Direct electrochemical conversion of CO2 to ethanol offers a promising strategy to lower CO2 emissions while storing energy from renewable electricity. However, the high selectivity for producing ethanol using current electrocatalyst is rather difficult. Our recent study reported that a synthesized carbon-supported copper (Cu) catalyst achieves a single-product Faradic efficiency (FE) of 91% at -0.7 V and the onset potential as low as -0.4 V for ethanol. Furthermore, by carrying out operando X-ray absorption near edge structure (XANES), we found a transformation from atomically dispersed Cu to Cu clusters during the reaction. In order to gain further understanding of the dynamic evolution of the active site structure and its impact on CO2 reduction activity, a multiscale modeling approach combined density functional theory (DFT) calculations and theoretical XANES simulations were carried out to study the reaction mechanism and reveal the active site structures. Using the experimentally measured XANES as a guidance, we qualitatively reveal the structures of the pre, in-situ, and post catalyst with structure analysis of the theoretical XANES simulations, which confirms the transformation of the active site structure during the reaction. Based on the mechanistic study, we also evaluated the limiting potential of CO2 reduction as -0.41 V and identified the rate determining step as C-C bond formation. We also found out that the C-C bond formation energy barrier is size dependent, as cluster size increases, the energy barrier for C-C bond formation increases. Our computational results agree well with experimental investigation and validate our previous findings, which also provides guidance for future catalyst development.

Investigation of dynamics evolution of atomically dispersed Cu catalyst and its impact on CO2 reduction activity

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