Unraveling and tuning the linear correlation between CH4 and C2 production rates in CO2 electroreduction

Although many catalysts have been reported for the CO 2 electroreduction to C 1 or C 2 chemicals, the insufficient understanding of fundamental correlations among different products still hinders the development of universal catalyst design strategies. Herein, we first discover that the surface *CO coverage is stable over a wide potential range and reveal a linear correlation between the partial current densities of CH 4 and C 2 products in this potential range, also supported by the theoretical kinetic analysis. Based on the mechanism that *CHO is the common intermediate in the formation of both CH 4 (*CHO → CH 4 ) and C 2 (*CHO + *CO → C 2 ), we then unravel that this linear correlation is universal and the slope can be varied by tuning the surface *H or *CO coverage to promote the selectivity of CH 4 or C 2 products, respectively. As proofs-of-concept, using carbon-coated Cu particles, the surface *H coverage can be increased to enhance CH 4 production, presenting a high CO 2 -to-CH 4 Faradaic efficiency ( FE CH 4 ∼52%) and an outstanding CH 4 partial current density of –337 mA cm −2 . On the other hand, using an Ag-doped Cu catalyst, the CO 2 RR selectivity is switched to the C 2 pathway, with a substantially promoted FE C 2 of 79% and a high partial current density of –421 mA cm −2 . Our discovery of tuning intermediate coverages suggests a powerful catalyst design strategy for different CO 2 electroreduction pathways.