Spontaneous water dissociation on intermetallic electride LaCu0.67Si1.33 enhances electrochemical methanization of CO2
Luming Zhang, Huan Ma, Yongfang Sun, Yilin Zhao, Huiying Deng, Yuhang Wang, Fei Wang, Xiaodong Wen, Mingchuan Luo
Abstract
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 LaCu0.67Si1.33 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. Water dissociation has proven power in tuning the behaviors of electrochemical CO2 reduction. Here, the authors report the spontaneous water dissociation capability of the intermetallic electride LaCu0.67Si1.33 material that enables high rate electrosynthesis of methane from CO2.