Identifying the Active Sites in MoSi₂@MoO₃ Heterojunctions for Enhanced Hydrogen Evolution

Developing Two-dimensional (2D) Mo-based heterogeneous nanomaterials is of great significance for energy conversion, especially in alkaline hydrogen evolution reaction (HER), however, it remains a challenge to identify the active sites at the interface due to the structure complexity. Herein, the real active sites are systematically explored during the HER process in varied Mo-based 2D materials by theoretical computational and magnetron sputtering approaches first to filtrate the candidates, then successfully combined the MoSi₂ and MoO₃ together through Oxygen doping to construct heterojunctions. Benefiting from the synergistic effects between the MoSi₂ and MoO₃, the obtained MoSi₂@MoO₃ exhibits an unprecedented overpotential of 72 mV at a current density of 10 mA cm^-2. Density functional theory calculations uncover the different Gibbs free energy of hydrogen adsorption (ΔG_H*) values achieved at the interfaces with different sites as adsorption sites. The results can facilitate the optimization of heterojunction electrocatalyst design principles for the Mo-based 2D materials.