Highly selective and scalable CO₂ to CO - Electrolysis using coral-nanostructured Ag catalysts in zero-gap configuration

The direct electroreduction of CO₂ to pure CO streams has attracted much attention for both academic research and industrial polymer synthesis development. Here, we explore catalytically very active, coral-structured Ag catalyst for the generation of pure CO from CO₂-feeds in lab-bench scale zero-gap CO₂ electrolyzer. Coral-shaped Ag electrodes achieved CO partial current densities of up to 312 mA cm⁻², EE_CO of 38%, and FE_CO clearly above 90%. In-situ/operando X-ray Absorption Spectroscopy revealed the sustained presence of Ag⁺ subsurface species, whose local electronic field effects constitute likely molecular origins of the favorable experimental kinetics and selectivity. In addition, we show how electrode flooding in zero-gap CO₂ electrolyzer compromises efficient CO₂ mass transfer. Our studies highlight the need for a concomitant consideration of factors related to intrinsic catalytic activity of the active phase, its porous structure and its hydrophilicity/phobicity to achieve a sustained high product yield in AEM zero-gap electrolyzer.