Strain engineering of the electrocatalytic activity of nitrogen-rich BeN4 Dirac monolayer for hydrogen evolution reaction

The strong bond energy and short bond length of N≡N triple bond make it a challenging target for synthesizing nitrogen-rich compounds. However, recent research has successfully fabricated atomic-thick BeN4 layers under high pressure (Bykov et al., 2021). Beryllonitrene, a new 2D material, consists of a Be atom and polymeric nitrogen chains and has anisotropic Dirac cones located near the Fermi level. This distinguishes it from graphene, which has isotropic Dirac cones, bulk PtTe2 and 2D borophene, which have Dirac cones located far from the Fermi energy. The anisotropic Dirac cones in beryllonitrene result in ultrahigh carrier mobility and the potential for direction-dependent quantum devices. In this study, we systematically investigated the hydrogen evolution reaction (HER) catalytic activity of nitrogen-rich, non-precious BeN4 monolayer using first-principles DFT calculations. Our results demonstrate that BeN4 monolayer is thermally stable, and Be vacancy is the most energetically favorable site for hydrogen adsorption. We also found the Gibbs free energy (ΔGH∗) of H∗ coverage can be tuned to an optimal value of |ΔGH∗|≤ 0.2 eV through strain engineering, significantly enhancing the HER electrocatalytic activity of BeN4 monolayer. Furthermore, we examined both the homolytic Tafel reaction and heterolytic Heyrovsky reaction for HER mechanism using reaction kinetics and AIMD simulations. These findings can contribute to the development of high-performance, non-precious, and nitrogen-rich 2D catalysts for HER in future research.