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.