JP4082800B2 - Catalyst production method - Google Patents
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- JP4082800B2 JP4082800B2 JP27737798A JP27737798A JP4082800B2 JP 4082800 B2 JP4082800 B2 JP 4082800B2 JP 27737798 A JP27737798 A JP 27737798A JP 27737798 A JP27737798 A JP 27737798A JP 4082800 B2 JP4082800 B2 JP 4082800B2
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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
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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
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
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Description
【０００１】
【発明の属する分野】
本発明は、燃料電池用電極として適した触媒の製造方法に関し、さらに詳しくは、量産性に優れそして白金粒子を均一且つ高分散性で担持することのできる触媒の製造方法に関する。
【０００２】
【従来の技術】
燃料電池用白金触媒においては電極触媒の活性を高めることが必要であって、触媒の活性は白金粒子を微細化して担体上に均一に分散させることにより高めることができる。
【０００３】
白金触媒の担持方法としては、従来から多数の方法が知られており、例えば、カーボン粉末に塩化白金酸溶液を含浸し、これにヒドラジン、水素化ホウ素ナトリウム等の還元剤を加え、塩化白金酸を還元して白金を担体表面に析出させる方法が知られている。この湿式還元法では、還元により生成する白金粒子が凝集し粒子径が大きくなってしまい触媒活性が低下するため、界面活性剤等を加えて白金粒子の凝集を抑制することが提案されている。しかしながら、界面活性剤を添加しても、白金粒子の凝集を十分に阻止することができず、更に界面活性剤を除去するための工数が増えるという問題がある。
【０００４】
このため、本発明者らは、先に、疎水化処理したカーボンシートに式
[Pt(NH3)x(NO2)yL]Az
式中、
Ｌはアルコキシ基、アルカノイル基又はアルカノイルオキシ基を表し、
ＡはＨ、ＮＯ2又はＮＯ3を表し、
ｘは０、１又は２であり、ｙは１、２又は３であり、ただし、ｘとｙの合計は中心白金の電荷によって変わり３〜５であり、
ｚは中心金属の電荷によって変わり(ｙ−１)〜(ｙ−３)である、
で示される白金アンミン系錯体を溶存種として含有するアルコール溶液を含浸させた後、水素ガス雰囲気下で加熱還元し、白金の微粒子を該カーボンシート上に析出、担持させる方法を提案した（特開平８−１６２１２２号公報参照）。
【０００５】
しかし、担体として疎水化処理したカーボンシートの代りにカーボン粉末を使用し、上記と同様に白金アンミン系錯体のアルコール溶液を含浸後、水素ガス雰囲気下で加熱還元した場合、例えば３０ｗｔ％Ｐｔ／Ｃ以上となるような白金の担持では白金粒子の凝集が起こることがあり、必ずしも満足できるものではなかった。また、水素ガス雰囲気下では急激に還元反応が起るため、通常は水素ガスを不活性ガスで希釈した混合ガス気流中で行われるが、それでも還元量を多くすると還元反応熱に伴い還元反応が制御できなくなる場合があり、量産ができないという問題がある。
【０００６】
【発明が解決しようとする課題】
本発明の目的は上記の如き課題を解決し、カーボン粉末上に高分散で微細な白金粒子を担持することができ、また量産性に優れた触媒の製造方法を提供することである。
【０００７】
【課題を解決するための手段】
本発明は式
[Pt(NH3)x(NO2)yL]Az (1)
式中、
Ｌはアルコキシ基、アルカノイル基又はアルカノイルオキシ基を表し、
ＡはＨ、ＮＯ2又はＮＯ3を表し、
ｘは０、１又は２であり、ｙは１、２又は３であり、ただし、ｘとｙの合計は中心白金の電荷によって変わり３〜５であり、
ｚは中心金属の電荷によって変わり(ｙ−１)〜(ｙ−３)である、
で示される白金アンミン系錯体を溶存種として含有するアルコール溶液中にカーボン粉末を浸漬し、該溶液を６０℃以上の温度に加熱してカーボン粉末上に白金を析出させることを特徴とする白金担持触媒の製造方法を提供するものである。
