JP2015188808A - Oxidation-reduction catalyst, electrode material, electrode, solar battery, membrane battery assembly for fuel battery, and fuel battery - Google Patents
Oxidation-reduction catalyst, electrode material, electrode, solar battery, membrane battery assembly for fuel battery, and fuel battery Download PDFInfo
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- 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
- Y02E60/50—Fuel cells
Abstract
Description
本発明は、触媒活性成分の脱落が抑えられ、長期にわたって高い触媒活性を維持可能な酸化還元触媒に関するものである。
また、本発明は、上記の酸化還元触媒を含有する電極材料、該電極材料を用いてなる電極、該電極をそなえる太陽電池および燃料電池用膜電極接合体、ならびに該燃料電池用膜電極接合体をそなえる燃料電池に関するものである。
The present invention relates to an oxidation-reduction catalyst that suppresses dropping of catalytically active components and can maintain high catalytic activity over a long period of time.
The present invention also provides an electrode material containing the oxidation-reduction catalyst, an electrode using the electrode material, a solar cell and fuel cell membrane electrode assembly having the electrode, and the fuel cell membrane electrode assembly. The present invention relates to a fuel cell having
近年、エネルギー問題や環境問題を解決する高効率な発電システムとして、太陽電池や燃料電池等が注目されている。 In recent years, solar cells and fuel cells have attracted attention as highly efficient power generation systems that solve energy and environmental problems.
このような太陽電池や燃料電池の電極には、通常、触媒として白金等の貴金属が使用されている。白金等の貴金属は非常に高価であることから、その使用量が電池の製造コストに大きく影響する。このため、白金等の貴金属の使用量を低減した電極用触媒の開発が望まれている。 In the electrodes of such solar cells and fuel cells, a noble metal such as platinum is usually used as a catalyst. Since noble metals such as platinum are very expensive, the amount used greatly affects the manufacturing cost of the battery. For this reason, development of the electrode catalyst which reduced the usage-amount of noble metals, such as platinum, is desired.
上記の要求に応えるものとして、炭素系触媒の表面に金属粒子が担持されてなる触媒が注目されている。
かかる触媒として、例えば、特許文献１には、カーボンナノチューブを酸化処理して該カーボンナノチューブ表面に開口部および欠陥部を形成し、前記金属触媒をカーボンナノチューブ内に固定することを特徴とするカーボンナノチューブに担持した金属触媒が開示されている。
As a response to the above requirements, a catalyst in which metal particles are supported on the surface of a carbon-based catalyst has attracted attention.
As such a catalyst, for example, Patent Document 1 discloses that a carbon nanotube is formed by oxidizing a carbon nanotube to form an opening and a defect on the surface of the carbon nanotube, and fixing the metal catalyst in the carbon nanotube. A metal catalyst supported on is disclosed.
しかし、特許文献１の技術では、分散処理の際に、カーボンナノチューブ（以下、ＣＮＴともいう）から金属粒子が脱落し易く、結果的に、太陽電池や燃料電池の電極における触媒層として製膜した場合に、十分な触媒活性を得られないという問題があった。 However, in the technique of Patent Document 1, metal particles easily fall off from carbon nanotubes (hereinafter also referred to as CNT) during the dispersion treatment, and as a result, a film is formed as a catalyst layer in an electrode of a solar cell or a fuel cell. In some cases, sufficient catalytic activity cannot be obtained.
本発明は、上記の問題を解決するために開発されたものであって、触媒活性成分の脱落が抑えられ、長期にわたって高い触媒活性を維持可能な酸化還元触媒を提供することを目的とする。
また、本発明は、上記の酸化還元触媒を含有する電極材料、該電極材料を用いてなる電極、該電極をそなえる太陽電池および燃料電池用膜電極接合体、ならびに該燃料電池用膜電極接合体をそなえる燃料電池を提供することを目的とする。
The present invention has been developed to solve the above-described problems, and an object of the present invention is to provide a redox catalyst that can prevent the catalytically active component from dropping and can maintain high catalytic activity over a long period of time.
The present invention also provides an electrode material containing the oxidation-reduction catalyst, an electrode using the electrode material, a solar cell and fuel cell membrane electrode assembly having the electrode, and the fuel cell membrane electrode assembly. An object of the present invention is to provide a fuel cell having the above.
発明者らは、上記の問題を解決すべく、触媒活性成分を担持した種々の炭素系触媒について、鋭意検討を行った。
その結果、触媒活性成分を担持する担体として、酸化処理によりその特性を適正に調整したＣＮＴ、具体的には、昇温脱離法における１５０〜９５０℃での一酸化炭素の脱離量および二酸化炭素の脱離量、ならびに窒素ガス吸着によるＢＥＴ比表面積を適正に調整したＣＮＴを使用することで、分散処理の際の触媒活性成分の脱落を防止でき、さらには分散性も向上するので触媒活性成分をＣＮＴに均一に担持することが可能となり、結果的に、長期にわたって高い触媒活性を維持可能な酸化還元触媒が得られることを知見した。
In order to solve the above-mentioned problems, the inventors diligently studied various carbon-based catalysts carrying a catalytically active component.
As a result, CNTs whose characteristics are appropriately adjusted by oxidation treatment as a carrier supporting a catalytically active component, specifically, the amount of carbon monoxide desorbed at 150 to 950 ° C. and carbon dioxide in the temperature programmed desorption method By using CNTs with appropriately adjusted carbon desorption amount and BET specific surface area by nitrogen gas adsorption, the catalytic active components can be prevented from falling off during the dispersion treatment, and further the dispersibility can be improved. It has been found that the components can be uniformly supported on the CNT, and as a result, a redox catalyst capable of maintaining high catalytic activity over a long period of time can be obtained.
また、酸化処理を施す原料ＣＮＴとしては後述するＳＧＣＮＴが、また酸化処理方法としては硝酸処理またはオゾン処理がそれぞれ特に好適であり、かようなＳＧＣＮＴの表面を硝酸処理またはオゾン処理することで、ＣＮＴの特性を上記のように有利に調整できることを併せて知見した。
本発明は、上記の知見に立脚するものである。
Further, SGCNT, which will be described later, is particularly suitable as the raw material CNT to be oxidized, and nitric acid treatment or ozone treatment is particularly suitable as the oxidation treatment method. By treating the surface of such SGCNT with nitric acid treatment or ozone treatment, CNT can be obtained. It has also been found that the characteristics of can be adjusted advantageously as described above.
The present invention is based on the above findings.
すなわち、本発明の要旨構成は次のとおりである。
１．酸化処理により、昇温脱離法における１５０〜９５０℃での一酸化炭素の脱離量を１０００〜２００００μｍｏｌ／ｇ、二酸化炭素の脱離量を５００〜１００００μｍｏｌ／ｇに、また窒素ガス吸着によるＢＥＴ比表面積を６００〜２８００ｍ２／ｇにそれぞれ調整したカーボンナノチューブに、触媒活性成分を担持してなる酸化還元触媒。
That is, the gist configuration of the present invention is as follows.
1. By oxidation treatment, the desorption amount of carbon monoxide at 150 to 950 ° C. in the temperature-programmed desorption method is 1000 to 20000 μmol / g, the desorption amount of carbon dioxide is 500 to 10,000 μmol / g, and BET by nitrogen gas adsorption is used. An oxidation-reduction catalyst comprising a carbon nanotube having a specific surface area adjusted to 600 to 2800 m 2 / g and carrying a catalytically active component.
２．前記カーボンナノチューブが、平均直径（Ａｖ）と直径の標準偏差（σ）が関係式：０．６０＞３σ／Ａｖ＞０．２０を満たすカーボンナノチューブを酸化処理したものである前記１記載の酸化還元触媒。 2. 2. The oxidation-reduction as described in 1 above, wherein the carbon nanotubes are obtained by oxidizing carbon nanotubes whose average diameter (Av) and standard deviation (σ) in diameter satisfy a relational expression: 0.60> 3σ / Av> 0.20. catalyst.
３．前記触媒活性成分が金属ナノ粒子または金属酸化物ナノ粒子である前記１または２記載の酸化還元触媒。 3. 3. The redox catalyst according to 1 or 2, wherein the catalytically active component is metal nanoparticles or metal oxide nanoparticles.
４．前記１〜３いずれかに記載の酸化還元触媒を含有する電極材料。 4). The electrode material containing the oxidation-reduction catalyst in any one of said 1-3.
５．前記４に記載の電極材料を用いてなる電極。 5. 5. An electrode using the electrode material described in 4 above.
６．前記５に記載の電極をそなえる太陽電池。 6). 6. A solar cell comprising the electrode according to 5 above.
７．前記５に記載の電極をそなえる燃料電池用膜電極接合体。 7). 6. A fuel cell membrane electrode assembly comprising the electrode as described in 5 above.
