Identifying the Active Sites in MoSi 2 @MoO 3 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 MoSi 2 and MoO 3 together through Oxygen doping to construct heterojunctions. Benefiting from the synergistic effects between the MoSi 2 and MoO 3 , the obtained MoSi 2 @MoO 3 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.