Efficient CO₂ Electroreduction to C₂₊ Products on Hydroxide-Metal Catalysts via Enhanced Asymmetric C–C coupling

Electrochemical CO2 reduction reaction (CO2RR) on copper-based catalysts offers a viable route to convert CO2 into multicarbon (C2+) products, yet its selectivity is often constrained by insufficient *CO surface coverage and sluggish C–C coupling kinetics. Herein, we report a hybrid europium hydroxide-modified copper catalyst (Eu(OH)3-Cu) that enhances *CO affinity and C–C coupling efficiency. The catalyst achieves a C2+ Faradaic efficiency (FE) of 81.4% at 400 mA cm–2 in the flow cell. In a membrane electrode assembly (MEA), it delivers a C2H4 FE of 55.7% at 300 mA cm–2, with a full-cell energy efficiency of 21.4%. In situ electrochemical and spectroscopic analyses reveal that Eu(OH)3-Cu-5% lowers the CO2RR onset potential while stabilizing *CO and *OCCHO intermediates. Density functional theory (DFT) calculations further indicate that the Eu(OH)3 decoration strengthens *CO adsorption at the hydroxide-metal interface, promotes *CO protonation to *CHO, and facilitates asymmetric *CO-*CHO coupling, collectively leading to enhanced C2+ product formation. These findings demonstrate rare earth hydroxide-metal interface engineering as an effective strategy to enhance *CO coverage, improve coupling kinetics, and steer the CO2RR selectivity toward C2+ species.