８．前記７に記載の燃料電池用膜電極接合体をそなえる燃料電池。 8). 8. A fuel cell comprising the fuel cell membrane electrode assembly as described in 7 above.
本発明によれば、触媒活性成分の脱落が抑えられ、長期にわたって高い触媒活性を維持可能な酸化還元触媒を得ることができる。
また、本発明の酸化還元触媒から、該酸化還元触媒を含有する電極材料、また該電極材料を用いてなる電極、さらには該電極をそなえる燃料電池用膜電極接合体を得ることができる。
そして、上記した電極および燃料電池用膜電極接合体を太陽電池および燃料電池の構成部材として用いることで、高い発電効率が得られる太陽電池および燃料電池を低コストで製造することが可能となる。
According to the present invention, it is possible to obtain an oxidation-reduction catalyst that can prevent the catalytically active component from falling off and can maintain high catalytic activity over a long period of time.
In addition, from the oxidation-reduction catalyst of the present invention, an electrode material containing the oxidation-reduction catalyst, an electrode using the electrode material, and a fuel cell membrane electrode assembly having the electrode can be obtained.
And it becomes possible to manufacture the solar cell and fuel cell which can obtain high electric power generation efficiency at low cost by using the above-mentioned electrode and membrane electrode assembly for fuel cells as a structural member of a solar cell and a fuel cell.
以下、本発明を具体的に説明する。まず、本発明の酸化還元触媒について説明する。 Hereinafter, the present invention will be specifically described. First, the oxidation-reduction catalyst of the present invention will be described.
［酸化還元触媒］
本発明の酸化還元触媒は、酸化処理により、昇温脱離法における１５０〜９５０℃での一酸化炭素の脱離量を１０００〜２００００μｍｏｌ／ｇ、二酸化炭素の脱離量を５００〜１００００μｍｏｌ／ｇに、また窒素ガス吸着によるＢＥＴ比表面積を６００〜２８００ｍ２／ｇにそれぞれ調整したカーボンナノチューブに、触媒活性成分を担持してなる酸化還元触媒である。
そこで、まず、本発明の酸化還元触媒で担体として使用するＣＮＴ（以下、担体ＣＮＴともいう）の特性について説明する。
[Redox catalyst]
The oxidation-reduction catalyst of the present invention is obtained by oxidation treatment so that the desorption amount of carbon monoxide at 150 to 950 ° C. in the temperature programmed desorption method is 1000 to 20000 μmol / g, and the desorption amount of carbon dioxide is 500 to 10,000 μmol / g. In addition, it is a redox catalyst in which a catalytic active component is supported on carbon nanotubes each having a BET specific surface area adjusted to 600 to 2800 m 2 / g by nitrogen gas adsorption.
Therefore, first, the characteristics of the CNT used as a carrier in the oxidation-reduction catalyst of the present invention (hereinafter also referred to as carrier CNT) will be described.
昇温脱離法における１５０〜９５０℃での一酸化炭素（ＣＯ）の脱離量が１０００〜２００００μｍｏｌ／ｇで、かつ二酸化炭素（ＣＯ２）の脱離量が５００〜１００００μｍｏｌ／ｇ
昇温脱離法（Temperature Programmed Desorption）において発生するガス中のＣＯとＣＯ２は、ＣＮＴ表面に結合している、水酸基、カルボキシル基、ケトン基、ラクトン基、アルデヒド基およびメチル基などの種々の官能基に由来する。上記したＣＯとＣＯ２の脱離量に調整するため、ＣＮＴの表面には、特に水酸基とカルボキシル基が多く存在しているものと考えられる。このため、本発明の酸化還元触媒で使用する担体ＣＮＴは、種々の溶媒への分散性に優れている。加えて、導電性にも優れている。
The desorption amount of carbon monoxide (CO) at 150 to 950 ° C. in the temperature programmed desorption method is 1000 to 20000 μmol / g, and the desorption amount of carbon dioxide (CO 2 ) is 500 to 10,000 μmol / g.
CO and CO 2 in the gas generated in the temperature programmed desorption method are variously bonded to the CNT surface, such as hydroxyl group, carboxyl group, ketone group, lactone group, aldehyde group and methyl group. Derived from a functional group. In order to adjust to the above-described desorption amount of CO and CO 2 , it is considered that there are particularly many hydroxyl groups and carboxyl groups on the surface of the CNT. For this reason, the carrier CNT used in the oxidation-reduction catalyst of the present invention is excellent in dispersibility in various solvents. In addition, it has excellent conductivity.
また、本発明では、上記したＣＯとＣＯ２の脱離量に調整したＣＮＴを使用することで、当該ＣＮＴからの触媒活性成分の脱落を防止できるのであるが、その理由について発明者らは次のように考えている。
すなわち、ＣＮＴ表面には水酸基やカルボキシル基が多く存在するものと推定されるが、これらの官能基との相互作用により、触媒活性成分である金属ナノ粒子等が固定されやすくなり、ＣＮＴからの触媒活性成分の脱落を防止できると考えられる。
なお、昇温脱離法におけるＣＯ脱離量とＣＯ２脱離量が前記所定の範囲より少ないと触媒活性成分が脱落しやすく、一方、多いとＣＮＴ自体の欠陥構造が多くなり、いずれにしても触媒活性が低下することになる。
Further, in the present invention, by using CNT adjusted to the above desorption amount of CO and CO 2 , it is possible to prevent the catalytic active component from falling off from the CNT. I think like that.
That is, it is presumed that there are many hydroxyl groups and carboxyl groups on the CNT surface, but the interaction with these functional groups makes it easy to fix metal nanoparticles, which are catalytically active components, and the catalyst from CNTs. It is thought that the active ingredient can be prevented from falling off.
Note that if the CO desorption amount and CO 2 desorption amount in the temperature-programmed desorption method are less than the predetermined range, the catalytically active component tends to fall off, whereas if the amount is large, the defect structure of the CNT itself increases. As a result, the catalytic activity is reduced.
ここに、上記した効果を得るためには、昇温脱離法における１５０〜９５０℃でのＣＯの脱離量を１０００〜２００００μｍｏｌ／ｇで、かつ二酸化炭素ＣＯ２の脱離量を５００〜１００００μｍｏｌ／ｇとする必要がある。
なお、ＣＯの脱離量は、好ましくは１５００〜１００００μｍｏｌ／ｇ、より好ましくは２０００〜８０００μｍｏｌ／ｇ、さらに好ましくは３０００〜６０００μｍｏｌ／ｇである。
また、ＣＯ２の脱離量は、好ましくは３００〜８０００μｍｏｌ／ｇ、より好ましくは５００〜５０００μｍｏｌ／ｇ、さらに好ましくは８００〜２０００μｍｏｌ／ｇである。
Here, in order to obtain the above effects, the desorption amount of CO at 150 to 950 ° C. in the temperature programmed desorption method is 1000 to 20000 μmol / g, and the desorption amount of carbon dioxide CO 2 is 500 to 10,000 μmol. / G.
The CO desorption amount is preferably 1500 to 10000 μmol / g, more preferably 2000 to 8000 μmol / g, and still more preferably 3000 to 6000 μmol / g.
The amount of CO 2 desorbed is preferably 300 to 8000 μmol / g, more preferably 500 to 5000 μmol / g, and still more preferably 800 to 2000 μmol / g.
なお、昇温脱離法におけるＣＯとＣＯ２の脱離量は、公知の方法により求めることができる。
すなわち、まず、所定の昇温脱離装置内において、ＣＮＴに熱処理を施すことにより、当該ＣＮＴの表面から吸着水脱離させる。次いで、この熱処理が施されたＣＮＴをヘリウムガス等の不活性ガス中で所定の温度まで加熱していき当該ＣＮＴの表面からの官能基（含酸素原子化合物など）の脱離に伴って発生するＣＯとＣＯ２とをそれぞれ定量する。
よって、昇温脱離法における１５０〜９５０℃でのＣＯの脱離量およびＣＯ２の脱離量は、ＣＮＴを１５０℃まで加熱し、その後、当該ＣＮＴをさらに加熱して、その温度が９５０℃に上昇するまでの間に脱離した、ＣＯの総量およびＣＯ２の総量として求められる。
The desorption amount of CO and CO 2 in the temperature programmed desorption method can be determined by a known method.
That is, first, heat treatment is performed on the CNTs in a predetermined temperature-programmed desorption device to desorb adsorbed water from the surface of the CNTs. Next, the heat-treated CNT is heated to a predetermined temperature in an inert gas such as helium gas, and is generated along with desorption of functional groups (oxygen-containing atomic compounds, etc.) from the surface of the CNT. Quantify CO and CO 2 respectively.
Therefore, the desorption amount of CO and the desorption amount of CO 2 at 150 to 950 ° C. in the temperature programmed desorption method are such that the CNT is heated to 150 ° C., and then the CNT is further heated so that the temperature is 950 It is determined as the total amount of CO and the total amount of CO 2 that have been desorbed before rising to ° C.
