Single- and dual-atom first-row transition-metal decorated B₁₂N₁₂ nanocages for hydrogen evolution: A density functional theory study

Single-atom (TM@B₁₂N₁₂) and dual-atom (2-TM@B₁₂N₁₂) decorated boron nitride nanocages, where TM represents first-row transition metals, are investigated as hydrogen evolution reaction (HER) catalysts using density functional theory (DFT). Full geometry optimization and electronic-structure calculations are combined with hydrogen adsorption free energies and detailed reaction profile analysis. Notably, metal decoration activates the B₁₂N₁₂ cage by reducing the frontier orbital gap and refining the work-function values, thereby improving charge-transfer characteristics and proton binding. Among single-atom systems, titanium- and vanadium-decorated nanocages exhibit near-thermoneutral hydrogen adsorption (ΔG_H* = −0.02 to −0.03 eV). For dual-atom doping, the 2-Cr@B₁₂N₁₂ system shows a similarly balanced adsorption (−0.05 eV). Furthermore, these catalytic systems have low hydrogen adsorption-desorption free-energy barriers along the HER pathways, with ΔG_RLS = 0.15 eV for the vanadium- and 0.16 eV for the dichromium-decorated nanocages. Noncovalent interaction and structural analysis indicate that the enhanced activity originates from the charge delocalization and effective 3d-1s interaction.