Steric and hydrophilic/hydrophobic effects of organic cations on electrochemical CO reduction

The identity of cations plays a critical role in electrochemical CO₂ and CO reduction reactions. While most research has focused on elucidating the effects of alkali metal cations, the influence of organic cations, which are widely employed in practical anion exchange membrane (AEM) electrolyzers, remains underexplored. Here, we systematically investigate the effects of a series of organic cations with varying sizes and hydrophilic/hydrophobic properties on the CO reduction reaction (CORR). By combining electrochemical online mass spectrometry for kinetic analysis, in-situ Raman spectroscopy for interfacial species characterization, and ab initio molecular dynamics (AIMD) simulations to probe interfacial structures, we uncover that the structure of organic cations significantly influences the accessibility of interfacial water to the electrode surface, and thus the potential-dependent behavior of surface *H coverage, ultimately modulating the CORR selectivity. These findings provide new insights into the mechanisms governing CORR and can guide the development of efficient AEM electrolyzers for CO conversion.