窒素ガス吸着によるＢＥＴ比表面積：６００〜２８００ｍ２／ｇ
本発明の酸化還元触媒で使用する担体ＣＮＴは、窒素吸着によるＢＥＴ比表面積を６００〜２８００ｍ２／ｇに調整する必要がある。なお、窒素吸着によるＢＥＴ比表面積は、ＣＮＴの全表面を対象とした比表面積に相当する。
ここに、窒素吸着によるＢＥＴ比表面積が上記の範囲にあることから、触媒活性成分の担持量を増やすことができ、触媒活性が向上する。また、官能基量も多くでき、触媒活性成分を多く担持しつつ脱落を防止できる。
なお、窒素吸着によるＢＥＴ比表面積が上記範囲より小さいと触媒活性成分を充分に担持させることが出来ず、触媒活性に劣り、一方、多いと所望のＣＮＴを得るのが非常に困難になる。
また、窒素吸着によるＢＥＴ比表面積を上記の範囲に調整し、さらに水蒸気吸着によるＢＥＴ比表面積を１０〜５００ｍ２／ｇの範囲に調整した場合には、ＣＮＴの全表面に親水性表面部分が存在することとなるので、分散性の向上という観点からは一層有利である。なお、水蒸気吸着によるＢＥＴ比表面積は、ＣＮＴの親水性表面部分を対象とした比表面積に相当する。
従って、本発明で使用する担体ＣＮＴにおける窒素ガス吸着によるＢＥＴ比表面積は、６００〜２８００ｍ２／ｇとする。好ましくは８００〜２５００ｍ２／ｇ、より好ましくは１０００〜２３００ｍ２／ｇ、さらに好ましくは１２００〜２０００ｍ２／ｇである。
また、水蒸気吸着によるＢＥＴ比表面積は１０〜５００ｍ２／ｇの範囲とすることが好ましく、より好ましくは３０〜３００ｍ２／ｇ、さらに好ましくは５０〜１５０ｍ２／ｇ、よりさらに好ましくは６０〜１３０ｍ２／ｇである。
BET specific surface area by nitrogen gas adsorption: 600-2800 m 2 / g
The carrier CNT used in the oxidation-reduction catalyst of the present invention needs to adjust the BET specific surface area by nitrogen adsorption to 600-2800 m 2 / g. The BET specific surface area by nitrogen adsorption corresponds to the specific surface area for the entire surface of the CNT.
Here, since the BET specific surface area by nitrogen adsorption is in the above range, the supported amount of the catalytically active component can be increased, and the catalytic activity is improved. Moreover, the amount of functional groups can be increased, and falling off can be prevented while supporting a large amount of catalytically active components.
If the BET specific surface area by nitrogen adsorption is smaller than the above range, the catalytically active component cannot be sufficiently supported and the catalytic activity is inferior. On the other hand, if the BET specific surface area is large, it is very difficult to obtain desired CNTs.
In addition, when the BET specific surface area by nitrogen adsorption is adjusted to the above range, and the BET specific surface area by water vapor adsorption is adjusted to the range of 10 to 500 m 2 / g, a hydrophilic surface portion is present on the entire surface of the CNT. Therefore, it is more advantageous from the viewpoint of improving dispersibility. In addition, the BET specific surface area by water vapor | steam adsorption is corresponded to the specific surface area which made the hydrophilic surface part of CNT object.
Therefore, the BET specific surface area by nitrogen gas adsorption in the carrier CNT used in the present invention is 600-2800 m 2 / g. Preferably 800~2500m 2 / g, more preferably 1000~2300m 2 / g, more preferably from 1200~2000m 2 / g.
Further, BET specific surface area by the adsorption of water vapor is preferably in the range of 10 to 500 m 2 / g, more preferably 30~300m 2 / g, more preferably 50 to 150 m 2 / g, more preferably more 60~130m 2 / g.
なお、窒素ガス吸着によるＢＥＴ比表面積および水蒸気吸着によるＢＥＴ比表面積は、７７Ｋにおける窒素吸着等温線および２９８Ｋにおける水蒸気吸着等温線をそれぞれ測定し、ＢＥＴ法により求めることができる。これらのＢＥＴ比表面積の測定は、例えば、「ＢＥＬＳＯＲＰ（登録商標）−ｍａｘ」（日本ベル（株）製）を用いて行うことができる。 The BET specific surface area by nitrogen gas adsorption and the BET specific surface area by water vapor adsorption can be determined by measuring the nitrogen adsorption isotherm at 77K and the water vapor adsorption isotherm at 298K, respectively, by the BET method. These BET specific surface areas can be measured using, for example, “BELSORP (registered trademark) -max” (manufactured by Nippon Bell Co., Ltd.).
以上、本発明の酸化還元触媒で使用する担体ＣＮＴの特性について説明したが、かような担体ＣＮＴは、原料ＣＮＴを酸化処理することで得ることができる。この酸化処理方法としては、公知の方法を特に限定なく採用することができるが、硝酸処理またはオゾン処理がそれぞれ特に好適である。
以下、原料ＣＮＴならびに好適な酸化処理である硝酸処理およびオゾン処理について説明する。
The characteristics of the carrier CNT used in the oxidation-reduction catalyst of the present invention have been described above. Such a carrier CNT can be obtained by oxidizing the raw material CNT. As this oxidation treatment method, a known method can be adopted without any particular limitation, but nitric acid treatment or ozone treatment is particularly suitable respectively.
Hereinafter, the raw material CNT and the nitric acid treatment and ozone treatment which are suitable oxidation treatments will be described.
（原料ＣＮＴ）
本発明の酸化還元触媒で使用する担体ＣＮＴの原料ＣＮＴとしては、表面にカーボンナノチューブ製造用触媒層（以下、「ＣＮＴ製造用触媒層」ということがある。）を有する基材（以下、「ＣＮＴ製造用基材」ということがある。）上に、原料化合物およびキャリアガスを供給して、化学的気相成長法（ＣＶＤ法）によりカーボンナノチューブを合成する際に、系内に微量の酸化剤を存在させることで、ＣＮＴ製造用触媒層の触媒活性を飛躍的に向上させるという方法（スーパーグロース法；国際公開第２００６／０１１６５５号参照）により得られるＣＮＴ（以下、ＳＧＣＮＴともいう）を用いることが好適である。
その理由としては、ＳＧＣＮＴは大きな比表面積を持ち、触媒活性成分を担持させるのに好都合であり、また、その構造特性に依存して適度な分散性が得られ、組織化させた場合に、触媒活性成分からの電子移動が生じやすいと考えられるためである。
(Raw material CNT)
As the raw material CNT of the carrier CNT used in the oxidation-reduction catalyst of the present invention, a substrate (hereinafter referred to as “CNT”) having a catalyst layer for producing carbon nanotubes (hereinafter sometimes referred to as “catalyst layer for producing CNT”) on the surface. When a raw material compound and a carrier gas are supplied onto the substrate to synthesize carbon nanotubes by a chemical vapor deposition method (CVD method), a small amount of oxidant is contained in the system. By using CNT (hereinafter also referred to as SGCNT) obtained by a method (supergrowth method; see International Publication No. 2006/011655) of dramatically improving the catalytic activity of the catalyst layer for CNT production Is preferred.
The reason for this is that SGCNT has a large specific surface area and is convenient for supporting a catalytically active component. Also, depending on its structural characteristics, moderate dispersibility can be obtained, and when it is organized, This is because electron transfer from the active component is likely to occur.
ここで、上記したＳＧＣＮＴは、その平均直径（Ａｖ）と直径の標準偏差（σ）が、通常、０．６０＞（３σ／Ａｖ）＞０．２０、好ましくは０．６０＞（３σ／Ａｖ）＞０．５０を満足する。
なお、直径とはＳＧＣＮＴの外径を意味する。また、平均直径（Ａｖ）および直径の標準偏差（σ）は、透過型電子顕微鏡での観察下に、無作為に選択されたカーボンナノチューブ１００本の直径を測定した際の平均値および標準偏差として求められる（後述する平均長さも、同様の方法で長さの測定を行い、その平均値として求められる。）。ＳＧＣＮＴとしては、そのようにして測定した直径を横軸に、その頻度を縦軸に取ってプロットし、ガウシアンで近似した際に、正規分布を取るものが通常使用される。
なお、ＳＧＣＮＴに対し酸化処理を行っても３σ／Ａｖの値は実質的に不変である。従って、酸化処理ＳＧＣＮＴは、その元となる未処理ＳＧＣＮＴと実質的に同様の３σ／Ａｖの値を有する。
Here, the SGCNT described above has an average diameter (Av) and a standard deviation (σ) of the diameter of usually 0.60> (3σ / Av)> 0.20, preferably 0.60> (3σ / Av )> 0.50 is satisfied.
