Novel multi-functional sites in boron-based bi-atom catalysts synergistically boost C-C coupling for efficient CO electroreduction towards ethanol

Abstract

The electrochemical CO reduction reaction (CORR) is faced by challenges in achieving high-value-added C₂ products due to inefficient C–C bond formation and low selectivity. Using first-principles calculations, we propose a framework for boron-based bi-atom doping into a silicene monolayer (B-X@Si) to improve CORR catalytic efficiency. Transition metal (TM)-free B-B@Si and TM-containing B-Cu@Si serve as efficient bi-atom catalysts (BACs) with low limiting potentials (-0.28 and -0.63 V) and low activation barriers for C-C coupling (0.54 and 0.53 eV). The CO* binding strength of active sites with co-adsorbed CO* species follows the order TM < B < B-TM. Remarkably, the interplay within the B-TM pair strengthens CO* adsorption, driven by increased TM involvement, as characterized by the upward shift of the d-band center of TM in B-TM@Si relative to the Fermi level. The coupling kinetics depend on the reactivity of C(CHO*) and CO* fragments within the decoupled CHO-CO* intermediate. Intriguingly, hetero-B-TM@Si systems display a trade-off between stronger CHO* and weaker CO* binding compared to homo-B-B@Si. Among the TMs, Cu is the most appropriate partner for B; the moderate synergistic effect of the B-Cu pair resulting in the smallest augmented C-affinity (CHO*) is offset by the weakest CO* binding strength on Cu itself, ensuring rapid C–C coupling similar to that of B-B@Si. Our BACs offer unique multi-functional active sites due to participation of host atoms (Si*) adjacent to the bi-dopants; these Si-atoms stabilize adsorbates, facilitate the subsequent C–C coupling step, and protect the C–O bond for selective ethanol production. This study provides theoretical insights for the development of advanced BACs with novel multi-adsorbing sites and tailored charge redistribution that enhance CO-to-C₂ conversion.