【０００８】
【発明の実施の形態】
以下、本発明の方法について更に詳細に説明する。
【０００９】
本発明の方法において使用される前記式（１）の白金アンミン系錯体は、例えば、２価のジニトロジアンミン白金塩を硝酸で処理し、得られるトリニトロジアンミン白金塩をアルコールと反応させることによって製造することができる。
【００１０】
原料として用いられる２価のジニトロジアンミン白金塩は、それ自体概知の化合物であり、例えば白金を王水溶解し、その後脱硝を行い塩化白金酸水溶液とした後、亜硝酸を加え煮沸して亜硝酸白金溶液を得、次いでこの溶液にアンモニア水を加え反応させることにより製造することができる。また、２価のジニトロジアンミン白金塩は平面４配位錯体であり、シス型及びトランス型の形態を持つが、式（１）の白金ニトロアンミン系錯体を製造するに当たっては、いずれの形態の錯体を用いてもよくあるいはその混合物を用いてもよく、いかなる市販品を用いることも可能である。
【００１１】
このようにして得られる２価のジニトロジアンミン白金塩は硝酸水溶液、通常濃度が２００〜７００ｇ・ｄｍ-3の硝酸水溶液中に６０〜１１２℃において溶解し、約３〜１６時間維持することにより、４価の白金錯体、例えばトリニトロジアンミン白金塩を生成させることができる。より具体的には、白金換算で３５０〜６００ｇ・ｄｍ-3のジニトロジアンミン白金塩を硝酸濃度が４５０〜７００ｇ・ｄｍ-3の硝酸水溶液に溶解し、該溶液を常圧で１０７℃以上の煮沸条件下に３〜６時間維持することにより、４価の白金錯体を得ることができる。この４価の白金錯体の生成は、ＪＩＳ−Ｋ８１５３に記載の方法に従い、JIS特級試薬に該当する塩化白金酸６水和物の吸光度と対比することにより確認することができ、その生成量は、通常、塩化白金酸６水和物の吸光度を１００とした相対吸光度で９２〜９４％程度である。
【００１２】
前記式（１）の白金アンミン系錯体は、得られるトリニトロジアンミン白金塩をアルコールと反応させることにより得ることができる。この反応はトリニトロジアンミン白金塩にアルコールを徐々に加え、約２０〜約５０℃の温度に保持しながら行うことができる。またトリニトロジアンミン白金塩として溶液状のものを用いる場合、溶液中の白金メタル濃度が２５０ｇ・ｄｍ-3以上のものを使用するのが好ましく、更にロータリーエバポレータを使用して、加熱乾固を行ない粉末状としたものを使用するのがより好ましい。一方、アルコールの使用量は厳密に制限されるものではないが、通常、４価の白金錯体中の白金重量に基づいて０．５〜２０倍、好ましくは２〜１５倍の重量で用いるのが適当である。
【００１３】
この反応において、４価の白金錯体中の白金イオンがアルコールにより還元され、それと同時にアルコールは反応条件に依存してその少なくとも一部はアルデヒド及び／又はカルボン酸に変化し、これらはそれぞれアルコキシ基、アルカノイル基、アルカノイルオキシ基として錯体中に導入される。ここでアルコールとしては、例えば、メタノール、エタノール、プロパノール、イソプロパノール、ブタノール等の低級アルコール等が挙げられ、中でもエタノールが好適である。
【００１４】
前記式（１）の白金アンミン系錯体の具体例としては、例えばその製造の際の溶媒としてエタノールを用いた場合、次のものが挙げられる。
【００１５】
Pt(IV)(NH3)2(NO2)3(OC2H5)
Pt(IV)(NO2)3(OC2H5)
Pt(IV)(NH3)2(NO2)2(OC2H5)(NO3)
Pt(II)(NH3)(NO2)(OC2H5)
[Pt(II) (NH3)(NO2)2(OC2H5)]H
[Pt(II) (NO2)3(OC2H5)]H2
Pt(IV) (NH3)2(NO2)3(COCH3)
Pt(II) (NH3)2(NO2)(COCH3)
[Pt(II) (NH3)(NO2)2(COCH3)]H
Pt(IV) (NH3)2(NO2)3(OCOCH3)
Pt(II) (NH3)2(NO2)(OCOCH3)
[Pt(II) (NH3)(NO2)2(OCOCH3)]H など。
【００１６】
以上に述べた如くして製造される前記式（１）の白金アンミン系錯体は、アルコール又はアルコール水溶液で希釈し、白金アンミン系錯体のアルコール溶液からなる担持溶液とする。該担持溶液中の白金メタル量は、一般に、１〜４０ｇ・ｄｍ-3の範囲内とすることができ、特に２〜３０ｇ・ｄｍ-3の範囲内が好ましい。また、アルコール水溶液を使用して白金アンミン系錯体のアルコール溶液を得る場合の該水溶液中のアルコール濃度は、通常、２０ｗｔ％以上、好ましくは３０ｗｔ％以上とすることができる。
【００１７】
