Heterostructure of ZnO Nanosheets/Zn with a Highly Enhanced Edge Surface for Efficient CO₂ Electrochemical Reduction to CO

Abstract

Electrochemical reduction of CO₂ to valuable chemicals or fuels is critical for closing the carbon cycle and preventing further deterioration of the environment. Here, we discover that by adopting the Zn foil as the substrate, a ZnO two-dimensional sheet array is in situ synthesized on the Zn foil by a facile hydrothermal method. The obtained ZnO sheet array/Zn foil exhibited an outstanding CO₂ reduction performance to CO, which showed the highest Faraday efficiency of 85% for CO at -2.0 V (vs Ag/AgCl) with a current density of 11.5 mA/cm² compared with the freestanding ZnO sheets and particles and excellent stability in the 0.1 M KHCO₃ electrolyte. The in situ vertical ZnO sheet array exposed with abundant exposed (11̅00) edge facets can accelerate the electron transfer and improve the number of active sites, which leads to the enhanced reduction performance. Alongside, the density functional theory simulation indicated that the vertical-grown ZnO sheet array possesses lower Gibbs free energy for the CO₂ activation, with a more exposed (11̅00) edge surface of ZnO.