Facet Engineering of Cu2O–Ag Heterostructures for Promoting CO Generation in Electrocatalytic CO2 Reduction

Abstract The electrocatalytic reduction of carbon dioxide (CO2RR) into high-value-added and high-energy-density multicarbon (C2+) products hold great significance for sustainable energy conversion and carbon neutrality. However, achieving high product selectivity toward C2+ products presents a major challenge due to the complex multielectron transfer and competitive reaction pathways involved in the CO2RR process. In this work, Cu2O nanoparticles with distinct exposed crystal facets were synthesized and employed to construct Cu2O–Ag nanoheterojunction electrocatalysts. Through rational modulation of the crystal-plane orientation and heterojunction structure, highly selective and efficient electrocatalytic conversion of CO2 to C2+ products was achieved. In a gas-diffusion flow electrolytic cell, the optimized catalyst delivered a maximum Faradaic efficiency of 77.6% for C2+ products at –1.0 V vs the reversible hydrogen electrode (RHE), accompanied by a current density of 300 mA cm–2. The catalytic mechanism was further investigated through in situ Raman spectroscopy combined with density functional theory calculations. The results demonstrate that Cu2O–Ag heterostructures enable efficient tandem CO2RR by regulating the balance between *CO generation and utilization. Ag nanoparticles serve as efficient CO-generating sites, while the exposed Cu crystal facets and Cu–Ag interfaces determine the adsorption configuration and subsequent coupling of CO intermediates. This synergistic interaction promotes CO dimerization and facilitates C–C coupling toward C2+ products.