JP4098527B2 - Highly efficient air-nitrogen-fixed composite photocatalyst material composed of titanium oxide / conductive polymer composite with visible light response - Google Patents
Highly efficient air-nitrogen-fixed composite photocatalyst material composed of titanium oxide / conductive polymer composite with visible light response Download PDFInfo
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- JP4098527B2 JP4098527B2 JP2002004161A JP2002004161A JP4098527B2 JP 4098527 B2 JP4098527 B2 JP 4098527B2 JP 2002004161 A JP2002004161 A JP 2002004161A JP 2002004161 A JP2002004161 A JP 2002004161A JP 4098527 B2 JP4098527 B2 JP 4098527B2
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- 239000002131 composite material Substances 0.000 title claims description 37
- 239000000463 material Substances 0.000 title claims description 36
- 239000011941 photocatalyst Substances 0.000 title claims description 34
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 title claims description 24
- OGIDPMRJRNCKJF-UHFFFAOYSA-N titanium oxide Inorganic materials [Ti]=O OGIDPMRJRNCKJF-UHFFFAOYSA-N 0.000 title claims description 24
- 229920001940 conductive polymer Polymers 0.000 title claims description 13
- 230000004298 light response Effects 0.000 title 1
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 66
- 229910001873 dinitrogen Inorganic materials 0.000 claims description 38
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 claims description 36
- 150000003863 ammonium salts Chemical class 0.000 claims description 30
- 238000006552 photochemical reaction Methods 0.000 claims description 18
- 229910021529 ammonia Inorganic materials 0.000 claims description 17
- 150000001450 anions Chemical class 0.000 claims description 14
- 238000005868 electrolysis reaction Methods 0.000 claims description 12
- 230000001590 oxidative effect Effects 0.000 claims description 9
- 230000001699 photocatalysis Effects 0.000 claims description 9
- 230000003100 immobilizing effect Effects 0.000 claims description 8
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 claims description 6
- VLTRZXGMWDSKGL-UHFFFAOYSA-M perchlorate Chemical compound [O-]Cl(=O)(=O)=O VLTRZXGMWDSKGL-UHFFFAOYSA-M 0.000 claims description 6
- 239000010936 titanium Substances 0.000 claims description 6
- 229910052719 titanium Inorganic materials 0.000 claims description 6
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 6
- 239000000178 monomer Substances 0.000 claims description 5
- 239000008151 electrolyte solution Substances 0.000 claims description 4
- 229910052751 metal Inorganic materials 0.000 claims description 4
- 239000002184 metal Substances 0.000 claims description 4
