Efficient CO-to-Acetate Conversion Electrocatalyst Screened by Pressurization-Compatible Operando Raman Spectroscopy.

The conversion of CO to acetate represents a selective and efficient pathway among CO2/CO-to-C2+ electroreduction routes, with recent advancements being partly attributed to pressurized electrolyzer designs. Pressurization establishes bulk CO enrichment that enhances mass transport, yet methodologies for designing catalyst surfaces to efficiently accommodate and electroreduce dense *CO intermediates remain underdeveloped. We systematically investigate *CO adsorption coverage and affinity across copper surfaces with varying structural features, correlating these properties with CO-to-acetate performance. Notably, operando Raman spectroscopy conducted in a custom flow reactor replicating pressurized environments reveals pressure-dependent *CO adsorption and conversion dynamics on distinct Cu surfaces. We discover that Cu twin boundaries optimally support both pressurization-enhanced CO adsorption and subsequent conversion steps, achieving Faradaic efficiencies of 91% for total C2+ products and 82% for acetate at 10 atm CO pressure, surpassing all reported monometallic Cu catalysts. We contributed a practical tool for the operando characterization of pressurized gas-fed electrocatalytic processes.