Heteroatom‐Engineering Promoted Co ₉ S ₈ Bi‐functional Electrocatalyst for Hydrazine‐Assisted Hydrogen Production at Industrial Current Density

ABSTRACT Hydrazine‐assisted water electrolysis is promising to achieve energy‐saving hydrogen production in combination with removal of hydrazine contamination, but efficient electrocatalysts to accelerate hydrogen evolution and hydrazine oxidation reactions (HER and HzOR) collaboratively remain challenging. Here, we report the synthesis of Fe and P co‐doped Co 9 S 8 (Fe, P‐Co 9 S 8 ) nanocorals as bifunctional electrocatalysts toward HER and HzOR, with the industrial current density of ±500 mA cm −2 at only −280 and 225 mV versus RHE in 1.0 m KOH, respectively. The combined experimental and theoretical analysis unveil the electronic regulation via Fe and P co‐doping, not only lowers the water dissociation barrier and optimizes the H * adsorption/desorption for HER, but also favors the deprotonation kinetics for HzOR. When integrated into an anion‐exchange membrane electrolyzer, Fe, P‐Co 9 S 8 achieves outstanding hydrazine‐assisted electrolysis with a cell voltage of only ∼404 mV at 500 mA cm −2 – far lower than that of conventional water splitting. This energy‐saving hydrogen production can be directly powered by a poly‐Si solar cell or direct hydrazine fuel cell (DHzFC). Simultaneously, hydrazine‐containing wastewater (0.5 M ) is rapidly decomposed to ∼7 ppb, below the allowable threshold for industrial recycled water. These results underscore the strong practical potential of Fe, P‐Co 9 S 8 catalysts in addressing both energy and environmental challenges.