Self-Supported CuO/Bi Heterostructure for Electroreduction of CO2 to Formate by Synergistic Electronic Effects

Abstract

Tuning product distribution in CO2 electroreduction (CO2RR) using Cu-Bi based bimetallic catalysts is a key strategy for enhancing selectivity and reaction kinetics. Notably, self-supported bimetallic electrocatalysts derived from mesoporous Cu foam hold significant potential for achieving industrially relevant current densities for CO2RR. The CuO/Bi heterostructure on mesoporous Cu foam developed by a simple chemical oxidation cum electrodeposition resulted in selectively HCOO- generation with faradaic efficiency of 53% at -1.4 V versus RHE and current density of 84.5 mA cm-2 outperforming both CuO nanowires and Bi nanosheets. Further, it exhibits a remarkable HCOO- production rate of 648.0 mu mol h-1cm-2 with durability over 16 h. Density functional theory calculations reveal that the charge transfer and redistribution at the Cu/CuO/Bi interface facilitate the shift of band centers tuning the overpotential for better CO2 reduction. The reaction pathway analysis indicates that *OCHO intermediate is thermodynamically stable leading to HCOO- than *COOH (leading to CO). Tafel slopes, double layer capacitance, and activation barrier plots provide further insights into CO2RR kinetics, illustrating the electron transfer process and the selectivity. The study not only demonstrates construction of a low cost, efficient CuO/Bi based heterostructure, but offers valuable insights to the interface interactions that tunes the intermediates favoring HCOO- generation.