An in situ exsolved Cu-based electrocatalyst from an intermetallic Cu 5 Si compound for efficient CH 4 electrosynthesis.

A Cu-based electrocatalyst ( e -Cu 5 Si) is developed by in situ exsolving ultrathin SiO x layer-coated CuO/Cu nanoparticles (<100 nm) on the surface of a conductive intermetallic Cu 5 Si parent. This specially designed e -Cu 5 Si catalyst exhibits high performance for the CO 2 reduction reaction (CO 2 RR), which affords an excellent CH 4 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 SiO x layer, CuO/Cu species, and substrate contribute to fast interfacial electron transfer for the CO 2 RR. Moreover, in situ Raman analysis suggests that the ultrathin SiO x layer simultaneously stabilizes the active Cu 1+ species and promotes the protonation of *CO to form *CH x O, thereby greatly improving overall selectivity and activity of CH 4 production.