Selective CO2 reduction to acetate via controlled sp2/sp3 carbon hybridization

Electrocatalytic reduction of CO2 to fuels and chemicals represents a promising pathway for CO2 utilization and energy conversion. However, metal-based catalysts often suffer from diminished selectivity in the direct reduction of CO2 to acetate due to suboptimal intermediate adsorption energy imposed by the linear scaling relationship of d-band theory. We describe a deposition-etching strategy that tunes the sp2/sp3 hybridization of carbon in diamond to tune the adsorption equilibrium of intermediates for CO2 reduction to acetate, which circumvents the constraints of the d-band electrons. This metal-free catalyst achieves a Faradaic efficiency of 62.7% for CO2-to-acetate conversion and demonstrated 100 hours durability. Mechanistic studies reveal that introducing sp2-carbons into the sp3-carbon matrix can control the adsorption energies of *CO2 and *CO. The sp2/sp3-carbon active sites facilitate the formation of the *CHO intermediate, which is asymmetrically coupled with the *COL to generate acetate. Electrocatalytic CO2-to-acetate remains challenging for metal catalysts due to the linear scaling relationship. Here, the authors report a deposition-etching strategy to modulate sp2/sp3 carbon hybridization in diamond, regulating adsorption equilibrium of key intermediates for acetate formation.