Active Sites of Zn Catalysts for CO2 Electroreduction to CO

Electrochemical CO2 reduction reaction (CO2RR) is an attractive strategy to mitigate CO2 emissions and enable the conversion of CO2 to valuable fuels. To date, noble metals, such as Ag, Au and Pd, have been reported as the benchmarking electrocatalysts to selectively convert CO2 to CO, but their scarcity and the associated high cost inevitably limit their large-scale applications. Zn holds the promise as a potential alternative to noble metals due to its earth-abundance and intrinsic selectivity for CO production. However, systematic studies that clarify the active sites of Zn catalysts for CO2RR are presently lacking in the literature. In response, density functional theory (DFT) calculations were used in this study to identify the active sites for CO2RR to CO based on a Zn50 model. The binding energies of the key intermediates for CO2RR and the competitive hydrogen evolution reaction (HER) on Zn(100) facet, Zn(002) facet, edge and corner sites were calculated. The Gibbs free energy diagrams for CO2RR and HER were then constructed based on the computational hydrogen electrode model. The results of this work that can guide further experiments to achieve highly efficient CO2RR over Zn-based catalysts.