Tailoring Cu Electrodes for Enhanced CO₂ Electroreduction through Plasma Electrolysis in Non‐Conventional Phosphorus‐Oxoanion‐Based Electrolytes

Abstract

This study presents a green and facile technique for producing micro/nano‐structured and porous Cu electrodes via in‐liquid plasma electrolysis using phosphorous‐oxoanion‐based electrolytes. The Cu electrodes exhibit unique surface structures, including octahedral nanocrystals besides nanoporous and microporous structures, depending on the employed electrolyte. The incorporation of P‐atoms into the Cu surfaces is observed. The resulting Cu electrodes have increased roughness, leading to higher current densities for CO2 electroreduction reaction. The selectivity of the modified Cu electrodes towards C2 products is highest for the Cu electrodes treated in Na2HPO3 and Na3PO4 electrolytes, while those treated in Na2H2PO2 produce the most H2. The Cu electrode treated in Na3PO4 produces ethylene (23%) at –1.1 V vs. RHE, and a comparable amount of acetaldehyde (15%) that is typically observed for Cu(110) single crystals. The enhanced selectivity is attributed to several factors, including the surface morphology, the incorporation of phosphorus into the Cu structure, and the formation of Cu(110) facets. Our results not only advance our understanding of the influence of the electrolyte’s nature on the plasma electrolysis of Cu electrodes, but also demonstrates that in‐liquid plasma treatment and phosphorous‐doping of Cu surfaces hold promise for the development of efficient Cu electrocatalysts for sustainable CO2 conversion.