FeSe₂-BiSe₂-CoSe₂ Ternary Heterojunction for Efficient Hydrogen Evolution Reaction Under pH-Universal

The construction of heterostructures has been recognized as an effective strategy for enhancing material activity and stability. Herein, a ternary heterojunction FeSe₂-BiSe₂-CoSe₂ was synthesized via a hydrothermal selenidation reaction. The significant electronegativity difference between Bi and Fe/Co triggers charge transfer within the FeSe₂-BiSe₂-CoSe₂ lattice. Furthermore, the abundant pore structure of FeSe₂-BiSe₂-CoSe₂ provides efficient pathways for electron diffusion, significantly enhancing the HER catalytic kinetics. Results demonstrate that FeSe₂-BiSe₂-CoSe₂ exhibits outstanding HER activity in both acidic and alkaline media. In 0.5 M H₂SO₄, it exhibits an overpotential of only 44 mV with a Tafel slope of 108 mV dec^-1. In 1 M KOH, the corresponding overpotential is 188 mV, with a Tafel slope of 45 mV dec^-1 at 10 mA cm^-2. This study constructs electron-rich active sites through electronic structure regulation, providing valuable insights for designing low-cost, high-performance transition metal selenide HER catalysts.