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

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.