Neighbouring Cu–B6 electron reservoirs in α-borophene promote long-range C–C coupling to generate C2 products from CO2

Abstract

C–C coupling is the critical step in the electrocatalytic CO₂ reduction reaction (eCO₂RR) for the synthesis of high-value multi-carbon products. Constructing neighbouring active sites of metal single atoms is a reasonable strategy to facilitate the C–C coupling process. However, an appropriate catalyst support to which single atoms are anchored is crucially required to form uniform neighbouring sites. We herein designed a novel α-borophene catalyst with high-density Cu single atoms and studied its electronic structure and C–C coupling mechanism using density functional theory (DFT) calculations. It was found that the Cu atoms were firmly anchored on borophene vacancies, forming the special structure called ‘Cu–B₆ electron reservoirs’, which therefore endowed the catalyst with high-density neighbouring Cu single atoms. The neighbouring Cu–B₆ electron reservoirs could promote the conversion of CO₂ to an adsorbed intermediate *OCHO and achieve a unique long-range C–C coupling. Ab initio molecular dynamics (AIMD) further showed that the Cu–B₆ electron reservoirs enhanced the closeness of approach of C atoms in neighbouring *OCHOH₂ intermediates across a distance of 5.06 Å in the C–C coupling step (2*OCHOH₂ → *OCHCHO + 2H₂O), strongly favouring this long-range coupling process. Overall, this study provides valuable mechanistic insights into the C–C coupling process in terms of the eCO₂RR by constructing high-density neighbouring single atoms on two-dimensional model materials.