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.