Switchable CO₂ Electroreduction Induced By the Bismuth Moiety with Tunable Local Structures on Graphene

Abstract

Controlling the chemical environment of the atomically dispersed central atoms doped in the graphene lattice is critical to achieve desirable catalytic performances in carbon dioxide reduction reaction (CO2RR), however, how the local structures of non-transition metal-based single atom (SAs) affect the catalytic performances of CO2RR remains less understood. This study reports the immobilization of bismuth single atom catalysts (SACs) on pristine and nitrogenated graphene nanosheets with switchable catalytic selectivity in the carbon dioxide reduction reaction (CO2RR). Based on systematic physical characterizations and electrochemical analysis, it has been demonstrated that the Bi atom coordinated with four adjacent nitrogen atoms (Bi-N-C) selectively produces carbon monoxide (CO) with high selectivity at low overpotential, whereas Bi SACs bounded with carbon atoms (Bi-C) almost exclusively generate formate (FA). Theoretical investigations reveal that the Bi-N-C catalyst displays the lowest activation barrier for the first hydrogenation step of CO2 to produce *COOH, while Bi-C shows the most preferable pathway towards the formation of *OCHO, which is considered as the important intermediate species to generate FA. The controllable product distributions are dictated by the different local structures of Bi centers in Bi-N-C and Bi-C, and such differences could induce distinct electronic properties of Bi centers and subsequently switch the CO2RR products from CO to FA. This work has substantiated the importance of the fine-regulation of the coordination environment of one of the representative p-blocking SAs to steer the selectivity of CO2RR.