Interfacing CuO and Cu with Bi tailors the product distribution and the charge redistribution at the interface leads to a metallic nature and shifts p-d band centers favoring CO₂RR to formate.

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 µmol 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.