Dual-Element Modulation of Cu Active Sites toward Enhanced C-C Coupling in CO2 Electroreduction

Abstract

Electrochemical CO2 reduction (eCO(2)R) on copper (Cu) offers a promising route for producing multicarbon (C2+) products but is limited by sluggish C-C coupling kinetics and competing hydrogen evolution. Here, we report a dual-element modulation strategy for directly engineering Cu active sites through the coincorporating boron (B) and gold (Au), yielding a heterostructured Au-B comodified Cu catalyst (AuBDCh-1) composed of hollow nanocage domains and residual dense nanoparticles. In flow-cell tests with 1 M KOH, AuBDCh-1 delivers a 3.21-fold higher C2+ partial current density (-270.0 +/- 26.7 mA cm(-2)@-500 mA cm(-2)) and a 2.24-fold improvement in cathodic energy efficiency (39.12 +/- 4.50%@-400 mA cm(-2)) compared with pristine Cu, while effectively suppressing competing hydrogen evolution and methane formation. The catalyst retains its activity in a 5 cm(2) membrane electrode assembly (MEA), achieving 51.6% C2+ selectivity and a C2+ partial current density of -154.7 mA cm(-2) at -300 mA cm(-2). In situ Raman spectroscopy reveals that AuBDCh-1 exhibits an increased *COatop/*CObridge ratio and a higher fraction of *COHFB, establishing a *CO adsorption environment favorable for C-C coupling. In addition, electrochemical CO reduction (eCOR) further confirms its enhanced C-C coupling capability with suppressed protonation to CH4. Density functional theory (DFT) calculations reveal that this dual modification strengthens *CO binding (-0.70 eV) and reduces the kinetic barrier for C-C bond formation (0.85 eV vs 0.99/1.07 eV for B-only/pristine Cu). Together, these results establish B-Au dual modulation as a robust and transferable design principle for advancing selective CO2-to-C2+ electrolysis.