The diameter means the outer diameter of SGCNT. The average diameter (Av) and the standard deviation of diameter (σ) are the average value and standard deviation when measuring the diameter of 100 randomly selected carbon nanotubes under observation with a transmission electron microscope. (The average length described later is also obtained as an average value by measuring the length in the same manner.) As the SGCNT, those having a normal distribution when the diameter measured in this way is plotted on the horizontal axis and the frequency is plotted on the vertical axis and approximated by Gaussian are usually used.
Note that the value of 3σ / Av is substantially unchanged even when the SGCNT is oxidized. Therefore, the oxidized SGCNT has a value of 3σ / Av that is substantially the same as that of the original untreated SGCNT.
また、ＳＧＣＮＴの平均直径（Ａｖ）は、通常、０．５〜１５ｎｍが好ましく、１ｎｍ〜１０ｎｍがより好ましい。
さらに、ＳＧＣＮＴの平均長さは、好ましくは０．１μｍ〜１ｃｍ、より好ましくは０．１μｍ〜１ｍｍである。
加えて、ＳＧＣＮＴの比表面積は、好ましくは１００〜２５００ｍ２／ｇ、より好ましくは４００〜１６００ｍ２／ｇである。ＳＧＣＮＴの比表面積が上記範囲内にあると、カーボンナノチューブの分散性がより高まる。なお、当該比表面積は、窒素ガス吸着によるＢＥＴ法により求めることができる。
Further, the average diameter (Av) of SGCNT is usually preferably from 0.5 to 15 nm, more preferably from 1 nm to 10 nm.
Furthermore, the average length of SGCNT is preferably 0.1 μm to 1 cm, more preferably 0.1 μm to 1 mm.
In addition, the specific surface area of SGCNT is preferably 100 to 2500 m 2 / g, more preferably 400 to 1600 m 2 / g. When the specific surface area of SGCNT is within the above range, the dispersibility of the carbon nanotubes is further increased. The specific surface area can be determined by the BET method using nitrogen gas adsorption.
また、ＳＧＣＮＴは、複数の微小孔を有するのが好ましい。中でも、孔径が２ｎｍよりも小さいマイクロ孔を有するのが好ましく、その存在量は、下記の方法で求めたマイクロ孔容積で、好ましくは０．４ｍＬ／ｇ以上、より好ましくは０．４３ｍＬ／ｇ以上、更に好ましくは０．４５ｍＬ／ｇ以上であり、上限としては、通常、０．６５ｍＬ／ｇ程度である。ＳＧＣＮＴが上記のようなマイクロ孔を有することは、ＳＧＣＮＴの分散性を高める観点から好ましい。なお、マイクロ孔容積は、例えば、ＳＧＣＮＴの調製方法および調製条件を適宜変更することで調整することができる。
ここで、「マイクロ孔容積（Ｖｐ）」は、ＳＧＣＮＴの液体窒素温度（７７Ｋ）での窒素吸脱着等温線を測定し、相対圧Ｐ／Ｐ０＝０．１９における窒素吸着量をＶとして、式（Ｉ）：Ｖｐ＝（Ｖ／２２４１４）×（Ｍ／ρ）より、算出することができる。なお、Ｐは吸着平衡時の測定圧力、Ｐ０は測定時の液体窒素の飽和蒸気圧であり、 式（Ｉ）中、Ｍは吸着質（窒素）の分子量２８．０１０、ρは吸着質（窒素）の７７Ｋにおける密度０．８０８ｇ／ｃｍ３である。マイクロ孔容積は、例えば、「ＢＥＬＳＯＲＰ（登録商標）−ｍｉｎｉ」（日本ベル（株）製）を使用して求めることができる。
SGCNT preferably has a plurality of micropores. Among them, it is preferable to have micropores having a pore size smaller than 2 nm, and the abundance thereof is a micropore volume determined by the following method, preferably 0.4 mL / g or more, more preferably 0.43 mL / g or more. More preferably, it is 0.45 mL / g or more, and the upper limit is usually about 0.65 mL / g. It is preferable that SGCNT have the above micropores from the viewpoint of improving the dispersibility of SGCNT. The micropore volume can be adjusted, for example, by appropriately changing the SGCNT preparation method and preparation conditions.
Here, the “micropore volume (Vp)” is an equation for measuring the nitrogen adsorption / desorption isotherm of SGCNT at the liquid nitrogen temperature (77 K), and assuming that the nitrogen adsorption amount at relative pressure P / P0 = 0.19 is V. (I): Vp = (V / 22414) × (M / ρ). P is the measurement pressure at the time of adsorption equilibrium, P0 is the saturated vapor pressure of liquid nitrogen at the time of measurement, and in formula (I), M is the molecular weight of adsorbate (nitrogen) 28.010, and ρ is the adsorbate (nitrogen). ) At 77K with a density of 0.808 g / cm 3. The micropore volume can be determined using, for example, “BELSORP (registered trademark) -mini” (manufactured by Nippon Bell Co., Ltd.).
なお、以上の特性を有するＳＧＣＮＴは、例えば、上述したスーパーグロース法において、基材表面への触媒層の形成をウェットプロセスにより行い、原料ガスとしてアセチレンを主成分とするガス（例えば、アセチレンを５０体積％以上含むガス）を用いることで、効率的に製造することができる。 Note that SGCNTs having the above characteristics are obtained by, for example, forming a catalyst layer on the surface of a base material by a wet process in the above-described super-growth method, and using acetylene as a main component gas (for example, 50% acetylene). By using a gas containing at least volume%, it can be efficiently produced.
（硝酸処理）
硝酸処理で用いる硝酸は、硝酸を含めば特に限定されず、発煙硝酸や、硫酸と混合した混酸も含む。通常、純度５％以上、好ましくは５０％以上、より好ましくは８０％以上のものを用いる。また、原料ＣＮＴ１００質量部に対し、通常、硝酸を２００〜１００００質量部添加する。その際、得られた混合物を超音波処理し、原料ＣＮＴを分散させてもよい。
次いで、得られた混合物を加熱してもよい。加熱方法は通常用いられる方法なら特に限定されないが、オイルバスやマントルヒーターでの加熱、マイクロ波を照射して加熱する方法など適時選択すればよい。加熱は常圧またはオートクレーブ中など加圧下で実施してもよい。加熱は、通常、常圧の場合、３０〜１２０℃で０．１〜５０時間、加圧の場合、３０〜２００℃で０．１〜５０時間程度行う。一方、マイクロ波照射による加熱は、通常、常圧の場合、３０〜１２０℃で、加圧の場合、３０〜２００℃で、前記混合物が加熱されるようにマイクロ波の出力を設定して、０．０１〜２４時間程度行う。いずれの場合も、加熱は一段階で行っても二段階以上で行ってもよい。また、加熱時には、前記混合物を任意の撹拌手段により撹拌するのが好ましい。
以上により、原料ＣＮＴの表面を硝酸処理することができるが、当該処理終了後の混合物は非常に高温であるため、室温まで冷却する。次いで、硝酸を、例えば、デカンテーションにより除去し、処理後のＣＮＴを、例えば、水で洗浄する。当該洗浄は、通常、洗浄排水が中性になるまで行う。
(Nitric acid treatment)
The nitric acid used in the nitric acid treatment is not particularly limited as long as it includes nitric acid, and includes fuming nitric acid and mixed acid mixed with sulfuric acid. Usually, the purity is 5% or more, preferably 50% or more, more preferably 80% or more. Moreover, 200-10000 mass parts of nitric acid is normally added with respect to 100 mass parts of raw material CNT. At that time, the obtained mixture may be subjected to ultrasonic treatment to disperse the raw material CNT.
The resulting mixture may then be heated. The heating method is not particularly limited as long as it is a commonly used method, but may be selected as appropriate, such as heating with an oil bath or mantle heater, or heating by irradiating microwaves. Heating may be performed under normal pressure or under pressure such as in an autoclave. In general, heating is performed at 30 to 120 ° C. for 0.1 to 50 hours in the case of normal pressure, and in the case of pressurization, the heating is performed at 30 to 200 ° C. for about 0.1 to 50 hours. On the other hand, heating by microwave irradiation is usually set at 30 to 120 ° C. for normal pressure, and 30 to 200 ° C. for pressurization, setting the microwave output so that the mixture is heated, Perform for about 0.01 to 24 hours. In either case, heating may be performed in one step or in two or more steps. Moreover, it is preferable to stir the said mixture by arbitrary stirring means at the time of a heating.
As described above, the surface of the raw material CNT can be treated with nitric acid. However, since the mixture after the completion of the treatment is very high temperature, it is cooled to room temperature. Next, nitric acid is removed by, for example, decantation, and the treated CNTs are washed with, for example, water. The washing is usually performed until the washing wastewater becomes neutral.
