The Role of Undercoordinated Sites on Zinc Electrodes for CO2 Reduction to CO

The electrochemical CO2 reduction reaction (CO2RR) using renewable energies is a promising route toward global carbon neutrality. Recently, the use of copper catalysts and CO feedstocks, instead of CO2, has been shown to enhance the selectivity toward multicarbon products, leading to increased efforts in developing tandem electrocatalytic systems. State-of-the-art CO2-to-CO electrocatalysts are mainly based on noble metals such as silver and gold. Earth-abundant zinc, in contrast, displays poorer selectivity and activity. Herein, the use of porous dendritic oxidederived zinc (OD-Zn) catalysts for CO2RR is reported. These catalysts can reduce CO2 to CO with a maximum Faradaic efficiency of 86% at -0.95 V versus reversible hydrogen electrode (RHE) and partial current density of -266 mA cm(-2) at -1.00 V vs RHE. OD-Zn is further found to have a higher amount of undercoordinated sites and exhibits higher CO2RR activity and CO selectivity than electrodeposited Zn metal. While oxygen vacancies have been previously implicated as active sites, detailed experiments and density functional theory calculations show that Zn sites with a high degree of undercoordination provide even higher activity, in view of their nearly optimal *COOH adsorption energies. These findings showcase Zn-Oderived particles with plentiful undercoordinated sites as cost-effective electrocatalysts for CO production.