Acetonitrile-driven universal CO production across diverse metal catalysts

Electrocatalytic CO₂ reduction to valuable chemicals with exceptional selectivity is highly desirable. However, it is still challenging to bypass the competitive hydrogen evolution reaction (HER) and branched pathways via regulating the structure of catalysts. Herein, we disclose an unconventional solvent regulation strategy to realize near-unity CO₂-to-CO conversion across diverse metal catalysts including Pt, Fe, Co, Ni, Mo, W, Nb, Cu, Ag, Au, Zn, Sn, and In. The water content in the acetonitrile electrolyte is precisely controlled, and the ratio of hydrogen evolution shows a positive correlation to the hydrogen binding energy of metal elements and the concentration of water. Importantly, we find that the acetonitrile could impair the interaction between *CO and metal electrode and thus promote the desorption of *CO. As a result, the Cu electrodes display poor activity to produce hydrocarbons in acetonitrile, unlike that in aqueous solutions, and near 100% CO Faradaic efficiencies over a wide potential window (−1.9 to −2.4 V vs. Fc/Fc⁺) are achieved at a water concentration of 0.19 M. This work reveals the solvent effect on determining the CO₂RR selectivity, which adds a new dimension to tailoring the final products besides catalyst optimization.