成果報告書詳細
管理番号20160000000156
タイトル*平成25年度中間年報 固体高分子形燃料電池実用化推進技術開発 基盤技術開発 カーボンアロイ触媒
公開日2016/5/28
報告書年度2013 - 2013
委託先名国立大学法人東京工業大学 国立大学法人東京大学 国立大学法人筑波大学 東レ株式会社 旭化成ケミカルズ株式会社 帝人株式会社 東芝燃料電池システム株式会社
プロジェクト番号P10001
部署名新エネルギー部
和文要約
英文要約Title: Carbon Alloy Catalyst Project (FY2010-FY2014) FY2013Annual Report

The polymer electrolyte fuel cell (PEFC) is a promising, clean power source for transportation and residential applications with high efficiency, low operating temperature, and reduced CO2 emissions. Considerable effort has been devoted to the solution of various problems associated with current fuel cell cathode electrocatalysts. Conventionally, platinum is used as a cathode electrocatalyst for the slow oxygen reduction reaction (ORR), but it is too expensive to provide a viable alternative to conventional energy sources. For practical use of PEFCs, alternative low-cost, platinum-free cathode catalysts with high power loads are necessary.
Carbon based materials doped with nitrogen are receiving much attention as catalysts, owing to their relatively high ORR activities. We have also been developing our own electrochemically active nitrogen-containing carbon materials. Our carbon catalyst materials are prepared by pyrolysing (heat treating) mixtures of nitrogen-containing polymers and metal complexes, rather than using metal complexes loaded onto a carbon support surface. Our approach could result in high density of active sites and greater durability of the resulting catalysts, since the chemical structure of the active sites is produced both in the bulk and on the surface of the carbon. These inexpensive, carbon-based catalysts, containing hetero-atoms such as boron or nitrogen, are known as carbon alloy catalysts (CACs). 
The finely divided power of CAC shows an improvement of ORR activity and also an improvement of air diffusion in cathode layer of MEA. The activation overpotential reduces with increasing of the amount of the catalyst. It is concluded that our new catalyst shows excellent catalytic activity and durability in real fuel cell conditions. The maximum output (0.56 V at 1.0 A cm-2 at 80°C and 0.2 MPa, H2?O2 gas) is better than the previous our cathode catalysts. It is difficult to conclude with the present data whether transition metal species are involved as catalytically active sites for ORR. However, this study provides a breakthrough in terms of methodology for preparation of highly active and highly stable ORR catalysts. The general understanding of this class of materials is that there is a trade-off between catalytic activity and durability. From the results of the electrochemical analysis and fuel cell test, ORR process of CAC consists two (O2 -> H2O2) and two (H2O2 -> H2O) electrons reductions. Also model catalyst of CAC was prepared, where the nitrogen atoms are selectively doped at the edge of graphite and nitrogen density is controlled by the edge density on the surface of graphite. We have then start to examine the ORR activity of model catalysts to clarify the ORR active site of the carbon alloy catalyst. Further research is required to improve catalytic activity and durability, and clarify the catalytically active center for precious-metal-free ORR catalysts.
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