Screening Strategies for Diatom Metal-Doped β-Borophene Nanosheet Catalysts for Electrochemical Synthesis of Ammonia Using Density Functional Theory

Abstract

Electrocatalysis is a promising approach for ammonia production under ambient conditions. However, practically, owing to the competing hydrogen evolution reaction (HER), the Faradaic efficiency is low, and it is difficult to activate the inert N≡N. The theoretical screening method based on density functional theory calculations is a novel technique for developing and designing nitrogen reduction reaction (NRR) diatom catalysts (DACs). We proposed an NRR new type of DAC doped on β-borophene (B-β) nanosheets exhibiting enhanced catalytic activities for the NRR through the pull–pull effect of dual-metal sites and donor–acceptor coupling. By systematically evaluating the stabilities, selectivities, and activities of 24 diatom-doped β-borophene (M2@B-β) candidates, Mo2@B-β was found to be a promising NRR electrocatalyst with a low limiting potential of −0.23 V for the NRR and a high overpotential of −0.16 V for the HER. The limiting potentials for Cr2@B-β, Mn2@B-β, and Re2@B-β were −0.52, −0.51, and −0.35 V, respectively, making them suitable electrocatalysts for the NRR. Based on the Sabatier principle, we proposed two descriptors, ΔG(*N) and d-band center, as the criteria for screening and designing catalysts with high catalytic activities to reveal the intrinsic correlation between adsorption properties and structural properties. Based on the ΔG(*N) function, a volcano plot was built to predict trends in the activities. The difference, ΔG(*N2) – ΔG(*H), was used as the selectivity descriptor, where the negative values of ΔG mean that the adsorption of N2 dominates over the adsorption of H on the surface of M2@B-β. This study thus provides a feasible strategy for designing NRR electrocatalysts and is helpful for the fast screening of efficient DACs for other electroreduction reactions.