- 238000006116 polymerization reaction Methods 0.000 claims description 4
- 239000002322 conducting polymer Substances 0.000 claims 1
- 239000010408 film Substances 0.000 description 19
- QENGPZGAWFQWCZ-UHFFFAOYSA-N 3-Methylthiophene Chemical compound CC=1C=CSC=1 QENGPZGAWFQWCZ-UHFFFAOYSA-N 0.000 description 16
- 229910052757 nitrogen Inorganic materials 0.000 description 14
- GDDNTTHUKVNJRA-UHFFFAOYSA-N 3-bromo-3,3-difluoroprop-1-ene Chemical compound FC(F)(Br)C=C GDDNTTHUKVNJRA-UHFFFAOYSA-N 0.000 description 13
- 238000000034 method Methods 0.000 description 10
- 239000013078 crystal Substances 0.000 description 8
- KBLZDCFTQSIIOH-UHFFFAOYSA-M tetrabutylazanium;perchlorate Chemical compound [O-]Cl(=O)(=O)=O.CCCC[N+](CCCC)(CCCC)CCCC KBLZDCFTQSIIOH-UHFFFAOYSA-M 0.000 description 7
- YMWUJEATGCHHMB-UHFFFAOYSA-N Dichloromethane Chemical compound ClCCl YMWUJEATGCHHMB-UHFFFAOYSA-N 0.000 description 6
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 6
- 230000000694 effects Effects 0.000 description 5
- 230000003647 oxidation Effects 0.000 description 5
- 238000007254 oxidation reaction Methods 0.000 description 5
- 230000005611 electricity Effects 0.000 description 3
- 150000002500 ions Chemical class 0.000 description 3
- 229910017464 nitrogen compound Inorganic materials 0.000 description 3
- 150000002830 nitrogen compounds Chemical class 0.000 description 3
- 229910052697 platinum Inorganic materials 0.000 description 3
- 150000003839 salts Chemical class 0.000 description 3
- 239000010409 thin film Substances 0.000 description 3
- 229910020366 ClO 4 Inorganic materials 0.000 description 2
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 239000003792 electrolyte Substances 0.000 description 2
- 238000002474 experimental method Methods 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 229920000642 polymer Polymers 0.000 description 2
- QGZKDVFQNNGYKY-UHFFFAOYSA-O Ammonium Chemical compound [NH4+] QGZKDVFQNNGYKY-UHFFFAOYSA-O 0.000 description 1
- 238000009623 Bosch process Methods 0.000 description 1
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 229910001413 alkali metal ion Inorganic materials 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 125000002091 cationic group Chemical group 0.000 description 1
- 150000001768 cations Chemical class 0.000 description 1
- 239000003638 chemical reducing agent Substances 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000001678 irradiating effect Effects 0.000 description 1
- 230000031700 light absorption Effects 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- MHCFAGZWMAWTNR-UHFFFAOYSA-M lithium perchlorate Chemical compound [Li+].[O-]Cl(=O)(=O)=O MHCFAGZWMAWTNR-UHFFFAOYSA-M 0.000 description 1
