. It has a high decomposition catalytic activity, so that water can be efficiently photodecomposed and carbon dioxide can be reduced.
[Brief description of the drawings]
FIG. 1 is a chart showing the results of X-ray diffraction analysis of the photolysis catalyst of the present invention and K 2 Ti 4 O and H 2 Ti 4 O 9 .
Claims (1)
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP32168194A JP3782835B2 (en) | 1994-11-30 | 1994-11-30 | Method for producing photolysis catalyst |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP32168194A JP3782835B2 (en) | 1994-11-30 | 1994-11-30 | Method for producing photolysis catalyst |
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| JPH08155309A JPH08155309A (en) | 1996-06-18 |
| JP3782835B2 true JP3782835B2 (en) | 2006-06-07 |
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| JP4526619B2 (en) * | 1999-09-21 | 2010-08-18 | 大塚化学株式会社 | Visible light active photocatalyst |
| JP5036443B2 (en) * | 2007-07-31 | 2012-09-26 | 国立大学法人 東京大学 | Photocatalytic material |
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| JPS59112841A (en) * | 1982-12-21 | 1984-06-29 | Toshiba Corp | Catalyst for photochemical reaction |
| JPH0628737B2 (en) * | 1985-09-20 | 1994-04-20 | 株式会社東芝 | Semiconductor photocatalyst |
| JPH061734A (en) * | 1992-06-17 | 1994-01-11 | Advantest Corp | Photochemical conversion of carbon dioxide into organic matter |
| JPH0889799A (en) * | 1994-09-19 | 1996-04-09 | Nikon Corp | photocatalyst |
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