Manipulating local coordination of copper single atom catalyst enables efficient CO₂-to-CH₄ conversion.

Abstract

Electrochemical CO₂ conversion to methane, powered by intermittent renewable electricity, provides an entrancing opportunity to both store renewable electric energy and utilize emitted CO₂. Copper-based single atom catalysts are promising candidates to restrain C-C coupling, suggesting feasibility in further protonation of CO* to CHO* for methane production. In theoretical studies herein, we find that introducing boron atoms into the first coordination layer of Cu-N₄ motif facilitates the binding of CO* and CHO* intermediates, which favors the generation of methane. Accordingly, we employ a co-doping strategy to fabricate B-doped Cu-N_x atomic configuration (Cu-N_xB_y), where Cu-N₂B₂ is resolved to be the dominant site. Compared with Cu-N₄ motifs, as-synthesized B-doped Cu-N_x structure exhibits a superior performance towards methane production, showing a peak methane Faradaic efficiency of 73% at -1.46 V vs. RHE and a maximum methane partial current density of -462 mA cm^-2 at -1.94 V vs. RHE. Extensional calculations utilizing two-dimensional reaction phase diagram analysis together with barrier calculation help to gain more insights into the reaction mechanism of Cu-N₂B₂ coordination structure.