- 229910001486 lithium perchlorate Inorganic materials 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 125000002524 organometallic group Chemical group 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 125000004430 oxygen atom Chemical group O* 0.000 description 1
- VLTRZXGMWDSKGL-UHFFFAOYSA-N perchloric acid Chemical compound OCl(=O)(=O)=O VLTRZXGMWDSKGL-UHFFFAOYSA-N 0.000 description 1
- 239000003208 petroleum Substances 0.000 description 1
- 238000013032 photocatalytic reaction Methods 0.000 description 1
- 230000000379 polymerizing effect Effects 0.000 description 1
- 238000006722 reduction reaction Methods 0.000 description 1
- 230000004043 responsiveness Effects 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 239000004449 solid propellant Substances 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- DZLFLBLQUQXARW-UHFFFAOYSA-N tetrabutylammonium Chemical compound CCCC[N+](CCCC)(CCCC)CCCC DZLFLBLQUQXARW-UHFFFAOYSA-N 0.000 description 1
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- Compositions Of Macromolecular Compounds (AREA)
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- Catalysts (AREA)
Description
【０００１】
【発明の属する技術分野】
本発明は、光活性能を改善した水分を含む窒素ガスから光化学反応によりアンモニアを生成させる光触媒機能を持つ酸化チタンおよび該酸化チタンの表面に該光化学反応により生成するアンモニアとアンモニウム塩を形成する陰イオンとを存在させた導電性ポリマーを形成し光活性的に接触複合化した窒素ガスをアンモニウム塩として固定化する複合化光触媒材料に関する。
【０００２】
【従来の技術】
地球上の人口が爆発的に増大している現在、生物体内にある１／３の窒素は合成アンモニアから生産される窒素化合物に支えられている。しかしながら、空中窒素から合成アンモニアを生産するハーバー・ボッシュ法は高温高圧を必要とするエネルギー消費型のアンモニア生産プロセスであり、さら、液体窒素と反応させる水素ガスは石油の分解で得られるものを利用している。従って、石油が枯渇する将来において前記生物体内で要求される窒素化合物を支えるためには、ハーバー法などの代替プロセスの開発が急務であり、国際的な課題となっている。
【０００３】
しかるに、Ｎ２の結合エネルギーは９４２ｋＪ／ｍｏｌであり、イオン化ポテンシャルは１５．６ｅＶ（因みに、Ａｒは１５．８ｅＶ）と窒素ガスから前記従来技術の問題点をなくした窒素を固定するプロセスの開発は非常に困難な課題である。このような中で、代替プロセスとしては、空中窒素を有機金属錯体に固定化し、ついで化学還元を行ってアンモニアガスを合成する常温、常圧の方法（Ｇ．Ｌ．Ｌｅｉｇｈ，科学（Ｓｃｉｅｎｃｅ）誌，第２７９巻，５０６−５０７頁，１９９８年参照）と、酸化チタンに光を照射し、その表面で空中窒素をアンモニアガスに変換する方法（文献１：Ｉｎｄｉａｎ Ｊｏｕｒｎａｌ ｏｆ Ｃｈｅｍｉｓｔｒｙ、Ｖｏｌ．３５Ａ、Ｊｕｎｅ １９９６，ｐｐ４４３−４５３、文献２：Ｇ．Ｎ．Ｓｃｈｒａｕｚｅｒ ａｎｄ Ｔ．Ｄ．Ｇｕｔｈ，アメリカ化学会（Ｊｏｕｒｎａｌ ｏｆ ｔｈｅ Ａｍｅｒｉｃａｎ Ｃｈｅｍｉｃａｌ Ｓｏｃｉｅｔｙ）誌，第９９巻２２号，７１８９−７１９３頁，１９７７年）などが提案されている。
【０００４】
また、本発明者らは、光触媒機能を持つ酸化チタンと窒素ガスから光化学反応により生成するアンモニアとアンモニウム塩を形成する陰イオンを存在させた導電性ポリマーとを光活性的に接触複合化した複合化光触媒材料を、水分を含む窒素ガス雰囲気と光化学反応可能に接触する条件下で、該複合化光触媒材料に光照射して該窒素ガスを光化学反応によりアンモニアに変換し、変換されたアンモニアを該陰イオンのアンモニウム塩として固定化する光化学反応に使用する複合化光触媒材料を用いた光化学反応を利用した窒素ガスをアンモニウム塩として固定化する方法を提案している（特開２００１−７２９８５、２００１年３月２１日公開）。しかしながら、上記提案では窒素固定化効率が非常に低く、より効率的な複合化光触媒材料が望まれる。
【０００５】
【発明が解決しようとする課題】
本発明の課題は、光活性能を改善した窒素ガスをアンモニウム塩として固定化する複合化光触媒材料を提供することにある。前記課題を解決するために、高光活性の光触媒材料を検討する中で、チタン金属を酸化する電解電圧の条件およびモノマーを酸化重合する電解電圧条件として特定の条件を選択することにより、窒素ガスをアンモニウム塩として固定化する効率的な複合化光触媒材料が得られることを見出し、前記課題を解決することができた。
