Theoretical Screening of Transition Metal-Embedded Ti₂N for High-Efficiency Hydrogen Evolution Reaction

Transition metals (TMs) have been widely employed to realize various electrocatalytic applications of pristine materials. Herein, via density functional theory (DFT), the potential for the hydrogen evolution reaction (HER) of all single TMs embedded in Ti₂N was screened. Our results show that embedded single TMs can tune the hydrogen adsorption with a volcano-like tendency, and Mo-Ti₂N stands out with an optimal Gibbs free energy (ΔG_H) of −0.097 eV. This can be further improved with an optimal ΔG_H close to thermal neutrality by applying 1.2% tensile strain to Mo–Ti₂N, and the excellent exchange current density exceeds that of most conventional metal catalysts. The chemical nature of the Mo–H bond under strain was analyzed by revealing the changes in internal electronic structure and establishing the relationship with adsorption energy. The results reveal the bonding mechanisms to clearly show that a single TM atom embedded in Ti₂N such as Mo-Ti₂N is a feasible electrocatalyst for HER.