Unraveling the effect of transition-metal doping on the structural, electronic, and electrocatalytic HER performance of monolayer HfTe2

Abstract

Monolayer HfTe₂ is a promising electrocatalyst for the hydrogen evolution reaction (HER), yet its doping-tuned activity remains underexplored. Using DFT, we systematically investigated the effect of 23 transition-metal (TM) dopants, and identified Fe, Co, Ru, Re, Ir, and Au as top performers, since their hydrogen adsorption free energy ΔG_H approaches that of Pt (–0.09 eV). Electronic structure analysis reveals that doping shifts the TM-nd and adjacent Te-5p states toward the Fermi level and establishes the d-band center (ε_d) of the dopant as a key descriptor, with an optimal range of −1.9 to −2.1 eV directly correlating with near-ideal ΔG_H. Formation energies under Te-rich conditions are all negative, confirming doping feasibility. Dissolution analysis identifies Ru balances activity and stability under acidic conditions, while Fe, Co, and Re are susceptible, and Ir, Au resist dissolution. This provides guidelines for HER catalyst design.