【０００６】
【課題を解決するための手段】
本発明は、（１）光触媒機能を持つ酸化チタンと水分を含む窒素ガスから光化学反応により生成するアンモニアとアンモニウム塩を形成する陰イオンを存在させた導電性ポリマーとを光活性的に接触複合化した複合化光触媒材料を、水分を含む窒素ガス雰囲気と光化学反応可能に接触する条件下で、該複合化光触媒材料に光照射して該窒素ガスを光化学反応によりアンモニアに変換し、変換されたアンモニアを該陰イオンのアンモニウム塩として固定化する光化学反応に使用する複合化光触媒材料において、該複合化光触媒材料がチタン金属を０Ｖより大きく１５Ｖ以下の電解電圧において酸化して生成させた光触媒機能を持つ酸化チタンおよび該酸化チタンの表面に少なくとも該カチオンおよびアニオンからなる塩、および該導電性ポリマーを形成するモノマーが存在する電解液中で７０Ｖ±３０Ｖの定電解電圧を印加して該モノマーを電解酸化重合して該陰イオンが存在する膜厚が１μｍ±０．５μｍの範囲である導電性ポリマーの層を形成することにより得られたものであることを特徴とする窒素ガスをアンモニウム塩として固定化する複合化光触媒材料である。
【０００７】
好ましくは、（２）生成アンモニアとアンモニウム塩を形成する陰イオンが過塩素酸イオンＣｌＯ ４− であることを特徴とする前記（１）に記載の窒素ガスをアンモニウム塩として固定化する複合化光触媒材料である。前記アンモニウム塩として固定することにより、窒素ガスを取り扱いやすい固体燃料もしくは固体窒素化合物として固定化することが可能になった。
【０００８】
【本発明の実施の態様】
本発明をより詳細に説明する。
Ａ．本発明の特徴の第１は、図１から理解されるように、金属チタンを０Ｖより大きく１５Ｖ以下の、特に１０Ｖ以下の電解電圧下において酸化することにより固定化効率を格段に改善した酸化チタン膜を見出したことにある。図１は、陽極酸化電位を変えて酸化チタン膜を作製し、その上に定電解電圧の７０Ｖで３−メチルチオフェンを過塩素酸テトラブチルアンモニウム（ＴＢＡＰ）の存在下で酸化重合して過塩素酸イオンＣｌＯ４−を内包したポリ（３−メチルチオフェン）を導電性ポリマーとする導電性膜を形成して複合化した、窒素ガスをアンモニウム塩として固定化する複合化光触媒材料の窒素固定効率を測定した結果を示している。上記実験において、窒素ガス源としては、室温の湿度４０％の空気を用いた。また、光源としては、１２００ルックスの疑似太陽光を用いた。生成した塩、ここでは過塩素酸アンモニウムの収量は、得られた針状過塩素酸アンモニウム結晶を水に溶解し、インドナフトール法を用いて定量測定した結果から算出した。以下の実験では、特にことわらない限りこの実験条件で測定した結果を示す。カチオンのテトラブチルアンモニウムイオンに代えて、アルカリ金属、例えばＬｉのイオンを用いても同様の結果が得られる。窒素ガス中に水分を存在させることは必須である。水分量は光化学反応によるアンモニアの生成量に関連し、化学量論量的には、窒素ガスの３倍モルの水分である。
【０００９】
Ｂ．本発明の特徴の第２は、導電性ポリマー膜の厚さを１μｍ±０．５μｍにすることにより固定化の効率が顕著に改善されることを見出したことである。図２は陽極酸化電位５Ｖで作製した酸化チタン膜の表面に定電解電圧の７０Ｖで３−メチルチオフェンを過塩素酸テトラブチルアンモニウム（ＴＢＡＰ）の存在下で酸化重合して過塩素酸イオンＣｌＯ４−を内包したポリ（３−メチルチオフェン）を導電性ポリマーとする種々の膜厚の導電性膜を光触媒機能を持つ酸化チタン層表面に形成した窒素ガスをアンモニウム塩として固定化する複合化光触媒材料について、窒素固定効率を測定した結果を示す。窒素固定効率の最大値は３．６ｍｍｏｌ／ｍ２であり、その時の窒素固定化速度は２１μｍｏｌｍ−２ｈ−１である。膜厚の制御は、通電電気量と膜厚は比例するから、通電電気量を制御することにより実施し得る。
【００１０】
Ｃ．本発明の特徴の第３は、本発明の窒素ガスをアンモニウム塩として固定化する複合化光触媒材料は、酸化チタン膜の光吸収特性が紫外光領域の光（４００ｎｍ以下）を吸収するだけなのに対し、可視光領域の光により窒素ガスをアンモニウム塩としての固定化することができることである。本発明の窒素固定複合化光触媒材料が光活性を示す波長特性を調べるために、光フィルターを用いて、疑似太陽光を単色光とし、かつ、各波長の光量を３０μＷ／ｃｍ２とし、露光時間５日での過塩素酸アンモニウム収量を測定した。本発明の複合化光触媒材料を用いると、図３に示される結果から、可視光により窒素ガスをアンモニウム塩として固定できることが理解され、太陽光の利用率が高いことが判る。
【００１１】
Ｄ．本発明の導電性ポリマー層を形成する際に電解液中に添加して、電解中にアンモニアをアンモニウム塩として固定する陰イオンを該ポリマー層中に封入できる該陰イオンを含む電解質としては、本発明者らが提案した、前記先願の発明（特開２００１−７２９８５、２００１年３月２１日公開）で使用したものを利用できる。
Ｅ．図４は、本発明の窒素ガスを光化学反応によりアンモニウム塩として固定する原理を示すものである。
【００１２】
【実施例】
ここでは、更に具体的な例を実施例として示すが、これは本発明をより理解し易くするためのものであり、本発明を限定するものではない。
【００１３】
実施例１
脱脂、フツ酸による酸化物除去を行ったチタン板を陽極とし、過塩素酸テトラブチルアンモニウムを０．１モル溶解したジクロロメタン電解液中で白金板を陰極として、白金板に対して＋５Ｖの電解電圧をかけて酸化して、チタン板上に酸化チタン薄膜を形成した。
【００１４】
前記酸化チタン薄膜を陽極とし、過塩素酸テトラブチルアンモニウムを０．１モルと３−メチルチオフェンを０．０８モルを溶解したジクロロメタン溶液を電解液とし、白金板を陰極として白金板に対して＋７０Ｖの定電解電圧をかけて３−メチルチオフェンを酸化重合し前記酸化チタン薄膜上に過塩素酸イオンＣｌＯ４ −を封入したポリ（３−メチルチオフェン）膜を形成した。この時の通電電気量は２００ミリクーロン／ｃｍ２（ｍＣ／ｃｍ２）とした。
