Heterostructured Palladium–Nickel Sulfide on Plasma-Activated Nickel Foil for Robust Hydrogen Evolution

Transition-metal sulfides are among the effective electrocatalyst candidates for H₂ evolution (HER); however, they still cannot compete with Pt-based electrodes for renewable energy applications. To overcome this issue, grid-matched palladium–nickel sulfides (Pd₄S/Ni₃S₂) are successfully engineered on the holey surface of nickel foil (HNF), which is first treated with a non-thermal plasma (HPNF) generated by a dielectric barrier discharge. The synthesized heterogeneous Pd₄S-Ni₃S₂/HPNF catalyst results in the electron redistribution on the phase interfaces, enhancing the desorption ability of H* species. Consequently, Pd₄S-Ni₃S₂/HPNF presents a high HER activity, and the overpotentials for generating 10 (j₁₀) and 500 (j₅₀₀) mA/cm² are about 44 and 247 mV. Meanwhile, the catalyst retains good electrocatalytic stability over 50 h at j₁₀₀. In addition, the H₂ amount of Pd₄S-Ni₃S₂/HPNF driven by the current j₁₀ can reach 11.25 mmol/h, which is competitive with other presently available high-performance electrocatalysts. The theory and in situ Raman spectroscopy results indicate that Pd₄S and the heterointerfaces between the Pd₄S and Ni₃S₂ phases are the main active catalytic sites for H₂ evolution and that the Pd weakens the S–H_ads bonds, enhancing the reactive kinetics of the Volmer and Heyrovsky steps. This work provides a new and green approach for engineering highly active and stable electrocatalysts for clean hydrogen production.