上記のようして調製される担持溶液にカーボン粉末を浸漬する。この浸漬処理に使用される担持溶液量はカーボン粉末が完全に浸る量以上であればよく、また、カーボン粉末は市販品をそのまま使用することができるが、一般には、それ自体既知の方法（例えば、硝酸等）による親水化処理を予め施したほうがより好ましい。カーボン粉末を浸漬した担持溶液は、例えば超音波ホモジナイザーで約５分間混合した後、該混合液を還流装置付の容器に入れ、６０℃以上、好ましくは６４℃以上の温度で還元を行う。還元温度が６０℃より低い場合には還元に長い時間を要し不経済である。また、還元温度の上限は特に限定されるものではないが、通常は使用するアルコールの沸点以下とするのが好ましい。還元時間は使用するアコルコール及び還元温度に依存するが、通常、約２〜約６時間とすることができる。還元処理終了後、濾過洗浄し、次いで乾燥することにより、白金が高分散で担持された白金担持カーボン粉末触媒を得ることができる。
【００１８】
【実施例】
以下、実施例により本発明をさらに具体的に説明するが、本発明はこれら実施例のみに限定されるものではない。
実施例１
白金換算で50gのジニトロジアンミン白金塩を硝酸濃度500ｇ・ｄｍ-3の溶液100mLに添加し、109℃にて5時間混合攪拌し、ジニトロジアンミン白金塩を溶解、熟成したトリニトロジアンミン白金の硝酸溶液を得た。次に80℃のロータリーエバポレーターで蒸発乾固させて黄茶色粉末を得た。この粉末にエタノールを50℃以下に保持しながら徐々に加えて白金濃度50ｇ・ｄｍ-3の白金アンミンエトキシド錯体溶液を調製した。この白金アンミンエトキシド錯体溶液80mLにエタノール720mLを加えて橙赤色の担持溶液を得た。
【００１９】
この担持溶液に60%硝酸水溶液で親水化処理したカーボン粉末「バルカンXC-72R」（Cabot社製）6.0gを加えて超音波ホモジナイザーで混合した。その後、該担持溶液をロータリーエバポレーターにて、78℃で3時間加熱し還元した。ついでこの反応溶液を濾過し、蒸留水で洗浄後、乾燥してカーボン担持白金触媒を得た。なお、濾過後の溶液は無色透明であった。
実施例２
実施例1と同様にしてトリニトロジアンミン白金の硝酸溶液を得た後、この溶液にエタノールを50℃以下の保持しながら徐々に加えて白金濃度50ｇ・ｄｍ-3白金アンミンエトキシド錯体溶液を調製した。この白金アンミンエトキシド錯体溶液80mLにエタノール720mLを加えて橙赤色の担持溶液を得た。この担持溶液に実施例1と同じカーボン粉末6.0ｇを加えて超音波ホモジナイザーで混合した。その後、該担持溶液をロータリーエバポレーターにて、78℃で3時間加熱し還元した。この反応溶液を濾過し、蒸留水で洗浄後、乾燥してカーボン担持白金触媒を得た。なお、濾過後の溶液は無色透明であった。
実施例３
実施例1と同様にして得られた白金アンミンエトキシド錯体溶液80mLに50%エタノール水溶液720mLを加えて橙赤色の担持溶液を得た。この担持溶液に実施例1と同じカーボン粉末6.0ｇを加えて超音波ホモジナイザーで混合した。その後、該担持溶液をロータリーエバポレーターにて、78℃で3時間加熱し還元した。この反応溶液を濾過し、蒸留水で洗浄後、乾燥してカーボン担持白金触媒を得た。なお、濾過後の溶液は無色透明であった。
比較例１
実施例１の担持溶液に実施例1と同じカーボン粉末6.0ｇを加えて超音波ホモジナイザーで混合した。その後、該担持溶液をロータリーエバポレーターにて、50℃で16時間加熱し還元した。この反応溶液を濾過し、蒸留水で洗浄後、乾燥してカーボン担持白金触媒を得た。なお、濾過後の溶液は橙白色であった。
比較例２
実施例1で得られた白金アンミンエトキシド錯体溶液80mLに蒸留水720mLを加えて橙赤色の担持溶液を得た。この担持溶液に実施例1と同じカーボン粉末6.0ｇを加えて超音波ホモジナイザーで混合した。その後、該担持溶液をロータリーエバポレーターにて、78℃で3時間加熱し還元した。この反応溶液を濾過し、蒸留水で洗浄後、乾燥してカーボン担持白金触媒を得た。なお、濾過後の溶液は黄白色であった。
比較例３
実施例1の担持溶液に実施例1と同じカーボン粉末6.0ｇと凝集防止剤ポリビニルアルコール5.0gを加えて超音波ホモジナイザーで混合した。2.0%水素化ホウ素ナトリウム水溶液100ｍＬを徐々に加えていき3時間攪拌しながら還元した。この反応溶液を50%エタノール水溶液で5回デカンテーション行い濾過し、蒸留水で洗浄後、乾燥してカーボン担持白金触媒を得た。
比較例４
実施例1の担持溶液に実施例1と同じカーボン粉末6.0ｇを加えて超音波ホモジナイザーで混合し、24時間真空乾燥する。その該乾燥カーボン粉末を窒素雰囲気で80℃に昇温し、ついで5%水素‐窒素気流下として20時間加熱処理を行ない還元しカーボン担持白金触媒を得た。しかし、還元開始直後30分程度は還元反応熱により110℃に昇温し温度制御ができなかった。
比較例５
