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.