A systematic computational investigation of the water splitting and N2 reduction reaction performances of monolayer MBenes

Abstract

Recently, transition metal borides (MBenes, analogous to MXenes) have attracted interest due to their potential applications in energy conversion and storage. In this work, we performed density functional theory calculations to systematically explore the exfoliation properties of 14 MAlB phases and their water splitting and N₂ reduction reaction (NRR) performances. Results showed a linear relationship between the binding energy and exfoliation energy with the coefficient (R²) of 0.95, indicating that the lower the binding energy of element Al in MAlB (M₂AlB₂), the higher the exfoliation energy required to synthesize monolayer MB from MAlB (M₂AlB₂). NiB (B site) was predicted to possess the best electrocatalytic activity for water splitting, hydrogen evolution reaction (HER), and oxygen evolution reaction (OER) among the studied MBenes, and overpotentials on the NiB surface were calculated to be 0.08 V (for HER) and 0.37 V (for OER), respectively. The electronic properties and dynamic simulations indicated that NiB is the best candidate catalyst for water splitting. Conversely, the Fe site on FeB (FeB-Fe) was predicated to have the highest nitrogen reduction reaction (NRR) activity among the studied MBenes, with the overpotential η_NRR of 0.11 V. Furthermore, the B site of TaB (TaB-B) was identified as the best NRR catalyst against HER among the studied MBenes considering the HER side reaction.