市販の白金濃度50ｇ・ｄｍ-3のジニトロジアンミン白金硝酸水溶液80mLにエタノール720mLを加えて赤褐色の担持溶液を得た。この担持溶液に実施例1と同じカーボン粉末6.0ｇを加えて超音波ホモジナイザーで混合した。その後、該担持溶液をロータリーエバポレーターにて、78℃で18時間加熱し還元した。この反応溶液を濾過し、蒸留水で洗浄後、乾燥してカーボン担持白金触媒を得た。なお、濾過後の溶液は黄白色であった。
【００２０】
上記実施例及び比較例の担持溶液の白金量とカーボン粉末に担持した白金量とを求め、下記式より白金担持率（％）を算出した。その結果を表-1に示す。
【００２１】
【数１】
【００２２】
表-1の結果から明らかなように、実施例1〜3の触媒は、白金担持率が極めて高く、カーボンに担持した白金の結晶子径が小さいことがわかる。
【００２３】
【表１】
【００２４】
さらに、実施例1及び比較例4のカーボン担持白金触媒を使って作製した電極を、プロトン導電性高分子電解質膜ナフィオン１１２（デュポン社製）の両面に接合し、燃料電池としての性能を測定した。その結果を図1に示す。図1の結果から明らかなように、実施例のカーボン担持触媒は高活性で電池性能は向上している。
【００２５】
【発明の効果】
以上述べたとおり、本発明の方法によれば、白金を結晶子径が小さく、高分散で担持させることができ、さらに、還元操作時間も短くまた還元性ガスを使用する必要がないので、量産性及び作業性の優れた触媒の製造方法が提供することができる。
【図面の簡単な説明】
【図１】実施例１及び比較例４のカーボン担持白金触媒を使って作製した燃料電池の性能を測定した結果を示すグラフである。[0001]
[Field of the Invention]
The present invention relates to a method for producing a catalyst suitable as an electrode for a fuel cell, and more particularly to a method for producing a catalyst which is excellent in mass productivity and can carry platinum particles uniformly and with high dispersibility.
[0002]
[Prior art]
In the platinum catalyst for fuel cells, it is necessary to increase the activity of the electrode catalyst, and the activity of the catalyst can be increased by making the platinum particles finely dispersed uniformly on the support.
[0003]
As a method for supporting a platinum catalyst, many methods have been conventionally known. For example, carbon powder is impregnated with a chloroplatinic acid solution, and a reducing agent such as hydrazine or sodium borohydride is added thereto. A method is known in which platinum is reduced and platinum is deposited on the surface of the support. In this wet reduction method, platinum particles produced by the reduction aggregate to increase the particle diameter and reduce the catalytic activity. Therefore, it has been proposed to add a surfactant or the like to suppress aggregation of the platinum particles. However, even if a surfactant is added, aggregation of platinum particles cannot be sufficiently prevented, and there is a problem that the number of steps for removing the surfactant increases.
