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

Electrochemical CO 2 reduction in acidic electrolyte is a potential strategy for efficient CO 2 utilization by preventing the formation of carbonate, but it remains a great challenge to improve the selectivity of CO 2 reduction in acidic electrolytes due to the competitive hydrogen evolution reaction . Herein, we demonstrate Ag 2 CrO 4 derived Ag–Cr 2 O 3 composite catalyst with local alkaline microenvironments for enhanced selectivity of CO 2 to CO product in an acidic KCl electrolyte. Under the electrochemical reduction of CO 2 , the Ag 2 CrO 4 pre-catalyst undergoes a chemical transformation induced by chloride ions to generate AgCl–Cr 2 O 3 , meanwhile, AgCl is electrochemically reduced Ag to form a Cr 2 O 3 coated Ag composite catalyst with rich Ag–Cr 2 O 3 interfaces. The Ag–Cr 2 O 3 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 Cr 2 O 3 can adsorb OH − which regulates the local alkaline environment to promote the CO 2 adsorption on the Ag–Cr 2 O 3 interface and stabilize the *CO 2 - /*COOH intermediates in the acidic electrolyte. This work provides an effective strategy to tune the reaction interfaces for CO 2 reduction in acidic electrolytes.