Department of Applied Chemistry, The University of Tokyo , 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.
Biofunctional Catalyst Research Team, Center for Sustainable Resource Science, RIKEN , 2-1, Hirosawa, Wako, Saitama 351-0198, Japan.
Langmuir. 2017 Sep 19;33(37):9307-9313. doi: 10.1021/acs.langmuir.7b00696. Epub 2017 May 8.
Understanding the competition between hydrogen evolution and CO reduction is of fundamental importance to increase the faradaic efficiency for electrocatalytic CO reduction in aqueous electrolytes. Here, by using a copper rotating disc electrode, we find that the major hydrogen evolution pathway competing with CO reduction is water reduction, even in a relatively acidic electrolyte (pH 2.5). The mass-transport-limited reduction of protons takes place at potentials for which there is no significant competition with CO reduction. This selective inhibitory effect of CO on water reduction, as well as the difference in onset potential even after correction for local pH changes, highlights the importance of differentiating between water reduction and proton reduction pathways for hydrogen evolution. In-situ FTIR spectroscopy indicates that the adsorbed CO formed during CO reduction is the primary intermediate responsible for inhibiting the water reduction process, which may be one of the main mechanisms by which copper maintains a high faradaic efficiency for CO reduction in neutral media.
了解析氢反应和 CO 还原反应之间的竞争对于提高水相电解液中电催化 CO 还原的法拉第效率至关重要。在这里，我们通过使用铜旋转圆盘电极发现，与 CO 还原竞争的主要氢析出途径是水还原，即使在相对酸性的电解液（pH 2.5）中也是如此。在没有与 CO 还原发生显著竞争的电位下，质子的传质限制还原发生。CO 对水还原的这种选择性抑制作用，以及即使在局部 pH 变化校正后起始电位的差异，凸显了区分水还原和质子还原途径对于析氢反应的重要性。原位傅里叶变换红外光谱表明，在 CO 还原过程中形成的吸附 CO 是抑制水还原过程的主要中间体，这可能是铜在中性介质中保持高 CO 还原法拉第效率的主要机制之一。
