Efficient CO ₂ Electroreduction to C _{2 <b>+</b>} Products on Hydroxide-Metal Catalysts via Enhanced Asymmetric C–C coupling

Electrochemical CO 2 reduction reaction (CO 2 RR) on copper-based catalysts offers a viable route to convert CO 2 into multicarbon (C 2+ ) 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 C 2+ Faradaic efficiency (FE) of 81.4% at 400 mA cm –2 in the flow cell. In a membrane electrode assembly (MEA), it delivers a C 2 H 4 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 CO 2 RR 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 C 2+ 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 CO 2 RR selectivity toward C 2+ species.