Defect engineering in the MA2Z4 monolayer family for enhancing the hydrogen evolution reaction: first-principles calculations

Abstract

Water electrolysis is a sustainable and clean method to produce hydrogen fuel via the hydrogen evolution reaction (HER). Using effective and low-cost electrocatalysts for the HER to substitute expensive noble metals is highly desired. In this study, by using first-principles calculations, we designed a defective MA₂Z₄ monolayer family as two-dimensional (2D) electrocatalysts for the HER, and their stability, electronic properties, and catalytic performance were investigated. As the most representative material of the MA₂Z₄ monolayer family, MoSi₂N₄ was first successfully synthesized in the experiment [Y. L. Hong et al., Science, 2020, 369, 670–674]. Our results reveal that vacancy regulation at the outer Z atom (V_Z) can obviously enhance the catalytic activity toward the HER, compared with the pristine MA₂Z₄. It is also shown that ΔG_H* can be close to 0 eV with V_P vacancies at active site 1, which should be the optimal performance for a HER catalyst. Moreover, we demonstrated that the HER performance prefers the Volmer–Heyrovsky mechanism. Our study provides a strategy for designing MA₂Z₄ monolayer family electrocatalysts, which are predicted to be employed in HER catalysts with low cost and high performance.