Electron Localization‐Triggered Proton Pumping Toward Cu Single Atoms for Electrochemical CO2 Methanation of Unprecedented Selectivity

Slow multi-proton coupled electron transfer kinetics and unexpected desorption of intermediates severely hinder the selectivity of CO₂ methanation. In this work, a one-stone-two-bird strategy of pumping protons and improving adsorption configuration/capability enabled by electron localization is developed to be highly efficient for CH₄ electrosynthesis over Cu single atoms anchored on bismuth vacancies of BiVO₄ (Bi_1-xVO₄─Cu), with superior kinetic isotope effect and high CH₄ Faraday efficiency (92%), far outperforming state-of-the-art electrocatalysts for CO₂ methanation. Control experiments and theoretical calculations reveal that the bismuth vacancies (V_Bi) not only act as active sites for H₂O dissociation but also induce electron transfer toward Cu single-atom sites. The V_Bi-induced electron localization pumps *H from V_Bi sites to Cu single atoms, significantly promoting the generation and stabilization of the pivotal intermediate (*CHO) for highly selective CH₄ electrosynthesis. The metal vacancies as new initiators show enormous potential in the proton transfer-involved hydrogenative conversion processes.