Engstfeld Albert K, Klein Jens, Brimaud Sylvain
Institute of Surface Chemistry and Catalysis, Ulm University, Albert-Einstein-Allee 47, 89081, Ulm, Germany.
Present Address: Institute of Electrochemistry, Ulm University, Albert-Einstein-Allee 47, 89081, Ulm, Germany.
Chemphyschem. 2021 May 5;22(9):828-832. doi: 10.1002/cphc.202000979. Epub 2021 Apr 6.
The most prominent and intensively studied anode catalyst material for direct methanol oxidation fuel cells consists of a combination of platinum (Pt) and ruthenium (Ru). Classically, their high performance is attributed to a bifunctional reaction mechanism where Ru sites provide oxygen species at lower overpotential than Pt. In turn, they oxidize the adsorbed carbonaceous reaction intermediates at lower overpotential; among these, the Pt site-blocking carbon monoxide. We demonstrate that well-defined Pt modified Ru(0001) single crystal electrodes, with varying Pt contents and different local PtRu configurations at the surface, are unexpectedly inactive for the methanol oxidation reaction. This observation stands in contradiction with theoretical predictions and the concept of bifunctional catalysis for this reaction. Instead, we suggest that pure Pt defect sites play a more critical role than bifunctional defect sites on the electrodes investigated in this work.
用于直接甲醇氧化燃料电池的最突出且研究最深入的阳极催化剂材料是由铂（Pt）和钌（Ru）组合而成。传统上，它们的高性能归因于双功能反应机制，其中Ru位点比Pt以更低的过电位提供氧物种。相应地，它们在更低的过电位下氧化吸附的含碳反应中间体；其中，Pt位点会被一氧化碳阻断。我们证明，具有不同Pt含量和表面不同局部PtRu构型的明确定义的Pt修饰Ru(0001)单晶电极，对于甲醇氧化反应意外地没有活性。这一观察结果与理论预测以及该反应的双功能催化概念相矛盾。相反，我们认为在这项工作所研究的电极上，纯Pt缺陷位点比双功能缺陷位点起着更关键的作用。
