Spontaneous water dissociation on intermetallic electride LaCu0.67Si1.33 enhances electrochemical methanization of CO2

Renewable electricity driven CO₂ electroreduction into methane offers a sustainable route to mitigate our dependence on natural gas. However, this route is now limited by the unsatisfied efficiency and short durability, which originates from a kinetic disparity between water dissociation (WD) and proton-coupled electron transfer on existing catalysts. Herein, we harness the exceptional WD capability of the intermetallic electride (IE) materials for the electrocatalytic methanization from CO₂. Combinative experimental and theoretical approaches strongly evidence a spontaneous WD on an IE LaCu_0.67Si_1.33 catalyst due to its unique electronic structure (strongly modified charge states, reversible lattice hydride ions and anionic electrons). Consequently, this catalyst exhibits improved methanization performance in alkaline flow cells, achieving a methane Faraday efficiency of 72% at -1.21 V versus the reversible hydrogen electrode (vs. RHE) and peak partial current density of 476.7 mA cm^-2 at -1.52 V vs. RHE. Energetic calculations further establish the mechanistic link between WD and methanization processes on our catalyst, on which a lowered free energy barrier for the key *CO to *CHO transformation step is observed. This work sheds light on the pivotal role of WD and expands the repertoire of materials for efficient electrocatalytic methanization from CO₂.