Two-Dimensional Metal–Organic TM ₃ (HITP) ₂ Monolayers as Promising Bifunctional Single-Atom Electrocatalysts for the Nitrogen Reduction Reaction and Hydrogen Evolution Reaction

This work systematically investigates the electrocatalytic performance of two-dimensional (2D) metal-organic frameworks (MOFs) with the general formula TM₃(HITP)₂, where TM represents 3, 4, and 5d transition metals, as bifunctional single-atom catalysts for both the nitrogen reduction reaction (NRR) and hydrogen evolution reaction (HER). Through high-throughput screening and first-principles calculations, Nb₃(HITP)₂ and Tc₃(HITP)₂ demonstrate superior NRR performance, characterized by low limiting potentials (-0.92 and -0.86 V, respectively) and high selectivity against the HER. Additionally, Os₃(HITP)₂ and Ir₃(HITP)₂ exhibit outstanding HER catalytic activity, evidenced by near-optimal hydrogen adsorption free energies (Δ<i>G</i> _*H = 0) and remarkably low overpotentials (-0.09 and 0.07 V), rivaling the performance of conventional Pt(111) catalysts. All screened catalysts exhibited robust stability in terms of binding energy, cohesive energy, dissolution potential, and thermal stability (verified by <i>ab initio</i> molecular dynamics simulations). This study unveils a class of bifunctional single-atom electrocatalysts for NRR and HER, providing a theoretical foundation for the rational design of multifunctional 2D MOF-based catalysts and promising solutions for sustainable ammonia synthesis and clean energy applications.