[0004]
For this reason, the present inventors have previously applied a formula to the hydrophobized carbon sheet.
[Pt (NH 3 ) x (NO 2 ) yL] Az
Where
L represents an alkoxy group, an alkanoyl group or an alkanoyloxy group,
A represents H, NO2 or NO3,
x is 0, 1 or 2, and y is 1, 2 or 3, provided that the sum of x and y varies from 3 to 5 depending on the charge of the central platinum,
z varies depending on the charge of the central metal and is (y-1) to (y-3).
A method of impregnating an alcohol solution containing a platinum ammine complex represented by formula (1) as a dissolved species and then heating and reducing in a hydrogen gas atmosphere to deposit and support platinum fine particles on the carbon sheet was proposed (Japanese Patent Application Laid-Open (JP-A)). No. 8-162122).
[0005]
However, when carbon powder is used in place of the carbon sheet hydrophobized as a carrier and impregnated with an alcohol solution of a platinum ammine complex in the same manner as described above, and heated and reduced in a hydrogen gas atmosphere, for example, 30 wt% Pt / C The platinum loading as described above may cause aggregation of platinum particles, which is not always satisfactory. In addition, since a reduction reaction occurs rapidly in a hydrogen gas atmosphere, it is usually performed in a mixed gas stream in which hydrogen gas is diluted with an inert gas. However, if the reduction amount is increased, the reduction reaction occurs with the heat of the reduction reaction. There is a problem that it may become impossible to control and mass production is not possible.
[0006]
[Problems to be solved by the invention]
An object of the present invention is to solve the above-described problems, and to provide a catalyst production method that can support highly dispersed fine platinum particles on carbon powder and is excellent in mass productivity.
[0007]
[Means for Solving the Problems]
The present invention is a formula
[Pt (NH 3 ) x (NO 2 ) yL] Az (1)
Where
L represents an alkoxy group, an alkanoyl group or an alkanoyloxy group,
A represents H, NO2 or NO3,
x is 0, 1 or 2, and y is 1, 2 or 3, provided that the sum of x and y varies from 3 to 5 depending on the charge of the central platinum,
z varies depending on the charge of the central metal and is (y-1) to (y-3).
A platinum support characterized in that carbon powder is immersed in an alcohol solution containing a platinum ammine complex as a dissolved species, and the solution is heated to a temperature of 60 ° C. or higher to deposit platinum on the carbon powder. A method for producing a catalyst is provided.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the method of the present invention will be described in more detail.
[0009]
The platinum ammine complex of the above formula (1) used in the method of the present invention is produced, for example, by treating a divalent dinitrodiammine platinum salt with nitric acid and reacting the resulting trinitrodiammine platinum salt with an alcohol. can do.
[0010]
The divalent dinitrodiammine platinum salt used as a raw material is a compound known per se. For example, platinum is dissolved in aqua regia and then denitrated to form a chloroplatinic acid aqueous solution. It can be produced by obtaining a platinum nitrate solution and then reacting this solution with aqueous ammonia. In addition, the divalent dinitrodiammine platinum salt is a planar four-coordinate complex and has cis-type and trans-type forms. In producing the platinum nitroammine complex of the formula (1), any form of complex May be used, or a mixture thereof may be used, and any commercially available product may be used.
[0011]
The divalent dinitrodiammine platinum salt thus obtained is dissolved in a nitric acid aqueous solution, usually in a nitric acid aqueous solution having a concentration of 200 to 700 g · dm −3 at 60 to 112 ° C. and maintained for about 3 to 16 hours, Tetravalent platinum complexes such as trinitrodiammine platinum salts can be produced. More specifically, 350 to 600 g · dm −3 of dinitrodiammine platinum salt in terms of platinum is dissolved in an aqueous nitric acid solution having a nitric acid concentration of 450 to 700 g · dm −3, and the solution is boiled at 107 ° C. or higher at normal pressure. By maintaining for 3 to 6 hours under conditions, a tetravalent platinum complex can be obtained. The formation of this tetravalent platinum complex can be confirmed by comparing with the absorbance of chloroplatinic acid hexahydrate corresponding to the JIS special grade reagent according to the method described in JIS-K8153. Usually, the relative absorbance is about 92 to 94% with the absorbance of chloroplatinic acid hexahydrate being 100.
