Engineering multiphasic MoSe₂/NiSe heterostructure interfaces for superior hydrogen production electrocatalysis

Constructing heterojunction nanocomposites with optimized active sites and interface electronic structures is promising for hydrogen evolution reaction (HER). Herein, we present an interface engineering strategy to fabricate two heterostructures, triphase MoSe₂/NiSe-1 including 1T-MoSe₂, 2H-MoSe₂ and hexagonal phase NiSe (H-NiSe), and tetraphase MoSe₂/NiSe-2 including 1T-MoSe₂, 2H-MoSe₂, H-NiSe and rhombohedral phase NiSe (R-NiSe). MoSe₂/NiSe-1 exhibited remarkably enhanced HER activity with an overpotential of 30 mV at 10 mA cm⁻², and negligible voltage change even when operated for 40 h. The strong electronic synergistic interaction between the different interfaces of mixed MoSe₂/NiSe greatly enhanced the HER performance. Density functional theory calculations helped rationalize why the combination of three phases is more active, by increasing the interface electron concentration, facilitating electron transfer and decreasing the free energy ΔG_H2O and ΔG_H*. This work provides a rational strategy to design and assemble stable and high-performance multiphasic heterojunctioned HER electrocatalysts.