Engineering Water Molecules Activation Center on Multisite Electrocatalysts for Enhanced CO₂ Methanation

The renewable energy-powered electrolytic reduction of carbon dioxide (CO₂) to methane (CH₄) using water as a reaction medium is one of the most promising paths to store intermittent renewable energy and address global energy and sustainability problems. However, the role of water in the electrolyte is often overlooked. In particular, the slow water dissociation kinetics limits the proton-feeding rate, which severely damages the selectivity and activity of the methanation process involving multiple electrons and protons transfer. Here, we present a novel tandem catalyst comprising Ir single-atom (Ir₁)-doped hybrid Cu₃N/Cu₂O multisite that operates efficiently in converting CO₂ to CH₄. Experimental and theoretical calculation results reveal that the Ir₁ facilitates water dissociation into proton and feeds to the hybrid Cu₃N/Cu₂O sites for the *CO protonation pathway toward *CHO. The catalyst displays a high Faradaic efficiency of 75% for CH₄ with a current density of 320 mA cm^-2 in the flow cell. This work provides a promising strategy for the rational design of high-efficiency multisite catalytic systems.