Wang Hongsen, Abruña Héctor D
Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853-1301, United States.
J Am Chem Soc. 2023 Aug 23;145(33):18439-18446. doi: 10.1021/jacs.3c04785. Epub 2023 Aug 8.
OH adspecies are involved in numerous electrocatalytic reactions, such as CO, H, methanol, and ethanol oxidation and oxygen reduction reactions, as a reaction intermediate and/or reactant. In this work, we have, for the first time, identified the OH stretching band of OH adspecies on Pt, Ru, and Pt/Ru electrodes with surface-enhanced infrared absorption spectroscopy (SEIRAS) in a flow cell through potential modulation and CO displacement. We found that while Ru had a relatively constant OH coverage at potentials between 0.1 and 0.8 V, Pt had a maximum OH coverage at 0.6 V in 0.1 M HClO and 0.7 V in 0.1 M KOH. CO oxidation kinetics on Ru were sluggish, although adsorbed OH appeared on Ru at very low potentials. Binary Pt/Ru electrodes promote CO oxidation through a synergistic effect in which Ru promotes OH adsorption and Pt catalyzes the reaction between the CO and OH adspecies. In addition, water coadsorbed with CO at Ru sites of Pt/Ru also plays an important role. These new spectroscopic results about OH adspecies could advance the understanding of the mechanism of fuel cell related electrocatalysis.
羟基吸附物种作为反应中间体和/或反应物参与众多电催化反应，如一氧化碳、氢气、甲醇和乙醇氧化以及氧还原反应。在这项工作中，我们首次通过电位调制和一氧化碳置换，利用流动池中表面增强红外吸收光谱（SEIRAS）在铂、钌和铂/钌电极上识别出了羟基吸附物种的羟基伸缩振动带。我们发现，虽然在0.1至0.8伏的电位范围内钌的羟基覆盖度相对恒定，但在0.1 M高氯酸中铂在0.6伏时具有最大羟基覆盖度，在0.1 M氢氧化钾中则在0.7伏时具有最大羟基覆盖度。尽管在非常低的电位下钌上出现了吸附的羟基，但钌上的一氧化碳氧化动力学较为迟缓。二元铂/钌电极通过协同效应促进一氧化碳氧化，其中钌促进羟基吸附，铂催化一氧化碳与羟基吸附物种之间的反应。此外，在铂/钌的钌位点上与一氧化碳共吸附的水也起着重要作用。这些关于羟基吸附物种的新光谱结果可能会促进对燃料电池相关电催化机理的理解。
