K₂PtCl₄-induced structural reconstruction of high-entropy sulfide hollow nanospheres for enhanced hydrogen evolution

We report the synthesis of K₂PtCl₄-treated high-entropy sulfide (HES) nanospheres via a two-step liquid-phase synthesis involving solvothermal formation of (Co,Ni,Cu,Zn,Mn)₃S₄ hollow spheres and subsequent K₂PtCl₄ solution treatment. The resulting nanospheres exhibit a well-defined hollow morphology. The K₂PtCl₄ solution treatment induces partial structural reconstruction of the HES framework, producing a Pt-containing amorphous region while retaining part of the crystalline spinel domain. The resulting catalyst also demonstrates excellent catalytic activity for the hydrogen evolution reaction (HER), delivering low overpotentials of 50 mV at 10 mA cm^-2 in 1.0 M KOH and 49 mV at 10 mA cm^-2 in 0.5 M H₂SO₄. It also demonstrates good long-term durability, retaining 71% and 98% of its initial current density after 60 h of continuous operation at constant potentials corresponding to an initial current density of 100 mA cm^-2 under alkaline and acidic conditions, respectively, and maintaining almost constant polarization behavior after 5000 CV cycles under both conditions. These findings highlight the potential of K₂PtCl₄-treated HES as efficient and durable electrocatalysts for sustainable hydrogen production across a wide pH range.