Spontaneous water dissociation on intermetallic electride LaCu<sub>0.67</sub>Si<sub>1.33</sub> enhances electrochemical methanization of CO<sub>2</sub>.

Zhang, Luming; Ma, Huan; Sun, Yongfang; Zhao, Yilin; Deng, Huiying; Wang, Yuhang; Wang, Fei; Wen, Xiao-Dong et al. · Nat Commun · 2025

basic_science · Level V

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Abstract

Renewable electricity driven CO<sub>2</sub> 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 CO<sub>2</sub>. Combinative experimental and theoretical approaches strongly evidence a spontaneous WD on an IE LaCu<sub>0.67</sub>Si<sub>1.33</sub> 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<sup>-2</sup> 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 CO<sub>2</sub>.