Pressure-Induced Forward-Shift of Proton-Coupled Electron Transfer Step Boosts CO-to-Acetate Throughput.

Regulating the rate-determining step (RDS) constitutes the central challenge in catalysis science, as it governs both reaction efficiency and pathway selectivity. In CO/CO₂ electroreduction, the voltage-insensitive *CO-*CO dimerization - a non-proton-coupled electron transfer (PCET) step - critically limits multi-carbon production rates by restricting accessible current densities below industrial demands. Traditional catalyst modification strategies often induce undesired perturbations to downstream pathways while addressing this bottleneck. Here, we demonstrate a physical microenvironment engineering strategy that reconfigures reaction sequences through pressure modulation. Elevated CO pressure enriches surface *CO coverage, redirecting proton reaction pathways to preferentially hydrogenate *CO intermediates rather than coupling for hydrogen evolution, evidenced by a reduced Tafel slope for acetate and hydrogenated intermediates resolved from high-pressure operando Raman spectroscopy. When integrated with a synthetic Cu-Pd single-atom alloy (SAA) catalyst, the CO-to-acetate conversion system is selective with a Faradaic efficiency of 85%, energy-efficient with an energy efficiency of 33%, and selective with an operation duration of 700 h. Interestingly, our system can maintain a high acetate selectivity (>75%) across an exceptionally broad current density range from 3 to 1500 mA cm⁻ ², potentially compatible with intermittent renewable power sources.