Ag–Cr2O3 interfaces with local alkaline microenvironments for electroreduction of CO2 to CO in an acidic electrolyte

Abstract

Electrochemical CO2 reduction in acidic electrolyte is a potential strategy for efficient CO2 utilization by preventing the formation of carbonate, but it remains a great challenge to improve the selectivity of CO2 reduction in acidic electrolytes due to the competitive hydrogen evolution reaction. Herein, we demonstrate Ag2CrO4 derived Ag–Cr2O3 composite catalyst with local alkaline microenvironments for enhanced selectivity of CO2 to CO product in an acidic KCl electrolyte. Under the electrochemical reduction of CO2, the Ag2CrO4 pre-catalyst undergoes a chemical transformation induced by chloride ions to generate AgCl–Cr2O3, meanwhile, AgCl is electrochemically reduced Ag to form a Cr2O3 coated Ag composite catalyst with rich Ag–Cr2O3 interfaces. The Ag–Cr2O3 gas diffusion electrode constructed from carbon nanopowder effectively increases the hydrophobicity of the electrode, and the optimized electrode exhibits high CO Faradaic efficiency (FE) (over 75%) at a wide current density of 50–300 mA cm-2 and achieves a maximum FE of 86.7% toward CO product at 300 mA cm-2. The in situ Raman spectroscopy reveals that Cr2O3 can adsorb OH− which regulates the local alkaline environment to promote the CO2 adsorption on the Ag–Cr2O3 interface and stabilize the *CO2-/*COOH intermediates in the acidic electrolyte. This work provides an effective strategy to tune the reaction interfaces for CO2 reduction in acidic electrolytes.