<i>In Situ</i> Infrared Spectroscopic Evidence of Enhanced Electrochemical CO<sub>2</sub> Reduction and C–C Coupling on Oxide-Derived Copper
Ernest Pahuyo Delmo, Yian Wang, Yihua Song, Shangqian Zhu, Haichuan Zhang, Hongming Xu, Tiehuai Li, Juhee Jang, Yongjun Kwon, Yinuo Wang, Minhua Shao
Abstract
The reaction mechanism of CO 2 electroreduction on oxide-derived copper has not yet been unraveled even though high C 2+ Faradaic efficiencies are commonly observed on these surfaces. In this study, we aim to explore the effects of copper anodization on the adsorption of various CO 2 RR intermediates using in situ surface-enhanced infrared absorption spectroscopy (SEIRAS) on metallic and mildly anodized copper thin films. The in situ SEIRAS results show that the preoxidation process can significantly improve the overall CO 2 reduction activity by (1) enhancing CO 2 activation, (2) increasing CO uptake, and (3) promoting C–C coupling. First, the strong *COO – redshift indicates that the preoxidation process significantly enhances the first elementary step of CO 2 adsorption and activation. The rapid uptake of adsorbed *CO atop also illustrates how a high *CO coverage can be achieved in oxide-derived copper electrocatalysts. Finally, for the first time, we observed the formation of the *COCHO dimer on the anodized copper thin film. Using DFT calculations, we show how the presence of subsurface oxygen within the Cu lattice can improve the thermodynamics of C 2 product formation via the coupling of adsorbed *CO and *CHO intermediates. This study advances our understanding of the role of surface and subsurface conditions in improving the catalytic reaction kinetics and product selectivity of CO 2 reduction.