Electron Localization-Triggered Proton Pumping Toward Cu Single Atoms for Electrochemical CO 2 Methanation of Unprecedented Selectivity.

Slow multi-proton coupled electron transfer kinetics and unexpected desorption of intermediates severely hinder the selectivity of CO 2 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 CH 4 electrosynthesis over Cu single atoms anchored on bismuth vacancies of BiVO 4 (Bi 1-x VO 4 ─Cu), with superior kinetic isotope effect and high CH 4 Faraday efficiency (92%), far outperforming state-of-the-art electrocatalysts for CO 2 methanation. Control experiments and theoretical calculations reveal that the bismuth vacancies (V Bi ) not only act as active sites for H 2 O 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 CH 4 electrosynthesis. The metal vacancies as new initiators show enormous potential in the proton transfer-involved hydrogenative conversion processes.