【００１５】
酸化チタン膜／過塩素酸イオンを内包するポリ（３−メチルチオフェン）膜からなる複合化光触媒材料が光化学的に窒素ガスを過塩素酸アンモニウム塩として固定化する効果を以下の方法により確認した。（１） 前記作製した複合化光触媒材料を、外部から光照射可能で、窒素ガスの水分を制御できるシールドボックス装置内に配置し、該シールドボックス内の相対湿度を４０％に制御し、該水分を含む窒素ガスと該複合化光触媒材料とを光化学反応可能に接触させ、外部から１２００ルックスの疑似太陽光を照射した。（２） 一定時間露光後、前記複合化光触媒材料上に過塩素酸アンモニウム針状結晶が形成された。該針状結晶を水に溶解し、前記インドナフトール法で前記過塩素酸アンモニウムの収量を測定した。
【００１６】
一週間照射後の過塩素酸アンモニウム生成量の測定結果を、酸化チタン形成の陽極酸化電位と過塩素酸アンモニウム針状結晶の収量の関係を示す図１中に示す。この図１から、１５Ｖ以下、特に１０Ｖ以下で作製した酸化チタンを用いた場合に窒素固定反応の活性が高いことが判る。陽極酸化電位を低くして作製した酸化チタンほど酸素欠陥（化学量論量に対して酸素原子が欠損している部位）が多く観察されることから、その部位が窒素固定反応の活性を高めているものと推測される。
【００１７】
通電量を変えて作製した、換言すれば、膜厚を変えて作成した複合化光触媒材料の、膜厚と過塩素酸アンモニウム針状結晶の収量の関係を図２に示す。図２の膜厚と収量の関係において、特定の膜厚において収率のピークが存在することが判る。これは、薄すぎると光活性に機能する空乏層の形成が充分でなく、厚すぎると空乏層まで光が到達しないことによるものと推測される。膜厚１μｍにおいて最大の過塩素酸アンモニウム針状結晶の収量が達成でき、その時の窒素固定化速度は２１μｍｏｌ・ｍ−２・ｈ−１であった。
図３は最大の過塩素酸アンモニウム針状結晶の収量が達成された空中窒素固定複合光触媒材料の窒素ガスをアンモニウム塩として固定化する際の波長特性を示している。
【００１８】
実施例２
実施例１のＴＢＡＰに代えて過塩素酸リチウムを用いて実施した場合においても、ほぼ同様の結果が得られた。
【００１９】
【発明の効果】
以上述べたように、本発明で確立した窒素ガスをアンモニウム塩として固定化する複合化光触媒材料を作成する方法を採用することにより、可視光応答性、固定化効率を顕著に向上させた、常温常圧において窒素ガスをアンモニウム塩として固定化できる複合化光触媒材料を提供することができた、という優れた作用・効果がもたらされた。
【図面の簡単な説明】
【図１】 酸化チタン形成の陽極酸化電位と過塩素酸アンモニウム針状結晶の収量の相関
【図２】 窒素ガスから光化学反応により生成するアンモニアとアンモニウム塩を形成する陰イオンを存在させた導電性ポリマーの膜厚と過塩素酸アンモニウム針状結晶の収量の相関
【図３】 本発明の窒素ガスをアンモニウム塩として固定化する複合化光触媒材料の波長特性
【図４】 本発明の窒素ガスをアンモニウム塩として固定化する複合化光触媒材料による光窒素固定の原理[0001]
BACKGROUND OF THE INVENTION
The present invention relates to titanium oxide having a photocatalytic function for generating ammonia by photochemical reaction from nitrogen gas containing moisture with improved photoactivity, and an anode that forms ammonia and an ammonium salt formed by the photochemical reaction on the surface of the titanium oxide. The present invention relates to a composite photocatalyst material that forms a conductive polymer in the presence of ions and immobilizes nitrogen gas, which is photoactively contact-complexed, as an ammonium salt.
[0002]
[Prior art]
At the present time when the population on the earth is increasing explosively, 1/3 of nitrogen in living organisms is supported by nitrogen compounds produced from synthetic ammonia. However, the Harbor Bosch process, which produces synthetic ammonia from nitrogen in the air, is an energy-consuming ammonia production process that requires high temperature and pressure, and the hydrogen gas that reacts with liquid nitrogen is obtained from the decomposition of petroleum. is doing. Accordingly, in order to support the nitrogen compounds required in the organism in the future when oil is depleted, the development of alternative processes such as the Harbor method is an urgent task and has become an international issue.
