Ga doping disrupts C-C coupling and promotes methane electroproduction on CuAl catalysts

The electrochemical CO2 reduction reaction (CO2RR) provides a route to store intermittent electricity in the form of fuels like methane. We reasoned that disrupting C-C coupling while maintaining high ∗CO coverage could enhance methane selectivity and suppress the hydrogen evolution reaction (HER). We studied the effect of doping CuAl, a material at the top of the CO2RR activity and selectivity volcano plot, with elements having low ∗CO binding energies: Au, Zn, and Ga. Encouraged by initial improvements in selectivity to methane, we optimized the Ga content and showed that the presence of uniformly dispersed Ga is crucial in CO2RR-to-methane performance enhancement. We rule out porosity and roughness and conclude that the presence of Ga in the doped catalysts enables high methane selectivity. The Ga-doped CuAl catalysts achieve a methane Faradaic efficiency (FE) of 53% by suppressing HER to 23% in neutral electrolyte at −1.4 V versus reversible hydrogen electrode.