Double transition metal atoms supported on defective borophene as efficient electrocatalysts for nitrogen reduction: a theoretical study

Electrocatalytic nitrogen reduction reaction (NRR) provides a promising approach for ammonia production under mild conditions. Developing high efficiency catalysts is the key and challenge for their practical appli-cation. Here, we employ density functional theory (DFT) to design a series of transition metal double-atom catalysts (DACs) with defective beta 12-borophene (DB-Hij) as the substrate, namely TM2@DB-Hij, where TM = Sc-Zn, Zr-Rh (expect Tc) and Hf-Os. Two potential candidate catalysts Zr2@DB-H12 and Hf2@DB-H12 were selected based on three screening strategy. DFT calculation shows that on the two DACs, NRR starts from an end -on adsorption configuration of N2 and proceeds via the enzymatic mechanism. These two DACs not only exhibit excellent catalytic activity, with the limiting potentials of-0.28 and-0.39 V, respectively, but also effectively suppress the competing hydrogen evolution reaction (HER). Moreover, the effects of two substrates on the catalytic performance of TM2@DB-H12 were also investigated. The existence of Ag(111) substrate prepared in the experiment reduced the activity of the designed DACs, while the NRR activity was improved when graphene was used to replace Ag(111). The present study indicates that the substrates affect the electrocatalytic performance of catalysts to a certain extent, which should be considered in future research.