[0003]
However, the bond energy of N 2 is 942 kJ / mol, the ionization potential is 15.6 eV (Ar is 15.8 eV), and the development of a process for fixing nitrogen that eliminates the problems of the prior art from nitrogen gas is This is a very difficult task. Under such circumstances, as an alternative process, air nitrogen is fixed to an organometallic complex, and then chemical reduction is performed to synthesize ammonia gas at room temperature and atmospheric pressure (GL Leigh, Science (Science). 279, 506-507 (1998) and a method of irradiating titanium oxide with light and converting air nitrogen into ammonia gas on the surface thereof (Reference 1: Indian Journal of Chemistry, Vol. 35A, June). 1996, pp 443-453, Reference 2: GN Schrüzer and TD Guth, Journal of the American Chemical Society, Vol. 99, No. 22, pp. 7189-7193, 1977). Proposed.
[0004]
Further, the present inventors have a titanium oxide and a conductive polymer in the presence of anions that form ammonia and an ammonium salt produced by photochemical reaction of nitrogen gas having a photocatalytic function photoactive contact complexed composite The composite photocatalyst material is irradiated with light under the condition that the photocatalytic material is brought into contact with a nitrogen gas atmosphere containing moisture so as to be capable of photochemical reaction, and the nitrogen gas is converted into ammonia by a photochemical reaction. A method of immobilizing nitrogen gas as an ammonium salt using a photochemical reaction using a composite photocatalyst material used for a photochemical reaction to be immobilized as an ammonium salt of an anion has been proposed (Japanese Patent Application Laid-Open No. 2001-72985, 2001). Released on March 21). However, in the above proposal, nitrogen fixing efficiency is very low, and a more efficient composite photocatalyst material is desired.
[0005]
[Problems to be solved by the invention]
The subject of this invention is providing the composite photocatalyst material which fix | immobilizes the nitrogen gas which improved the photoactivity as an ammonium salt. In order to solve the above-mentioned problem, in studying a photocatalytic material with high photoactivity, nitrogen gas is selected by selecting specific conditions as conditions for the electrolysis voltage for oxidizing titanium metal and electrolysis voltage conditions for oxidative polymerization of monomers. It has been found that an efficient composite photocatalyst material that can be immobilized as an ammonium salt can be obtained, and the aforementioned problems have been solved.
[0006]
[Means for Solving the Problems]
The present invention provides (1) a photoactive contact composite of a conductive polymer in the presence of anions that form ammonia and an ammonium salt produced by photochemical reaction of nitrogen gas containing titanium oxide and water having a photocatalytic function The composite photocatalyst material is irradiated with light in a nitrogen gas atmosphere containing moisture so as to be capable of photochemical reaction. The composite photocatalyst material is irradiated with light to convert the nitrogen gas into ammonia by a photochemical reaction. In the composite photocatalyst material used for the photochemical reaction in which is immobilized as the ammonium salt of the anion, the composite photocatalyst material has a photocatalytic function formed by oxidizing titanium metal at an electrolysis voltage of more than 0V and not more than 15V. Titanium oxide and a salt comprising at least the cation and anion on the surface of the titanium oxide, and the conductive polymer Conductivity whose thickness is in the range of 1 μm ± 0.5 μm by applying a constant electrolysis voltage of 70V ± 30V in the electrolytic solution in which the monomer forming the electrolysis is applied and electrolytically oxidizing and polymerizing the monomer. It is a composite photocatalyst material for immobilizing nitrogen gas as an ammonium salt, which is obtained by forming a layer of a conductive polymer.
[0007]
Preferably, (2) the composite photocatalyst for immobilizing nitrogen gas as ammonium salt according to (1) above, wherein the anion that forms ammonium salt with the produced ammonia is perchlorate ion ClO 4− Material. By fixing as the ammonium salt, nitrogen gas can be fixed as a solid fuel or a solid nitrogen compound that is easy to handle.
[0008]
[Embodiments of the present invention]
The present invention will be described in more detail.
A. The first feature of the present invention is that, as can be understood from FIG. 1, titanium oxide having a markedly improved immobilization efficiency by oxidizing metal titanium under an electrolysis voltage of more than 0V and not more than 15V, particularly not more than 10V. It is in finding a film. In FIG. 1, a titanium oxide film is produced by changing the anodic oxidation potential, and 3-methylthiophene is oxidized and polymerized in the presence of tetrabutylammonium perchlorate (TBAP) at a constant electrolysis voltage of 70V. Nitrogen fixing efficiency of a composite photocatalyst material that fixes and combines nitrogen gas as an ammonium salt formed by forming a conductive film using poly (3-methylthiophene) encapsulating acid ion ClO 4- as a conductive polymer. The measurement results are shown. In the above experiments, air having a humidity of 40% at room temperature was used as the nitrogen gas source. As a light source, 1200-lux pseudo-sunlight was used. The yield of the produced salt, here ammonium perchlorate, was calculated from the results obtained by dissolving the obtained needle-like ammonium perchlorate crystal in water and quantitatively measuring it using the indonaphthol method. In the following experiments, unless otherwise stated, the results measured under these experimental conditions are shown. Similar results can be obtained by using an alkali metal ion such as Li instead of the cationic tetrabutylammonium ion. It is essential that moisture be present in the nitrogen gas. The amount of water is related to the amount of ammonia produced by the photochemical reaction, and stoichiometrically is three times the amount of water as nitrogen gas.