（オゾン処理）
オゾン処理は、原料ＣＮＴを容器に入れ、原料ＣＮＴの温度を、通常、０〜１００℃、好ましくは２０〜５０℃の範囲になるように調整しながら、オゾン発生装置より、通常、常圧の圧力で該容器にオゾン含有ガスを導き、通常、１〜７２０分間、好ましくは３０〜６００分間反応させることで行うことができる。
オゾンガスは、空気または窒素で希釈され、通常、０．０１〜１００ｇ／Ｎｍ３、好ましくは１〜７０ｇ／Ｎｍ３、より好ましくは１０〜５０ｇ／Ｎｍ３である。湿度は、特に限定されないが２０〜９０ＲＨ％の通常範囲である。
以上により、原料ＣＮＴの表面がオゾン処理されるが、オゾン処理は、硫酸や硝酸など、液体の酸化剤を用いた表面処理とは異なり、ガスで行うことができるため、反応終了後、得られたＣＮＴを、直ちに乾燥固体として使用することができる。
(Ozone treatment)
In the ozone treatment, the raw material CNT is put in a container, and the temperature of the raw material CNT is usually adjusted to a range of 0 to 100 ° C., preferably 20 to 50 ° C. It can be carried out by introducing an ozone-containing gas into the vessel under pressure and reacting for 1 to 720 minutes, preferably 30 to 600 minutes.
Ozone gas is diluted with air or nitrogen, usually, 0.01 to 100 g / Nm 3, preferably 1~70g / Nm 3, more preferably 10 to 50 g / Nm 3. Although humidity is not specifically limited, it is a normal range of 20-90RH%.
As described above, the surface of the raw material CNT is subjected to ozone treatment. Unlike the surface treatment using a liquid oxidizing agent such as sulfuric acid or nitric acid, the ozone treatment can be performed with gas, and thus obtained after completion of the reaction. The CNT can be used immediately as a dry solid.
次に、本発明の酸化還元触媒で使用する触媒活性成分について説明する。
本発明の酸化還元触媒で使用する触媒活性成分としては、典型的には、金属ナノ粒子や金属酸化物ナノ粒子が挙げられる（以下、金属ナノ粒子と金属酸化物ナノ粒子をまとめて「金属ナノ粒子等」ともいう）。
Next, the catalytically active component used in the redox catalyst of the present invention will be described.
The catalytically active component used in the oxidation-reduction catalyst of the present invention typically includes metal nanoparticles and metal oxide nanoparticles (hereinafter, metal nanoparticles and metal oxide nanoparticles are collectively referred to as “metal nanoparticles”). Also called “particles”).
ここで、金属ナノ粒子の平均粒径は、好ましくは０．５〜１５ｎｍであり、粒径の標準偏差は、好ましくは１．５ｎｍ以下である。また、金属酸化物ナノ粒子の平均粒径は、好ましくは１〜２０ｎｍであり、粒径の標準偏差は、好ましくは３ｎｍ以下である。
なお、金属ナノ粒子等の平均粒径と粒径の標準偏差は、透過型電子顕微鏡で観察し、無作為に選択された１００個の金属ナノ粒子等の画像に基づいてその粒径を測定し、求めることができる。
Here, the average particle diameter of the metal nanoparticles is preferably 0.5 to 15 nm, and the standard deviation of the particle diameter is preferably 1.5 nm or less. The average particle diameter of the metal oxide nanoparticles is preferably 1 to 20 nm, and the standard deviation of the particle diameter is preferably 3 nm or less.
The average particle size and standard deviation of the particle size of the metal nanoparticles are observed with a transmission electron microscope, and the particle size is measured based on images of 100 randomly selected metal nanoparticles. Can be sought.
金属ナノ粒子等の形状としては、特に限定されるものではなく、例えば、球状；立方体；長方形；六角板状など板状；柱状；六角棒状など棒状；などが挙げられ、コア部とシェル部で金属成分が異なるコアシェル構造体であってもよい。 The shape of the metal nanoparticles or the like is not particularly limited, and examples thereof include a spherical shape, a cubic shape, a rectangular shape, a plate shape such as a hexagonal plate shape, a column shape, a rod shape such as a hexagonal rod shape, and the like. Core-shell structures with different metal components may be used.
金属ナノ粒子等としては、周期律表第４族〜第１４族の金属および金属酸化物のナノ粒子が挙げられる。
周期律表第４族〜第１４族の金属としては、Ｔｉ、Ｖ、Ｃｒ、Ｍｎ、Ｆｅ、Ｃｏ、Ｎｉ、Ｃｕ、Ｚｎ、Ｇａ、Ｚｒ、Ｒｕ、Ｒｈ、Ｐｄ、Ａｇ、Ｃｄ、Ｓｎ、Ｈｆ、Ｗ、Ｒｅ、Ｉｒ、Ｐｔ、Ａｕ、Ｐｂ等が挙げられる。なかでも、太陽電池および燃料電池用の触媒層として用いる場合、より触媒活性に優れる触媒層を形成し易いことから、白金（Ｐｔ）が好ましい。
金属ナノ粒子等は、１種単独で、あるいは２種以上を組み合わせて用いることができる。また、金属ナノ粒子等は単独の金属からなっても、または複数種類の金属からなる合金からなってもよい。
Examples of the metal nanoparticles include nanoparticles of metals and metal oxides of Groups 4 to 14 of the periodic table.
The metals in Groups 4 to 14 of the periodic table include Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Zr, Ru, Rh, Pd, Ag, Cd, Sn, and Hf. , W, Re, Ir, Pt, Au, Pb and the like. Of these, platinum (Pt) is preferred when used as a catalyst layer for solar cells and fuel cells because a catalyst layer with better catalytic activity can be easily formed.
A metal nanoparticle etc. can be used individually by 1 type or in combination of 2 or more types. The metal nanoparticles or the like may be made of a single metal or an alloy made of a plurality of types of metals.
また、担体ＣＮＴにおける金属ナノ粒子等の担持量は特に限定されないが、ＣＮＴ１００質量部あたり、１質量部以上が好ましい。金属ナノ粒子等の担持量が１質量部以上であることで、触媒層としてより有用な導電膜を形成し易くなる。金属ナノ粒子等の担持量は多ければ多いほど触媒活性は高くなると考えられるが、ＣＮＴの担持能や経済性を考慮すれば、金属ナノ粒子等の担持量の上限は、ＣＮＴ１００質量部あたり、通常、３０，０００質量部以下である。 Further, the amount of metal nanoparticles or the like supported on the carrier CNT is not particularly limited, but is preferably 1 part by mass or more per 100 parts by mass of the CNT. When the supported amount of metal nanoparticles or the like is 1 part by mass or more, it becomes easier to form a conductive film more useful as a catalyst layer. The more the amount of metal nanoparticles and the like supported, the higher the catalytic activity. However, considering the CNT supportability and economy, the upper limit of the amount of metal nanoparticles and the like is usually about 100 parts by mass of CNTs. 30,000 parts by mass or less.
なお、金属ナノ粒子等をＣＮＴに担持させる方法は特に限定されず、公知の方法に従えばよい。例えば、ＣＮＴに金属ナノ粒子を担持する場合は、金属ナノ粒子を生成する金属前駆体、ＣＮＴおよび還元剤を含む混合液を調製し、金属前駆体由来の陽イオンを還元剤により還元することで、ＣＮＴ上に金属ナノ粒子を担持することができる。前記還元剤としては、例えば、エチレングリコールなどのアルコール化合物や水素化ホウ素ナトリウムなどが挙げられる。また、ＣＮＴに金属酸化物ナノ粒子を担持する場合は、金属酸化物ナノ粒子を生成する金属酸化物前駆体、ＣＮＴおよびアルコール化合物を含む混合液を調製し、該混合液に水を添加し、金属酸化物前駆体を加水分解・縮合反応させることで、ＣＮＴ上に金属酸化物ナノ粒子を担持することができる。 In addition, the method of carrying | supporting a metal nanoparticle etc. on CNT is not specifically limited, What is necessary is just to follow a well-known method. For example, when metal nanoparticles are supported on CNTs, a mixed solution containing a metal precursor that generates metal nanoparticles, CNTs, and a reducing agent is prepared, and a cation derived from the metal precursor is reduced with a reducing agent. The metal nanoparticles can be supported on the CNTs. Examples of the reducing agent include alcohol compounds such as ethylene glycol and sodium borohydride. In addition, when supporting metal oxide nanoparticles on CNTs, prepare a mixed solution containing a metal oxide precursor that generates metal oxide nanoparticles, CNTs, and an alcohol compound, add water to the mixed solution, By subjecting the metal oxide precursor to hydrolysis / condensation reaction, the metal oxide nanoparticles can be supported on the CNTs.