[0012]
The platinum ammine complex of formula (1) can be obtained by reacting the obtained trinitrodiammine platinum salt with an alcohol. This reaction can be carried out while gradually adding alcohol to the trinitrodiammine platinum salt and maintaining the temperature at about 20 to about 50 ° C. In addition, when using a solution in the form of a trinitrodiammine platinum salt, it is preferable to use a platinum metal concentration in the solution of 250 g · dm −3 or more, and further heat to dryness using a rotary evaporator. It is more preferable to use a powder. On the other hand, the amount of alcohol used is not strictly limited, but is usually 0.5 to 20 times, preferably 2 to 15 times based on the weight of platinum in the tetravalent platinum complex. Is appropriate.
[0013]
In this reaction, platinum ions in the tetravalent platinum complex are reduced by the alcohol, and at the same time, depending on the reaction conditions, at least a part of the alcohol is converted to an aldehyde and / or carboxylic acid, which are each an alkoxy group, An alkanoyl group and an alkanoyloxy group are introduced into the complex. Here, examples of the alcohol include lower alcohols such as methanol, ethanol, propanol, isopropanol, and butanol, and ethanol is particularly preferable.
[0014]
Specific examples of the platinum ammine-based complex of the formula (1) include, for example, the following when ethanol is used as a solvent in the production thereof.
[0015]
Pt (IV) (NH 3 ) 2 (NO 2 ) 3 (OC 2 H 5 )
Pt (IV) (NO 2 ) 3 (OC 2 H 5 )
Pt (IV) (NH 3 ) 2 (NO 2 ) 2 (OC 2 H 5 ) (NO 3 )
Pt (II) (NH 3 ) (NO 2 ) (OC 2 H 5 )
[Pt (II) (NH 3 ) (NO 2 ) 2 (OC 2 H 5 )] H
[Pt (II) (NO 2 ) 3 (OC 2 H 5 )] H 2
Pt (IV) (NH 3 ) 2 (NO 2 ) 3 (COCH 3 )
Pt (II) (NH 3 ) 2 (NO 2 ) (COCH 3 )
[Pt (II) (NH 3 ) (NO 2 ) 2 (COCH 3 )] H
Pt (IV) (NH 3 ) 2 (NO 2 ) 3 (OCOCH 3 )
Pt (II) (NH 3 ) 2 (NO 2 ) (OCOCH3)
[Pt (II) (NH 3 ) (NO 2 ) 2 (OCOCH 3 )] H and the like.
[0016]
The platinum ammine complex of formula (1) produced as described above is diluted with an alcohol or an alcohol aqueous solution to form a supported solution composed of an alcohol solution of the platinum ammine complex. The amount of platinum metal in the supporting solution can generally be in the range of 1 to 40 g · dm −3, particularly preferably in the range of 2 to 30 g · dm −3. Further, when an alcohol solution of a platinum ammine complex is obtained using an alcohol aqueous solution, the alcohol concentration in the aqueous solution is usually 20 wt% or more, preferably 30 wt% or more.
[0017]
Carbon powder is immersed in the supporting solution prepared as described above. The amount of the supporting solution used for this dipping treatment may be more than the amount that the carbon powder is completely immersed, and the carbon powder can be a commercially available product as it is, but generally a method known per se (for example, It is more preferable to perform a hydrophilization treatment with nitric acid or the like in advance. The supporting solution in which the carbon powder is immersed is mixed for about 5 minutes with, for example, an ultrasonic homogenizer, and then the mixed solution is put into a container equipped with a reflux device and reduced at a temperature of 60 ° C. or higher, preferably 64 ° C. or higher. If the reduction temperature is lower than 60 ° C., the reduction takes a long time and is uneconomical. In addition, the upper limit of the reduction temperature is not particularly limited, but it is usually preferable that the reduction temperature be equal to or lower than the boiling point of the alcohol used. The reduction time depends on the ascorcol used and the reduction temperature, but can usually be about 2 to about 6 hours. A platinum-supported carbon powder catalyst in which platinum is supported in a highly dispersed state can be obtained by filtering, washing, and drying after the reduction treatment.
[0018]
【Example】
EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.
