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

Abstract

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.

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