NiS-cored electrocatalysts with universal metal armor for enhanced activity and stability in alkaline water electrolysis

Transition metal sulfides exhibit promising catalytic activity for the hydrogen evolution reaction (HER). practical deployment is severely hampered by rapid performance degradation stemming from inherent structural metastability. To overcome this, we introduce a universal active-metal armoring strategy that simultaneously boosts activity and durability by constructing a protective yet electrochemically functional metal overlayer on a NiS core. As a proof of concept, an Ag armor was deposited onto NiS nanosheets via a facile electrodeposition process. The Ag shell acts as a dual-functional armor, which electronically optimizes the hydrogen adsorption free energy to near-thermoneutral values, and physically suppresses Ni 2+ dissolution by approximately tenfold during a 50 h test at 200 mA cm −2 , the destructive reconstruction of the NiS core is effectively suppressed. Consequently, NiS@Ag catalyst delivers a low overpotential of 77 mV at 10 mA cm −2 and maintains remarkable stability for 120 h at 200 mA cm −2 in 1 M KOH. The versatility of this concept is validated by substituting Ag with cost-effective Ni and Co overlayers, which yield comparable performance enhancements. This work establishes a general and scalable principle for crafting robust, high-performance, and affordable electrocatalysts for sustainable hydrogen generation.