An in situ exsolved Cu-based electrocatalyst from an intermetallic Cu₅Si compound for efficient CH₄ electrosynthesis

A Cu-based electrocatalyst (e-Cu5Si) is developed by in situ exsolving ultrathin SiOx layer-coated CuO/Cu nanoparticles (<100 nm) on the surface of a conductive intermetallic Cu5Si parent. This specially designed e-Cu5Si catalyst exhibits high performance for the CO2 reduction reaction (CO2RR), which affords an excellent CH4 faradaic efficiency (FE) of 49.0% with partial current density of over 140.1 mA cm(-2) at -1.2 V versus reversible hydrogen electrode (RHE) in a flow cell, with outstanding stability. The strongly coupled multiphase interfaces among the SiOx layer, CuO/Cu species, and substrate contribute to fast interfacial electron transfer for the CO2RR. Moreover, in situ Raman analysis suggests that the ultrathin SiOx layer simultaneously stabilizes the active Cu1+ species and promotes the protonation of *CO to form *CHxO, thereby greatly improving overall selectivity and activity of CH4 production.