Collaborative Innovation Center of Chemistry for Energy Materials, State Key Laboratory for Physical Chemistry of Solid Surface, Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China.
Phys Chem Chem Phys. 2019 Dec 7;21(45):25047-25053. doi: 10.1039/c9cp04346b. Epub 2019 Nov 6.
As an important pathway for energy storage and a key reaction in the carbon cycle, the CO electrochemical reduction reaction has recently gained significant interest. A variety of catalysts have been used to approach this topic experimentally and theoretically; however, the molecular level insight into the reaction mechanism is lacking due to the complexity of the surface processes and the challenges in probing the intermediate species. In this study, CO reduction reactions on polycrystalline Cu and Au electrodes were investigated in 0.1 M CO-saturated NaHCO solution. In situ sum frequency generation (SFG) spectroscopy has been adopted to access the intermediates and products on the metal electrodes. On the Au electrode, only linearly adsorbed CO could be detected, and the reduction produced no hydrocarbon species. On the Cu electrode, C-H stretching vibrations corresponding to surface-adsorbed ethoxy species were observed, but no CO vibrations can be detected with SFG. The results revealed that the CO randomly adsorbed on the Cu surface, and the multiple orientations of the adsorbed species may be the reason for the formation of C-C bonding. These results demonstrate direct molecular level evidence for different reaction pathways on the Cu and Au electrodes.
作为能量存储的重要途径和碳循环中的关键反应，CO 的电化学还原反应最近引起了广泛关注。已经使用了各种催化剂来从实验和理论上研究这个课题；然而，由于表面过程的复杂性和探测中间物种的挑战，对反应机制的分子水平洞察力仍然缺乏。在这项研究中，在 0.1 M CO 饱和的 NaHCO 溶液中研究了多晶 Cu 和 Au 电极上的 CO 还原反应。采用原位和频发生（SFG）光谱法来探测金属电极上的中间体和产物。在 Au 电极上，只能检测到线性吸附的 CO，并且还原没有产生碳氢化合物。在 Cu 电极上，观察到对应于表面吸附乙氧基物种的 C-H 伸缩振动，但 SFG 无法检测到 CO 振动。结果表明，CO 在 Cu 表面随机吸附，吸附物种的多个取向可能是形成 C-C 键的原因。这些结果证明了 Cu 和 Au 电极上不同反应途径的直接分子水平证据。
