Ultralow‐Loading Ir Single Atoms Ligated by Multiple Bimetal Selenides in Spindle Heterostructures Derived From Porous Ni─Fe Metal‐Organic Frameworks for Efficient and Durable H 2 Production via Water Splitting

ABSTRACT Hydrogen (H 2 ), with the highest gravimetric energy density among chemical fuels, is a promising energy carrier, motivating the development of electrocatalysts for its efficient and durable production. Single‐atom catalysts (SACs) maximize atomic utilization; however, their activity and stability are still limited by atom aggregation during electrolysis. Herein, we report ultralow‐loading Ir SACs (3.82 wt.%) ligated through multiple nickel selenide and iron selenide sites in porous spindle heterostructures (Ir‐NS/FS), derived from porous nickel–iron metal–organic frameworks through chemical vapor deposition of Ir and Se. Strong coordination between isolated Ir single atoms and NS/FS sites suppresses agglomeration while Se atoms serve as hydrogen‐trapping ( * H) sites for high catalytic activity. The high surface roughness and porosity of Ir‐NS/FS also provide a 3.6× higher electrochemically active surface area than RuO 2 , whereas its hydrophilicity improves electrolyte wetting and reaction kinetics. Consequently, the Ir‐NS/FS(+)//Ir‐NS/FS(−) water‐splitting electrolyzer, yielding H 2 production, exhibit superior performance with cell voltages lowered by up to 170 mV at 200 mA cm −2 compared to commercial RuO 2 (+)//Pt‐C(‐) benchmark. Additionally, Ir‐NS/FS(+)//Ir‐NS/FS(−) achieves stable voltages over continuous 5000 cycles. Density functional theory calculations reveal that Ir atoms act as the primary hydrogen‐evolution active sites, while the favorable formation energy of Ir–NS/FS ensures robust stability.