The nature of active centers catalyzing oxygen electro-reduction at platinum surfaces in alkaline media
The nature of active centers catalyzing oxygen electro-reduction at platinum surfaces in alkaline media
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DOI：
10.1039/c8ee03228a
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发表时间：
2019-01-01
影响因子：
32.5
通讯作者：
Bandarenka, Aliaksandr S.
中科院分区：
文献类型：
--
作者：
Liang, Yunchang;McLaughlin, David;Bandarenka, Aliaksandr S.
随着近年来相关膜材料和系统的开发和商业化的实质性进展，使用OH传导电解质的能量转换装置变得越来越有吸引力。然而，在碱性介质中，许多催化剂对发生在这种装置的阴极处的氧电还原的活性令人惊讶地不同于在酸性电解质中的那些。这是例如Pt和Pt合金电极的情况，其表现出取决于电解质pH和表面结构的活性的意外和剧烈变化。在这里，我们应用最近推出的电化学扫描隧道显微镜噪声测量直接识别活性中心在Pt（111）为基础的表面在三种碱性电解质（LiOH，KOH和CsOH）的反应条件下。对于所有这三种解决方案，它被发现，最活跃的网站位于Pt（111）梯田，在酸性介质，凹缺陷显着增加氧还原活性相反。这些缺陷中心实际上在碱性介质中是失活的。这不仅解释了酸性和碱性电解质之间的上述活性差异，而且还提出了设计用于高pH值应用的纳米结构Pt电催化剂的策略。
Energy conversion devices that use OH-conducting electrolytes are becoming more and more attractive with recent substantial progress in the development and commercialization of relevant membrane materials and systems. However, the activities of numerous catalysts towards oxygen electro-reduction taking place at the cathodes of such devices in alkaline media are surprisingly different from those in acidic electrolytes. This is for instance the case for Pt and Pt-alloy electrodes, which demonstrate unexpected and drastic variations in activity depending on the electrolyte pH and surface structure. Here we apply recently introduced electrochemical scanning tunnelling microscopy noise measurements to directly identify active centers at Pt(111)-based surfaces in three alkaline electrolytes (LiOH, KOH and CsOH) under reaction conditions. For all three solutions it was found that the most active sites are located on the Pt(111) terraces, in contrast to the acidic media, where concave defects significantly increase the oxygen reduction activity. These defect-centers are to all practical purposes deactivated in alkaline media. This not only explains the above-mentioned activity differences between acidic and alkaline electrolytes but also suggests strategies to design nanostructured Pt-electrocatalysts for applications at high pH values.