Transition metal atom on the two-dimensional Dirac structure RhB4/OsB4: A novel multifunctional electrocatalyst

Abstract

The design of low-cost multifunctional electrocatalysts with high carrier mobility, high surface free energy and base surface activity facilitates hydrogen evolution reactions (HER) and oxygen reduction reactions (ORR), which are essential for the development of clean energy. Recent studies have shown significant progress in developing HER/ORR bifunctional catalysts, such as transition metal alloys, oxides, sulfides, and carbon-based composites. These materials are highly efficient in catalysis and help reduce costs. In this work, density functional theory is used to predict the performance of single atom catalysis (SACs) embedded with transition metal (TM) using two-dimensional (2D) Dirac node-ring semi-metal RhB4/OsB4 monolayer as substrate. Systematic calculations show that the TM@RhB4/OsB4 structure with thermodynamic and kinetic stability presents multiple active sites on the basal surface. Notably, Fe@RhB4 is an excellent hydrogen evolution reaction HER catalyst because Dirac cones occur near the Fermi level of this structure, providing high carrier densities and accelerating charge transfer between the catalyst and reaction intermediates. When the substrate RhB4/OsB4 is modified by Sc and Cu atoms, the band gap of the structure becomes small, which increases the conductivity of the original structure. The ΔGH* values of Sc@RhB4 and Cu@OsB4 were 0.118, and 9.38 meV, respectively, outperforming the ideal catalyst Pt. In addition, it is found that Fe@RhB4, and Mn@OsB4 exhibit outstanding catalytic properties for the oxygen reduction reaction (ORR), with overpotentials of 0.41V, and 0.40V, respectively, surpassing the performance of the reference catalyst Pt. It is exciting that the Fe@RhB4 exhibits ideal HER/ORR bifunctional electrocatalytic properties. This study will provide a theoretical basis for the development of multifunctional electrocatalysts in the field of Dirac nodal ring semi-metal materials by single atom doping technology.