ここで、前記金属前駆体は、還元反応により金属ナノ粒子を形成し得る化合物である。金属酸化物前駆体は、加水分解・縮合反応により金属酸化物ナノ粒子を形成し得る化合物である。金属前駆体および金属酸化物前駆体は、所望の金属ナノ粒子および金属酸化物ナノ粒子が得られ、かつ、用いる溶媒に溶解するものであれば、特に限定されない。 Here, the metal precursor is a compound capable of forming metal nanoparticles by a reduction reaction. A metal oxide precursor is a compound that can form metal oxide nanoparticles by hydrolysis and condensation reactions. The metal precursor and the metal oxide precursor are not particularly limited as long as desired metal nanoparticles and metal oxide nanoparticles can be obtained and can be dissolved in a solvent to be used.
この金属前駆体の具体例としては、（ＮＨ４）２［ＲｕＣｌ６］、（ＮＨ４）２［ＲｕＣｌ５（Ｈ２Ｏ）］、Ｈ２ＰｔＣｌ４、Ｈ２ＰｔＣｌ６、Ｋ２ＰｔＣｌ４、Ｋ２ＰｔＣｌ６、Ｈ２［ＡｕＣｌ４］、（ＮＨ４）２［ＡｕＣｌ４］、Ｈ［Ａｕ（ＮＯ３）４］Ｈ２Ｏ等が挙げられるが、これらに限定されるものではない。
また、金属酸化物前駆体の具体例としては、Ｔｉ（ＯＣＨ３）４、Ｔｉ（ＯＣ２Ｈ５）４、Ｔｉ（ＯｎＣ３Ｈ７）４、Ｔｉ（ＯｉＣ３Ｈ７）４、Ｔｉ（ＯＣ４Ｈ９）４、ＴｉＣｌ４、Ｚｒ（ＯＣＨ３）４、Ｚｒ（ＯＣ２Ｈ５）４、Ｚｒ（ＯｎＣ３Ｈ７）４、ＺｒＯｉＣ３Ｈ７）４、Ｚｒ（ＯＣ４Ｈ９）４、ＺｒＣｌ４、Ｈｆ（ＯＣＨ３）４、Ｈｆ（ＯＣ２Ｈ５）４、Ｈｆ（ＯｎＣ３Ｈ７）４、Ｈｆ（ＯｉＣ３Ｈ７）４、Ｈｆ（ＯＣ４Ｈ９）４、ＨｆＣｌ４等が挙げられるが、これらに限定されない。
金属前駆体および金属酸化物前駆体は、それぞれ１種単独で、あるいは２種以上を組み合わせて用いることができる。
Specific examples of the metal precursor include (NH 4 ) 2 [RuCl 6 ], (NH 4 ) 2 [RuCl 5 (H 2 O)], H 2 PtCl 4 , H 2 PtCl 6 , K 2 PtCl 4 , Examples thereof include, but are not limited to, K 2 PtCl 6 , H 2 [AuCl 4 ], (NH 4 ) 2 [AuCl 4 ], H [Au (NO 3 ) 4 ] H 2 O, and the like.
Specific examples of the metal oxide precursor include Ti (OCH 3 ) 4 , Ti (OC 2 H 5 ) 4 , Ti (OnC 3 H 7 ) 4 , Ti (OiC 3 H 7 ) 4 , Ti (OC). 4 H 9 ) 4 , TiCl 4 , Zr (OCH 3 ) 4 , Zr (OC 2 H 5 ) 4 , Zr (OnC 3 H 7 ) 4 , ZrOiC 3 H 7 ) 4 , Zr (OC 4 H 9 ) 4 , ZrCl 4 , Hf (OCH 3 ) 4 , Hf (OC 2 H 5 ) 4 , Hf (OnC 3 H 7 ) 4 , Hf (OiC 3 H 7 ) 4 , Hf (OC 4 H 9 ) 4 , HfCl 4, etc. For example, but not limited to.
Each of the metal precursor and the metal oxide precursor can be used alone or in combination of two or more.
なお、上記の担体ＣＮＴは、溶媒への分散性に優れたものであることから、その分散には、通常、分散剤を必要としない。
また、混合処理や分散処理は、例えば、ナノマイザー、アルティマイザー、超音波分散機、ボールミル、サンドグラインダー、ダイノミル、スパイクミル、ＤＣＰミル、バスケットミル、ペイントコンディショナー、ジェットミル、高速薄膜旋回装置、高速攪拌装置等を用いる方法を利用すればよい。
In addition, since said carrier CNT is excellent in the dispersibility to a solvent, a dispersing agent is not normally required for the dispersion | distribution.
The mixing process and dispersion process are, for example, nanomizer, optimizer, ultrasonic disperser, ball mill, sand grinder, dyno mill, spike mill, DCP mill, basket mill, paint conditioner, jet mill, high-speed thin film swirler, and high-speed stirring. A method using an apparatus or the like may be used.
［電極材料］
次に、本発明の電極材料について説明する。
本発明の電極材料は、上述した酸化還元触媒を含有することを特徴とする。このような電極材料としては、例えば、触媒層形成用分散液や、当該触媒層形成用分散液から得られる太陽電池や燃料電池の電極の触媒層（導電膜を兼ねる触媒層も含む）が挙げられる。
[Electrode material]
Next, the electrode material of the present invention will be described.
The electrode material of the present invention is characterized by containing the above-described oxidation-reduction catalyst. Examples of such an electrode material include a catalyst layer forming dispersion, and a catalyst layer (including a catalyst layer also serving as a conductive film) of a solar cell or a fuel cell obtained from the catalyst layer forming dispersion. It is done.
ここに、触媒層形成用分散液の調製に用いる溶媒としては、前述した担体ＣＮＴを分散させる場合と同様のものが挙げられる。また、触媒層形成用分散液は、本発明の効果を阻害しない範囲で、さらに、導電材、例えばケッチェンブラック（ＫＢ）等を含有させてもよい。
また、触媒層形成用分散液は、本発明の酸化還元触媒を溶媒中にて前記担体ＣＮＴを分散させる場合と同様の混合処理および分散処理を行うことで得ることができる。
なお、触媒層形成用分散液中の酸化還元触媒の含有量は、特に限定されないが、分散液全体中、好ましくは０．００１〜１０質量％である。
Here, examples of the solvent used for preparing the dispersion for forming the catalyst layer include the same solvents as those used for dispersing the carrier CNT described above. The dispersion for forming the catalyst layer may further contain a conductive material such as ketjen black (KB) as long as the effects of the present invention are not impaired.
The dispersion for forming the catalyst layer can be obtained by performing the same mixing treatment and dispersion treatment as in the case of dispersing the carrier CNT in the solvent of the oxidation-reduction catalyst of the present invention.
The content of the redox catalyst in the dispersion for forming the catalyst layer is not particularly limited, but is preferably 0.001 to 10% by mass in the entire dispersion.
［電極］
次に、本発明の電極について説明する。
本発明の電極は、上述した電極材料を用いてなることを特徴とし、具体的には、色素増感型太陽電池の対向電極や燃料電池用の空気極および燃料極等が挙げられる。なお、後述するように、燃料電池用の空気極および燃料極は、通常、拡散層と触媒層から構成される。
[electrode]
Next, the electrode of the present invention will be described.
The electrode of the present invention is characterized by using the electrode material described above, and specifically includes a counter electrode of a dye-sensitized solar cell, an air electrode and a fuel electrode for a fuel cell, and the like. As will be described later, the air electrode and the fuel electrode for a fuel cell are usually composed of a diffusion layer and a catalyst layer.
ここで、例えば、色素増感型太陽電池の対向電極を形成する場合には、基材となる支持体に形成した導電膜上に、上述した触媒層形成用分散液を塗布し、得られた塗膜を乾燥させた触媒層を形成することで、対向電極を形成することができる。
また、触媒層が導電膜を兼ねる場合には、基材となる支持体上に、上述した触媒層形成用分散液を塗布し、得られた塗膜を乾燥させた触媒層を形成することで、対向電極を形成することができる。
なお、触媒層または導電膜を兼ねる触媒層を別途形成し、これらを用いて色素増感型太陽電池の対向電極を形成してもよい。
Here, for example, when the counter electrode of the dye-sensitized solar cell is formed, the above-described dispersion for forming a catalyst layer is applied onto the conductive film formed on the support serving as the base material. The counter electrode can be formed by forming a catalyst layer in which the coating film is dried.
In addition, when the catalyst layer also serves as the conductive film, the catalyst layer forming dispersion liquid described above is applied on the support as the base material, and the resulting coating film is dried to form a catalyst layer. A counter electrode can be formed.
Alternatively, a catalyst layer that also serves as a catalyst layer or a conductive film may be separately formed, and these may be used to form the counter electrode of the dye-sensitized solar cell.
