Hydrogen Spillover Mechanism of Superaerophobic NiSe₂‐Ni₅P₄ Electrocatalyst to Promote Hydrogen Evolution in Saline Water

Abstract The hydrogen spillover mechanism of metal‐supported electrocatalyst can significantly improve HER activity. However, the rational design of binary heterojunction hydrogen spillover electrocatalysts remains a challenge. Here, a NiSe₂‐Ni₅P₄ heterojunction electrocatalyst with superaerophobic structure is synthesized by using a simple substrate self‐derived strategy. Experimental characterization and theoretical calculation reveal the hydrogen spillover mechanism of NiSe₂‐Ni₅P₄ heterogeneous electrocatalyst. NiSe₂ and Ni₅P₄ synergistically promote the adsorption/dissociation of H₂O and the adsorption of H^*, respectively. The smaller ΔΦ effectively reduced the electron density at the interface, weakening the proton adsorption at the interface and promoting the migration of H^* from NiSe₂ to Ni₅P₄. The NiSe₂‐Ni₅P₄ exhibits excellent HER activity in alkaline electrolyte, requiring only a potential of 65, 270 mV to achieve a current density of 10, 500 mA cm⁻², respectively, and a stability of up to 200 h. Moreover, the design of NiSe₂‐Ni₅P₄ with superaerophobic structure can reduce the deposition of impurity ions on the electrode surface and avoid Cl⁻ corrosion of the electrode, which results in NiSe₂‐Ni₅P₄ showing better HER activity and stability than commercial Pt/C in brackish water. This study deepens the understanding of hydrogen spillover mechanism of binary heterojunction electrocatalysts, broadens the application of hydrogen production in complex water quality.