成果報告書詳細
管理番号20110000001109
タイトル*平成22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 次世代技術開発/シリカでの被覆を応用したPEFC用新規非Pt系カソード触媒の開発
公開日2011/10/12
報告書年度2010 - 2010
委託先名国立大学法人九州大学
プロジェクト番号P10001
部署名新エネルギー部
和文要約和文要約等以下本編抜粋:1. 研究開発の内容および成果等 (1) シリカ被覆カーボンナノチューブ担持Pt触媒のシリカ層厚さと酸素還元活性の関係 現行の固体高分子形燃料電池(PEFC)では、アノード、カソード共に炭素担持Pt触媒が利用されているが、カソードのPt触媒は酸性、高い正電位、酸素雰囲気などの厳しい条件にさらされるため、Pt粒子同士の凝集、Ptの溶解~再析出によるPt粒子径成長によりPt触媒の活性が低下する。
英文要約Title: Development of Non-Pt Cathode Catalysts for PEFC by Coverage with Silica Layers (FY2010-FY2011) FY2010 Annual Report
1. Evaluation of catalytic activity of carbon nanotube-supported Pt catalysts covered with silica layers of different thickness
We have reported that the durability of carbon nanotube-supported Pt cathode catalysts (Pt/CNT) in polymer electrolyte fuel cells (PEFCs) was improved by coverage with silica layers. In this study, we evaluated the catalytic activity of silica-coated Pt/CNT for the oxygen reduction. Thickness of silica layers which were wrapped around Pt/CNT was controlled to be 3 or 5 nm. The durability of silica-coated Pt/CNT was investigated by the potential cycling between 0.05 and 1.20 V (vs. RHE). The durability of silica-coated Pt/CNT became higher as silica layers in the catalysts were thicker. The reaction rate of the oxygen reduction over silica-coated Pt/CNT became lower with thickness of silica layers. This result suggests that the silica layers which were wrapped around Pt metal particles impede the diffusion of oxygen molecules during the oxygen reduction over silica-coated Pt/CNT. The Pt/CNT covered with silica layers of 3 nm thickness showed a similar activity for the oxygen reduction to Pt/CNT. Thus, the Pt/CNT covered with silica layers of 3 nm thickness is effective for the cathode catalysts in PEFCs.
2. Evaluation of the durability and activity of silica-coated Pd/CNT
It is well known that Pd metal shows high activity for the oxygen reduction, but Pd metal easily dissolves under PEFC cathode conditions. We have reported that the coverage of Pd/CNT with silica layers improves the durability of Pd metal under the PEFC cathode conditions. In the present study, we evaluated the effect of silica layer thickness in silica-coated Pd/CNT on the catalytic activity for the oxygen reduction and the durability under the cathode conditions. The Pd/CNT was covered with silica layers of 1, 3 and 5 nm thickness. Pd/CNT and silica-coated Pd/CNT with silica layers of 1 nm thickness were seriously deactivated due to the dissolution of Pd metal during the potential cycling experiment between 0.05 and 1.20 V. In contrast, the coverage of Pd/CNT with silica layers thicker than 3 nm inhibited the dissolution of Pd species out of the silica layers during the potential cycling experiment. The catalytic activity of Pd/CNT for the oxygen reduction reaction was decreased by the coverage with thicker silica layers. However, the decrease in the catalytic activity of Pd/CNT by coverage with silica layers of 3 nm thickness was insignificant. Thus, Pd/CNT covered with silica layers of 3 nm thickness showed high activity and excellent durability for the oxygen reduction under PEFC cathode conditions.
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