Example 1
Add 50 g of dinitrodiammine platinum salt in terms of platinum to 100 mL of a solution with a nitric acid concentration of 500 g · dm −3, mix and stir at 109 ° C. for 5 hours, and dissolve and age the dinitrodiammine platinum salt in nitric acid solution of trinitrodiammine platinum Got. Next, it was evaporated to dryness with a rotary evaporator at 80 ° C. to obtain a yellow brown powder. Ethanol was gradually added to this powder while maintaining it at 50 ° C. or lower to prepare a platinum ammine ethoxide complex solution having a platinum concentration of 50 g · dm −3. 720 mL of ethanol was added to 80 mL of this platinum ammine ethoxide complex solution to obtain an orange-red supported solution.
[0019]
To this support solution, 6.0 g of carbon powder “Vulcan XC-72R” (manufactured by Cabot) hydrophilized with a 60% nitric acid aqueous solution was added and mixed with an ultrasonic homogenizer. Thereafter, the supported solution was reduced with a rotary evaporator at 78 ° C. for 3 hours. The reaction solution was then filtered, washed with distilled water, and dried to obtain a carbon-supported platinum catalyst. The solution after filtration was colorless and transparent.
Example 2
After a nitric acid solution of trinitrodiammine platinum was obtained in the same manner as in Example 1, ethanol was gradually added to this solution while maintaining the temperature at 50 ° C. or lower to prepare a platinum concentration 50 g · dm −3 platinum ammine ethoxide complex solution. did. 720 mL of ethanol was added to 80 mL of this platinum ammine ethoxide complex solution to obtain an orange-red supported solution. To this support solution, 6.0 g of the same carbon powder as in Example 1 was added and mixed with an ultrasonic homogenizer. Thereafter, the supported solution was reduced with a rotary evaporator at 78 ° C. for 3 hours. The reaction solution was filtered, washed with distilled water, and dried to obtain a carbon-supported platinum catalyst. The solution after filtration was colorless and transparent.
Example 3
720 mL of 50% ethanol aqueous solution was added to 80 mL of platinum ammine ethoxide complex solution obtained in the same manner as in Example 1 to obtain an orange-red supported solution. To this support solution, 6.0 g of the same carbon powder as in Example 1 was added and mixed with an ultrasonic homogenizer. Thereafter, the supported solution was reduced with a rotary evaporator at 78 ° C. for 3 hours. The reaction solution was filtered, washed with distilled water, and dried to obtain a carbon-supported platinum catalyst. The solution after filtration was colorless and transparent.
Comparative Example 1
To the supporting solution of Example 1, 6.0 g of the same carbon powder as in Example 1 was added and mixed with an ultrasonic homogenizer. Thereafter, the supported solution was reduced with a rotary evaporator at 50 ° C. for 16 hours. The reaction solution was filtered, washed with distilled water, and dried to obtain a carbon-supported platinum catalyst. The solution after filtration was orange white.
Comparative Example 2
720 mL of distilled water was added to 80 mL of the platinum ammine ethoxide complex solution obtained in Example 1 to obtain an orange-red supported solution. To this support solution, 6.0 g of the same carbon powder as in Example 1 was added and mixed with an ultrasonic homogenizer. Thereafter, the supported solution was reduced with a rotary evaporator at 78 ° C. for 3 hours. The reaction solution was filtered, washed with distilled water, and dried to obtain a carbon-supported platinum catalyst. In addition, the solution after filtration was yellowish white.
Comparative Example 3
To the supporting solution of Example 1, 6.0 g of the same carbon powder as in Example 1 and 5.0 g of the aggregation inhibitor polyvinyl alcohol were added and mixed with an ultrasonic homogenizer. A 2.0% aqueous sodium borohydride solution (100 mL) was gradually added, and the mixture was reduced with stirring for 3 hours. This reaction solution was decanted with a 50% aqueous ethanol solution five times, filtered, washed with distilled water, and dried to obtain a carbon-supported platinum catalyst.
Comparative Example 4
6.0 g of the same carbon powder as in Example 1 is added to the support solution of Example 1, mixed with an ultrasonic homogenizer, and vacuum dried for 24 hours. The dry carbon powder was heated to 80 ° C. in a nitrogen atmosphere, then reduced by heat treatment under a 5% hydrogen-nitrogen stream for 20 hours to obtain a carbon-supported platinum catalyst. However, for about 30 minutes immediately after the start of reduction, the temperature was raised to 110 ° C. by the heat of reduction reaction, and the temperature could not be controlled.
