Abstract
Acidic CO(2) electroreduction offers enhanced carbon utilization efficiency compared to neutral/alkaline systems but faces dual challenges of hydrogen evolution dominance and salt precipitation-induced instability when using conventional metal cation electrolytes. Here, we report a tetramethylammonium (TMA(+)) cation-mediated strategy that simultaneously achieves exceptional selectivity and stability toward CO production over Au nanoparticles, a near-unity Faradaic efficiency at an industrial-level current density, while maintaining continuous operation for 2600 hours without salt precipitation. Through in situ electrochemical atomic force microscopy, we directly visualize the potential-dependent dynamic assembly of TMA(+) into multilayered structures within the electric double layer, a phenomenon previously predicted theoretically. The assembled TMA(+) layers disrupt the hydrogen-bond network for proton transport, and meanwhile, their hydrophobicity and the high TMA(+)-bicarbonate solubility prevent salt precipitation, which leads to both substantial selectivity and stability. This work not only introduces an advanced paradigm for propelling the CO(2) electrolysis toward practical applications but also broadens our understanding of the cation effect.