Directing the selectivity of CO₂ electroreduction to target C₂ products via non-metal doping on Cu surfaces

Abstract

Understanding the late stages of the electrochemical CO2 reduction reaction (CRR) in the formation of various C2 products provides great opportunities for fully achieving a selective CRR to target products. Here, we report, for the first time, that C2 product (including ethylene, ethane and ethanol) selectivity can be directed by the active site's oxygen affinity on a range of non-metal doped copper surfaces (Cu–X). Through theoretical evaluation of adsorption energetics of key post-C2-coupling intermediates, we demonstrate how branching reaction pathways are competing with each other and how selectivity for different products is achieved. The oxygen affinities of different active sites on Cu–X catalysts, including the dopant atom and Cu sites, are identified as descriptors for C2 product selectivity. The ethylene pathway is shown to be favored on Cu–X surfaces doped with strong oxygen affinity atoms, such as boron. Ethane selectivity is generally boosted by Cu–X, whereas ethanol generation is suppressed by non-metal doping on Cu surfaces. Bader charge analyses of electron distribution on intermediates and electronegativity analyses of non-metal dopant atoms are integrated to identify the impact of intrinsic electronic properties on adsorption behaviour, together with the resultant C2 product selectivity on Cu–X catalysts. Our findings shed light on controlling product selectivity by modulating oxygen affinity in complex electrochemical reactions.