[0009]
B. The second feature of the present invention is that it has been found that the immobilization efficiency is remarkably improved by setting the thickness of the conductive polymer film to 1 μm ± 0.5 μm. Figure 2 is anodic oxidation potential 5V of 3-methylthiophene in 70V constant electrolysis voltage to the surface of the titanium oxide film produced in by oxidative polymerization in the presence of tetrabutylammonium perchlorate (TBAP) perchlorate ion ClO 4 - composite photocatalyst material for immobilizing nitrogen gas formed in the titanium oxide layer surface as the ammonium salt having a photocatalytic function of various thicknesses of the conductive film to encapsulated poly (3-methylthiophene) was the electrically conductive polymer Shows the results of measuring the nitrogen fixation efficiency. The maximum value of nitrogen fixation efficiency is 3.6 mmol / m 2 , and the nitrogen fixation rate at that time is 21 μmol −2 h −1 . The film thickness can be controlled by controlling the amount of energized electricity because the amount of energized electricity is proportional to the film thickness.
[0010]
C. The third feature of the present invention is that the composite photocatalyst material in which the nitrogen gas of the present invention is immobilized as an ammonium salt only absorbs light in the ultraviolet region (400 nm or less) in light absorption characteristics of the titanium oxide film. The nitrogen gas can be immobilized as an ammonium salt by light in the visible light region. In order to investigate the wavelength characteristic that the nitrogen-fixed composite photocatalyst material of the present invention exhibits photoactivity, pseudo-sunlight is set to monochromatic light using an optical filter, the light quantity of each wavelength is set to 30 μW / cm 2 , and the exposure time The yield of ammonium perchlorate at 5 days was measured. When the composite photocatalyst material of the present invention is used, it is understood from the results shown in FIG. 3 that nitrogen gas can be fixed as an ammonium salt by visible light, and the utilization rate of sunlight is high.
[0011]
D. An electrolyte containing the anion that can be added to the electrolyte when forming the conductive polymer layer of the present invention and can fix the anion that fixes ammonia as an ammonium salt during electrolysis in the polymer layer is The ones used in the invention of the prior application proposed by the inventors (Japanese Patent Laid-Open No. 2001-72985, published on March 21, 2001) can be used.
E. Figure 4 shows the principle of securing the nitrogen gas of the present invention as by Ri ammonium salt photochemical reaction.
[0012]
【Example】
Here, more specific examples will be shown as examples, but this is intended to make the present invention easier to understand, and does not limit the present invention.
[0013]
Example 1
A titanium plate that has been degreased and oxide removed with hydrofluoric acid is used as an anode, and a platinum plate is used as a cathode in a dichloromethane electrolyte solution containing 0.1 mol of tetrabutylammonium perchlorate. Was oxidized to form a titanium oxide thin film on the titanium plate.
[0014]
The titanium oxide thin film is used as an anode, a dichloromethane solution in which 0.1 mol of tetrabutylammonium perchlorate and 0.08 mol of 3-methylthiophene are dissolved is used as an electrolytic solution, and a platinum plate is used as a cathode and +70 V with respect to the platinum plate. constant electrolysis voltage over 3-methylthiophene was oxidative polymerization perchlorate on the titanium oxide thin film ion ClO 4 - to form a sealed poly (3-methylthiophene) film. The amount of electricity applied at this time was 200 millicoulombs / cm 2 (mC / cm 2 ).
[0015]
The effect of photochemically immobilizing nitrogen gas as ammonium perchlorate was confirmed by the following method using a composite photocatalyst material composed of a titanium oxide film / poly (3-methylthiophene) film containing perchlorate ions. (1) The composite photocatalyst material produced is placed in a shield box device that can be irradiated with light from the outside and can control the moisture of nitrogen gas, and the relative humidity in the shield box is controlled to 40%. The composite photocatalyst material was brought into contact with the nitrogen gas containing the photocatalytic reaction, and was irradiated with pseudo-sunlight of 1200 lux from the outside. (2) After exposure for a certain time, ammonium perchlorate needle-like crystals were formed on the composite photocatalyst material. The acicular crystals were dissolved in water, and the yield of the ammonium perchlorate was measured by the indonaphthol method.
