Synergistic Electronic Modulation in Dual-Alkali-Doped CuO for Wide-Window CO2 to C2 Electroreduction

Abstract

Electrocatalytic CO2 reduction (CO2ER) to C2 products on Cu-based catalysts is often limited by poor selectivity, narrow potential windows, and competitive hydrogen evolution (HER). Here, a bulk lattice co-doping strategy involving dual alkali metals (Na and K) is developed by modulating the Cu coordination environment. This approach synergistically regulates the intrinsic electronic structure of the catalyst to enhance CO2 adsorption and lower the C–C bond coupling energy barrier. The bulk-phase Na and K co-doped CuO delivers a Faradaic efficiency for C2 (FEC2) of 73.6% and a partial C2 current density of –286.9 mA cm−2 specifically at –1.8 V vs RHE, while maintaining FEC2 > 60% across a wide potential window (–1.2 to –2.4 V vs RHE). Experimental results and mechanistic investigations demonstrate that the introduction of K increases the electron density of the surrounding Cu species, thereby enhancing CO2 adsorption and suppressing HER. Meanwhile, the incorporation of Na effectively lowers the energy barrier for the asymmetric *CO–*CHO coupling. This dual alkali metal co-doping strategy significantly promotes the electrochemical reduction of CO2 toward C2 products. This work establishes bulk alkali metal doping as a viable strategy for designing high-performance, wide potential window CO2ER catalysts.