［太陽電池］
次に、本発明の太陽電池について説明する。
本発明の太陽電池は、上述した電極をそなえることを特徴とする。本発明の太陽電池としては、例えば、図１に示すように光電極１０、電解質層２０、対向電極３０がこの順に並んでなる構造を有し、対向電極３０として本発明の電極をそなえる色素増感型太陽電池が挙げられる。
図１中、符号１０ａは光電極基板、１０ｂは多孔質半導体微粒子層、１０ｃは増感色素層、１０ｄ、３０ａは支持体、１０ｅ、３０ｃは導電膜、３０ｂは触媒層である。
かかる色素増感型太陽電池は、光電極、電解質層、対向電極の他に、保護層、反射防止層、ガスバリア層等の機能層を有していてもよい。また、上述したように、本発明の電極を使用する場合、触媒層が導電膜を兼ねることもできる。
また、本発明の太陽電池は、本発明の酸化還元触媒を含有する電極材料を用いてなる電極をそなえるので、発電効率が高く、耐久性に優れる。
なお、電極以外の構成については、従来公知のものを用いればよい。
[Solar cell]
Next, the solar cell of the present invention will be described.
The solar cell of the present invention includes the above-described electrode. The solar cell of the present invention has, for example, a structure in which a
In FIG. 1,
Such a dye-sensitized solar cell may have functional layers such as a protective layer, an antireflection layer, and a gas barrier layer in addition to the photoelectrode, the electrolyte layer, and the counter electrode. Moreover, as mentioned above, when using the electrode of this invention, a catalyst layer can also serve as an electrically conductive film.
Moreover, since the solar cell of this invention is equipped with the electrode which uses the electrode material containing the oxidation-reduction catalyst of this invention, electric power generation efficiency is high and it is excellent in durability.
In addition, about a structure other than an electrode, what is known conventionally may be used.
［燃料電池用膜電極接合体］
次に、本発明の燃料電池用膜電極接合体について説明する。
本発明の燃料電池用膜電極接合体（ＭＥＡ）は、上述した電極を空気極および／または燃料極としてそなえることを特徴とし、例えば、図２に示すように燃料電池用膜電極接合体６０の両側に位置するセパレータ５０とともに、固体高分子型燃料電池を構成する。また、本発明の燃料電池用膜電極接合体としては、例えば、図２に示すように空気極７０、電解質膜８０、燃料極９０がこの順に並んでなる構造を有し、空気極７０および／または燃料極９０として本発明の電極をそなえる固体高分子型燃料電池が挙げられる。
図２中、符号７０ａはカソード側拡散層、７０ｂはカソード側触媒層、９０ａはアノード側拡散層、９０ｂはカソード側触媒層である。
なお、電解質膜やガス拡散層等の構成については、従来公知のものを用いればよい。
[Membrane electrode assembly for fuel cells]
Next, the membrane electrode assembly for fuel cells of the present invention will be described.
The fuel cell membrane electrode assembly (MEA) of the present invention is characterized in that the above-described electrode is provided as an air electrode and / or a fuel electrode. For example, as shown in FIG. Together with the
In FIG. 2,
In addition, what is necessary is just to use conventionally well-known things about structures, such as an electrolyte membrane and a gas diffusion layer.
［燃料電池］
次に、本発明の燃料電池について説明する。
本発明の燃料電池は、上述した燃料電池用膜電極接合体をそなえることを特徴とする。
本発明の燃料電池の具体例としては、例えば、燃料電池用膜電極接合体（ＭＥＡ）と、その両側に位置するセパレータとを具える固体高分子型燃料電池が挙げられる。
本発明の燃料電池は、上記した燃料電池用膜電極接合体をそなえ、当該燃料電池用膜電極接合体は、本発明の酸化還元触媒を含有する電極材料を用いてなる電極により構成されるので、発電効率が高く、耐久性に優れる。
なお、セパレータについては、従来公知のものを用いればよい。
[Fuel cell]
Next, the fuel cell of the present invention will be described.
The fuel cell of the present invention comprises the above-described membrane electrode assembly for a fuel cell.
Specific examples of the fuel cell of the present invention include a polymer electrolyte fuel cell comprising a fuel cell membrane electrode assembly (MEA) and separators located on both sides thereof.
The fuel cell of the present invention includes the above-described membrane electrode assembly for a fuel cell, and the membrane electrode assembly for a fuel cell is constituted by an electrode using the electrode material containing the oxidation-reduction catalyst of the present invention. High power generation efficiency and excellent durability.
In addition, what is necessary is just to use a conventionally well-known thing about a separator.
以下、本発明について実施例に基づき具体的に説明するが、本発明はこれらの実施例に限定されるものではない。なお、物性等の評価は、以下の方法により行った。 EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited to these Examples. The physical properties were evaluated by the following methods.
（１）ＢＥＴ比表面積
日本ベル社製「ＢＥＬＳＯＲＰ（登録商標）−ｍａｘ」を用い、窒素（温度：７７Ｋ）および蒸留水（温度：２９８Ｋ）の吸着等温線を測定し、ＢＥＴ法により、ＣＮＴの窒素吸着によるＢＥＴ比表面積と水蒸気吸着によるＢＥＴ比表面積とを求めた。
（２）昇温脱離法による評価
日本ベル社製の全自動昇温脱離スペクトル装置「ＴＰＤ−1−ＡＴｗ」にＣＮＴを設置し、キャリヤーガス（Ｈｅ）を５０ｍＬ／分で流通させた。ＣＯおよびＣＯ２の脱離量は、５℃／分の昇温速度で１５０℃から９５０℃に昇温してＣＮＴを加熱し、その間に生じたＣＯおよびＣＯ２を四重極質量分析計で検出し、得られたＣＯおよびＣＯ２のガス量からＣＮＴの１ｇあたりから生ずるガスの量（μｍｏｌ）を計算し、ＣＯおよびＣＯ２の脱離量をそれぞれ求めた。
（３）触媒活性成分の担体ＣＮＴからの脱落評価
超音波分散機で分散処理後の溶液を、ＴＥＭ（透過型電子顕微鏡 日立製）を用いて評価し、凝集物の有無を目視で確認し、以下の基準で触媒活性成分の担体ＣＮＴからの脱落を評価した。
○：任意の視野で観察される複数粒子の凝集体の数が５個未満
×：任意の視野で観察される複数粒子の凝集体の数が５個以上
(1) BET specific surface area Adsorption isotherm of nitrogen (temperature: 77K) and distilled water (temperature: 298K) was measured using “BELSORP (registered trademark) -max” manufactured by Nippon Bell Co., Ltd. The BET specific surface area by nitrogen adsorption and the BET specific surface area by water vapor adsorption were determined.
(2) Evaluation by temperature programmed desorption method CNT was installed in a fully automatic temperature programmed desorption spectrum apparatus “TPD-1-ATw” manufactured by Bell Japan Co., Ltd., and a carrier gas (He) was circulated at 50 mL / min. The amount of CO and CO 2 desorbed was increased from 150 ° C. to 950 ° C. at a rate of temperature increase of 5 ° C./min to heat the CNT, and the CO and CO 2 produced during that time were measured with a quadrupole mass spectrometer. detecting the amount of gas generated from per 1g of CNT from the amount of gas resulting CO and CO 2 ([mu] mol) was calculated and determined the amount of released CO and CO 2, respectively.
(3) Evaluation of dropout of catalyst active component from carrier CNT The solution after dispersion treatment with an ultrasonic disperser is evaluated using TEM (transmission electron microscope, manufactured by Hitachi), and the presence or absence of aggregates is visually confirmed. The removal of the catalytically active component from the carrier CNT was evaluated according to the following criteria.
○: The number of aggregates of multiple particles observed in an arbitrary field of view is less than 5 ×: The number of aggregates of multiple particles observed in an arbitrary field of view is 5 or more
［原料ＣＮＴの合成］
国際公開第２００６／０１１６５５号パンフレットの記載に従って、スーパーグロース法によりＳＧＣＮＴを調製した。
得られたＳＧＣＮＴは、主に単層ＣＮＴから構成され、ＢＥＴ比表面積が８００ｍ２／ｇ、マイクロ孔容積が０．４４ｍＬ／ｇであった。また、平均直径（Ａｖ）が３．３ｎｍ、直径分布（３σ）が１．９ｎｍ、（３σ／Ａｖ）が０．５８であり、平均長さが５００μｍであった。
[Synthesis of raw material CNT]
SGCNT was prepared by the super-growth method according to the description in WO 2006/011655.
The obtained SGCNT was mainly composed of single-walled CNTs, and had a BET specific surface area of 800 m 2 / g and a micropore volume of 0.44 mL / g. The average diameter (Av) was 3.3 nm, the diameter distribution (3σ) was 1.9 nm, (3σ / Av) was 0.58, and the average length was 500 μm.