Comparative Example 5
720 mL of ethanol was added to 80 mL of a commercially available dinitrodiammine platinum nitrate aqueous solution having a platinum concentration of 50 g · dm −3 to obtain a reddish brown support solution. To this support solution, 6.0 g of the same carbon powder as in Example 1 was added and mixed with an ultrasonic homogenizer. Thereafter, the supported solution was reduced with a rotary evaporator at 78 ° C. for 18 hours. The reaction solution was filtered, washed with distilled water, and dried to obtain a carbon-supported platinum catalyst. In addition, the solution after filtration was yellowish white.
[0020]
The amount of platinum in the supporting solutions of the above Examples and Comparative Examples and the amount of platinum supported on the carbon powder were determined, and the platinum supporting rate (%) was calculated from the following formula. The results are shown in Table 1.
[0021]
[Expression 1]
[0022]
As is clear from the results in Table 1, it can be seen that the catalysts of Examples 1 to 3 have a very high platinum loading ratio and a small crystallite diameter of platinum supported on carbon.
[0023]
[Table 1]
[0024]
Further, the electrodes produced using the carbon-supported platinum catalyst of Example 1 and Comparative Example 4 were joined to both surfaces of the proton conductive polymer electrolyte membrane Nafion 112 (manufactured by DuPont), and the performance as a fuel cell was measured. . The results are shown in FIG. As is clear from the results of FIG. 1, the carbon-supported catalysts of the examples are highly active and the battery performance is improved.
[0025]
【The invention's effect】
As described above, according to the method of the present invention, platinum can be supported with a small crystallite size and high dispersion, and further, the reduction operation time is short and it is not necessary to use a reducing gas. The manufacturing method of the catalyst excellent in the property and workability can be provided.
[Brief description of the drawings]
1 is a graph showing the results of measuring the performance of a fuel cell produced using the carbon-supported platinum catalysts of Example 1 and Comparative Example 4. FIG.
Claims (1)
[Pt(NH3)x(NO2)yL]Az
式中、
Ｌはアルコキシ基、アルカノイル基又はアルカノイルオキシ基を表し、
ＡはＨ、ＮＯ2又はＮＯ3を表し、
ｘは０、１又は２であり、そしてｙは１、２又は３であり、ただし、ｘとｙの合計は中心白金の電荷によって変わり３〜５であり、
ｚは中心金属の電荷によって変わり(ｙ−１)〜(ｙ−３)である、
で示される白金アンミン系錯体を溶存種として含有するアルコール溶液中にカーボン粉末を浸漬し、該溶液を６０℃以上の温度に加熱してカーボン粉末上に白金を析出させることを特徴とする白金担持触媒の製造方法。formula
[Pt (NH 3 ) x (NO 2 ) yL] Az
Where
L represents an alkoxy group, an alkanoyl group or an alkanoyloxy group,
A represents H, NO2 or NO3,
x is 0, 1 or 2, and y is 1, 2 or 3, provided that the sum of x and y varies from 3 to 5 depending on the charge of the central platinum;
z varies depending on the charge of the central metal and is (y-1) to (y-3).
A platinum support characterized in that carbon powder is immersed in an alcohol solution containing a platinum ammine complex as a dissolved species, and the solution is heated to a temperature of 60 ° C. or higher to deposit platinum on the carbon powder. A method for producing a catalyst.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP27737798A JP4082800B2 (en) | 1998-09-30 | 1998-09-30 | Catalyst production method |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP27737798A JP4082800B2 (en) | 1998-09-30 | 1998-09-30 | Catalyst production method |
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| JP4082800B2 true JP4082800B2 (en) | 2008-04-30 |
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| EP1511564A1 (en) | 2002-06-12 | 2005-03-09 | Sulzer Metco (Canada) Inc. | Hydrometallurgical process for production of supported catalysts |
| JP2005206931A (en) | 2003-12-26 | 2005-08-04 | Sumitomo Electric Ind Ltd | Method for producing metal powder |
| WO2005120703A1 (en) | 2004-06-10 | 2005-12-22 | Sumitomo Electric Industries, Ltd. | Metal catalyst and method for preparation thereof |
| JP2006286330A (en) * | 2005-03-31 | 2006-10-19 | Equos Research Co Ltd | Fuel cell and catalyst layer therefor |
| JP5157041B2 (en) * | 2005-03-31 | 2013-03-06 | 株式会社エクォス・リサーチ | Micro / nanocapsule, catalyst layer for fuel cell, fuel cell, and method for producing micro / nanocapsule |
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