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

Although many catalysts have been reported for the CO₂ electroreduction to C₁ or C₂ 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 CH₄ and C₂ 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 CH₄ (*CHO → CH₄) and C₂ (*CHO + *CO → C₂), 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 CH₄ or C₂ products, respectively. As proofs-of-concept, using carbon-coated Cu particles, the surface *H coverage can be increased to enhance CH₄ production, presenting a high CO₂-to-CH₄ Faradaic efficiency ( [Formula: see text] ∼52%) and an outstanding CH₄ partial current density of -337 mA cm^-2. On the other hand, using an Ag-doped Cu catalyst, the CO₂RR selectivity is switched to the C₂ pathway, with a substantially promoted [Formula: see text] 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 CO₂ electroreduction pathways.