［酸化処理］
５００ｍＬ容ナスフラスコに、上記で合成したＳＧＣＮＴを１g入れ、エバポレーターに接続した。エバポレーターのガス流路に、オゾン発生装置からオゾンと空気の混合ガスを常圧で、オゾン濃度２０ｇ／Ｎｍ３で流量６００ｍＬ／分にて流し、室温で６時間、エバポレーターによりナスフラスコを回転させながら、反応させ、オゾン酸化処理したＳＧＣＮＴを得た。得られたＳＧＣＮＴについて、上記した方法でＢＥＴ比表面積を求め、また昇温脱離法による評価を行った。これらの結果を表１に示す。
[Oxidation treatment]
1 g of SGCNT synthesized above was put into a 500 mL eggplant flask and connected to an evaporator. While flowing a mixed gas of ozone and air from the ozone generator to the evaporator gas flow path at a normal pressure, an ozone concentration of 20 g / Nm 3 at a flow rate of 600 mL / min, and rotating the eggplant flask by the evaporator for 6 hours at room temperature. SGCNT which was made to react and was subjected to ozone oxidation treatment was obtained. About obtained SGCNT, the BET specific surface area was calculated | required by the above-mentioned method, and the evaluation by a temperature rising desorption method was performed. These results are shown in Table 1.
実施例１
上記でオゾン酸化処理したＳＧＣＮＴ１０ｍｇを、エチレングリコール（和光純薬工業製 特級）に加え、超音波ホモジナイザー（三井電気社製 ＵＸ−３００ ３００Ｗ ２０ｋＨｚ 循環冷却ユニット使用）で３０分間分散を行った。得られたＳＧＣＮＴ／エチレングリコール分散液に表１に示す所定の白金ナノ粒子担持率になるようＨ２ＰｔＣｌ６・Ｈ２Ｏ（和光純薬工業製特級）を加え、超音波を照射して溶解させた。その後１ｍｏｌ／ＬのＮａＯＨ／エチレングリコール溶液を加え、溶液のｐＨを１０とした。この溶液を三口フラスコ（２００ｍＬ）に移し、１４０℃で３時間、還流下反応させた。反応終了後、溶液を室温まで冷却し、水：エタノール＝１：１の混合液（体積比；以下、同様。）を３０ｍＬ加え、遠心分離を行った。この操作を６回繰り返した。このようにして、白金ナノ粒子担持ＳＧＣＮＴ溶液を得た。
Example 1
10 mg of SGCNT subjected to the ozone oxidation treatment as described above was added to ethylene glycol (special grade manufactured by Wako Pure Chemical Industries), and dispersion was performed for 30 minutes with an ultrasonic homogenizer (UX-300
上述のようにして調製した白金ナノ粒子担持ＳＧＣＮＴを０．１ｇ／Ｌとなるように水：エタノール＝１：１の混合液を加えた。さらにＳＧＣＮＴに対して質量比で０．６となるように、アイオノマーである１０％Ｎａｆｉｏｎ溶液（和光純薬工業株式会社製 ＤＥ１０２０）を加え、前述の超音波ホモジナイザーで１０分間分散処理を行い、ＳＧＣＮＴを含有するインクを調製した。調製したインクについて、触媒活性成分である白金ナノ粒子の担体ＣＮＴからの脱落を評価した。評価結果を表１に示す。 A mixture of water: ethanol = 1: 1 was added so that the platinum nanoparticle-supporting SGCNT prepared as described above was 0.1 g / L. Further, a 10% Nafion solution (DE1020 manufactured by Wako Pure Chemical Industries, Ltd.), which is an ionomer, is added so that the mass ratio is 0.6 with respect to SGCNT, and dispersion treatment is performed for 10 minutes with the above-described ultrasonic homogenizer. An ink containing was prepared. With respect to the prepared ink, the dropping of the platinum nanoparticles as the catalytically active component from the carrier CNT was evaluated. The evaluation results are shown in Table 1.
次いで、このインクをグラッシーカーボン棒（面積：０．１９６ｃｍ２）にパルススプレーにて所定量の量を塗布し、これを作用極として、触媒の電気化学的表面積（ＥＣＳＡ）を測定した。対極には多孔性ガラスフィルターで隔離された白金コイルを使用した。参照極には、ダブルジャンクション構造としたＨｇ／Ｈｇ２ＳＯ４／ｓａｔ−Ｋ２ＳＯ４を用いた。測定セルには、５つ口ガラス製セルを使用した。電解質として６０％過塩素酸（ナカライテスク株式会社和光純薬工業製 精密分析用 品番）をＭｉｌｌｉＱ水で０．１Ｍに調整したものを用いた。測定用ガスには純度９９．９９９９％のＮ２ガスを用いた。電気化学測定には電気化学測定システム（Ｓｏｌａｒｔｒｏｎ社製）を用い、回転電極装置としては、北斗電工株式会社製ＨＲ−２０１およびＨＲ−２０２を用いた。評価結果を表１に示す。 Next, a predetermined amount of this ink was applied to a glassy carbon rod (area: 0.196 cm 2 ) by pulse spraying, and using this as a working electrode, the electrochemical surface area (ECSA) of the catalyst was measured. A platinum coil separated by a porous glass filter was used as the counter electrode. As the reference electrode, Hg / Hg 2 SO 4 / sat-K 2 SO 4 having a double junction structure was used. A five-neck glass cell was used as the measurement cell. As the electrolyte, 60% perchloric acid (product number for precision analysis, manufactured by Nacalai Tesque Co., Ltd., Wako Pure Chemical Industries, Ltd.) adjusted to 0.1 M with MilliQ water was used. N 2 gas having a purity of 99.9999% was used as the measurement gas. An electrochemical measurement system (manufactured by Solartron) was used for electrochemical measurement, and HR-201 and HR-202 manufactured by Hokuto Denko Co., Ltd. were used as rotating electrode devices. The evaluation results are shown in Table 1.
比較例１
酸化処理を行っていないＳＧＣＮＴ（未処理ＳＧＣＮＴ）を用いた以外は、実施例１と同様にして各種評価を行った。これらの評価結果を表１に併記する。
Comparative Example 1
Various evaluations were performed in the same manner as in Example 1 except that SGCNT not subjected to oxidation treatment (untreated SGCNT) was used. These evaluation results are also shown in Table 1.
表１より、オゾン酸化処理を施したＳＧＣＮＴは、昇温脱離法における１５０〜９５０℃での一酸化炭素の脱離量および二酸化炭素の脱離量ならびに窒素ガス吸着によるＢＥＴ比表面積が適正に調整されていることがわかる。
また、このＳＧＣＮＴを担体ＣＮＴとして使用した実施例１では、分散処理における触媒活性成分の担体ＣＮＴからの脱落が見られず、また電気化学的表面積（ＥＣＳＡ）も比較例１に比べて大幅に増加しており、触媒活性成分の脱落が抑えられ、長期にわたって高い触媒活性を維持可能な酸化還元触媒が得られていることがわかる。
From Table 1, SGCNT subjected to ozone oxidation treatment has an appropriate desorption amount of carbon monoxide and desorption amount of carbon dioxide at 150 to 950 ° C. in the temperature programmed desorption method, and a BET specific surface area by nitrogen gas adsorption. You can see that it has been adjusted.
Further, in Example 1 in which this SGCNT was used as the carrier CNT, the catalytically active component was not dropped from the carrier CNT in the dispersion treatment, and the electrochemical surface area (ECSA) was also significantly increased compared to Comparative Example 1. Thus, it can be seen that the oxidation-reduction catalyst capable of maintaining the high catalytic activity over a long period of time is obtained, with the dropping of the catalytically active component suppressed.
１０ 光電極
１０ａ 光電極基板
１０ｂ 多孔質半導体微粒子層
１０ｃ 増感色素層
１０ｄ 支持体
１０ｅ 導電膜
２０ 電解質層
３０ 対向電極
３０ａ 支持体
３０ｂ 触媒層
３０ｃ 導電膜
５０ セパレータ
６０ 燃料電池用膜電極接合体（ＭＥＡ）
７０ 空気極
７０ａ カソード側拡散層
７０ｂ カソード側触媒層
８０ 電解質膜
９０ 燃料極
９０ａ アノード側拡散層
９０ｂ アノード側触媒層
DESCRIPTION OF
70
Claims (8)
A fuel cell comprising the membrane electrode assembly for a fuel cell according to claim 7.
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| JP2019006741A (en) * | 2017-06-28 | 2019-01-17 | 国立大学法人九州大学 | Metal complex, and fuel cell or solar cell employing the metal complex |
| KR20200028052A (en) * | 2018-09-05 | 2020-03-16 | 한국생산기술연구원 | Membrane electrode assembly for proton exchange membrane fuel cell and manufacturing method of catalyst for proton exchange membrane fuel cell |
| CN114824328A (en) * | 2022-05-12 | 2022-07-29 | 吉林大学 | Photosensitive low-temperature metal-air battery pack and preparation method thereof |
| JP2022117264A (en) * | 2021-01-29 | 2022-08-10 | 日本ゼオン株式会社 | Counter electrode for photoelectric conversion element, dye-sensitized solar cell and solar cell module |
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