Cooperativity in Bimetallic SACs: An Efficient Strategy for Designing Bifunctional Catalysts for Overall Water Splitting

Designing novel support materials for single-atom catalysts (SACs) is a recent challenge for the water splitting reaction. Despite advances in 2D nanomaterials and their heterostructures for application in catalysis, investigation on finite-size supports is scarce. Recently, flat boron has emerged as a fascinating concept in cluster science. Accordingly, in the present study, the ability of the finite-size quasiplanar cluster of boron, namely B₃₆, as a potential support for transition metals from 3d series (Sc–Zn) is theoretically investigated. We found that B₃₆ is firm to support the single metal atom steadily. Then, the electrocatalytic activity of doped B₃₆ was systematically investigated toward the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). Activity analysis indicates that Ni-doped B₃₆ and Ti-doped B₃₆ are promising electrocatalysts for OER and HER, respectively, outperforming pristine B₃₆. However, despite the superior performance of single-atom doping over the pristine B₃₆, none of the examined systems can act as a bifunctional catalyst for both OER and HER. In the second part, we focus on the B₃₈ cluster, because the double-hole structure provides additional opportunities to tune its electronic structure via dual doping and achieve improved catalytic performance. Four pairs of 3d transition metals, FeCr, FeCo, FeNi, and FeCu, are considered to investigate the intermetallic cooperativity effect on the OER and HER activities. Based on the results, a greater degree of synergistic effect is observed in FeNi-codoped B₃₈. The computed Gibbs free energy for OER and HER confirms the feasibility of OER on an Fe center and HER on a Ni center. Therefore, it is expected that the strategy of bimetal codoping on a single-material platform can provide a new route for designing a bifunctional electrocatalyst for overall water splitting.