Mechanism for CO2 electroreduction into C2 products at the low overpotential: Theoretical insights from an improved electrode/solution interface model

ABSTRACT A CO coverage-dependent Cu(100)/H2O interface model is used to study electroreduction pathways of CO2 towards C2H4 and CH3CH2OH products at the low overpotential with the aim of solving the long disputing on production mechanisms of C2 products. Our results show that previously predicted dimer OCCO may be not a viable intermediate and C-C coupling pathway may occur through reactions of COH with CO into COCOH and COH dimerization into COHCOH species on Cu(100). Thereby, the optimal CO2 electroduction pathways towards C2H4 and CH3CH2OH products can be presented. It is found that present defined CCHOH and CHCOH pathways both are favorable and may be able to occur parallelly during CO2 electroreduction into C2 products, naturally explaining why C2 products can be observed experimentally at low overpotentials on Cu(100). Thereinto, common CH2CH2OH and CHCH2 species can be formed in the parallel pathways wherein CHCH2 intermediate can directly lead to C2H4 product through proton-electron transfer process and CH2CH2OH species is the direct precursor into CH3CH2OH product. Mechanistic understanding towards the productions of C2 products on Cu(100) will open up routes to productions of high-energy fuels and provide significant insights into the design of highly active CO2 electroreduction catalysts operated at low overpotentials.