[0016]
The measurement results of the amount of ammonium perchlorate produced after one week of irradiation are shown in FIG. 1 showing the relationship between the anodic oxidation potential of titanium oxide formation and the yield of ammonium perchlorate needle crystals. From FIG. 1, it can be seen that the activity of nitrogen fixation reaction is high when titanium oxide prepared at 15 V or less, particularly 10 V or less is used. Titanium oxide produced with a lower anodic oxidation potential has more oxygen defects (sites where oxygen atoms are missing relative to the stoichiometric amount), which increases the activity of the nitrogen fixation reaction. Presumed to be.
[0017]
FIG. 2 shows the relationship between the film thickness and the yield of needle-shaped ammonium perchlorate crystals of a composite photocatalyst material prepared by changing the energization amount, in other words, by changing the film thickness. From the relationship between the film thickness and the yield in FIG. 2, it can be seen that there is a yield peak at a specific film thickness. This is presumably due to the fact that if the film is too thin, the depletion layer that functions to photoactivity is not sufficiently formed, and if it is too thick, the light does not reach the depletion layer. When the film thickness was 1 μm, the maximum yield of ammonium perchlorate needle crystals could be achieved, and the nitrogen fixation rate at that time was 21 μmol · m −2 · h −1 .
FIG. 3 shows wavelength characteristics when nitrogen gas is immobilized as an ammonium salt of an air-nitrogen-fixed composite photocatalyst material in which the maximum yield of ammonium perchlorate needles is achieved .
[0018]
Example 2
In the case where lithium perchlorate was used instead of TBAP in Example 1, substantially the same results were obtained.
[0019]
【The invention's effect】
As described above, by adopting a method of creating a composite photocatalyst material that immobilizes nitrogen gas as an ammonium salt established in the present invention, visible light responsiveness and immobilization efficiency are remarkably improved. An excellent action and effect was achieved that a composite photocatalyst material capable of fixing nitrogen gas as an ammonium salt at normal pressure could be provided.
[Brief description of the drawings]
Fig. 1 Correlation between anodic oxidation potential of titanium oxide formation and yield of ammonium perchlorate needle-like crystals Fig. 2 Conductivity in the presence of ammonia and anion forming ammonium salt by photochemical reaction from nitrogen gas Correlation between film thickness of polymer and yield of ammonium perchlorate needle crystal [Fig. 3] Wavelength characteristics of composite photocatalyst material immobilizing nitrogen gas of the present invention as ammonium salt [Fig. 4] Nitrogen gas of the present invention to ammonium Principle of photonitrogen fixation by composite photocatalyst material immobilized as salt
Claims (2)
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| JP4576526B2 (en) * | 2004-07-07 | 2010-11-10 | 国立大学法人京都大学 | Ultraviolet and visible light responsive titania photocatalyst |
| WO2007097220A1 (en) * | 2006-02-21 | 2007-08-30 | Kyoto University | Visible light-responsive photocatalyst |
| JP5401666B2 (en) * | 2007-03-08 | 2014-01-29 | 国立大学法人 千葉大学 | Nitrogen fixing material, method for producing the same, and nitrogen fixing method |
| JP5604204B2 (en) * | 2010-07-21 | 2014-10-08 | 日立造船株式会社 | Ammonia synthesis method |
| JP5725530B2 (en) * | 2010-09-03 | 2015-05-27 | 国立大学法人 千葉大学 | Nitrogen immobilization material and nitrogen immobilization method using the same |
| JP2014151291A (en) * | 2013-02-12 | 2014-08-25 | Denso Corp | Ammonia-producing catalyst |
| JP2015120118A (en) | 2013-12-24 | 2015-07-02 | 株式会社デンソー | Ammonia synthesis catalyst |
| CN114749115B (en) * | 2022-03-24 | 2023-06-30 | 福州大学 | Method for gas-phase photocatalytic nitrogen fixation reaction |
| CN114849726A (en) * | 2022-06-23 | 2022-08-05 | 杭州师范大学 | Iron-tungsten oxide photocatalyst with rich oxygen vacancies, preparation and nitrogen fixation application |
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