Screening of the Transition Metal Single Atom Anchored on α-Borophene Catalysts as a Feasible Strategy for Electrosynthesis of Urea

Theoretical study of the electrochemical CO2 reduction reaction (CO2RR) and N2 reduction reaction synergistic synthesis of urea via C–N bond coupling, which has provided a high-efficiency approach to developing renewable energy conversion and storage, could also play a significant role in reducing carbon dioxide emissions. However, the practical design and development of electrocatalysts with high activity and selectivity for urea exhibits remain many challenges. Herein, building up a screening strategy based on density functional theory calculations on the transition metal single atom anchored on α-borophene nanosheets provided a route for systematically exploring catalytic activity and electronic properties of the catalyst during CO2 and N2 electroreduction. M@α-B (Ti, Cr, Nb, Mo, and Ta) exhibits promising catalytic activity and selectivity toward the production of urea with the working potentials of −0.31, −0.16, −0.32, and −0.31 V, respectively, during the electrochemical reaction process. Furthermore, the superior activity is closely related to the d-band center and the charge density transfer of active center atoms. To gain insights into the intrinsic correlation between the binding and structural properties, the d-band center position of these M@α-B materials and the limiting potential are used to estimate the catalytic activity of catalysts. Thus, a volcano plot has established a base on the limiting potential with the d-band center positions, and a new descriptor (φ) is suggested to gain insights into the intrinsic correlation from the viewpoint of atomic properties, which involves the electronegativity and the number of d orbital electrons (Nd) of metal atoms. Therefore, a moderate limiting potential (−0.4 < UL < 0 V) and d-band center (−0.2 < ?d < 0.8 eV) lead to high catalytic activity and both thermodynamic and electronic properties of materials. The theoretical landscape for screening M@α-B toward CO2 and N2 conversion into urea will provide a practical approach to gaining insights into the electrochemical reaction mechanism for urea synthesis. It also motivates the experimental efforts to explore the electrocatalysts for other electrochemical reactions.