Enhanced electrocatalytic activity of NiCoP/Ni ₅ P ₄ @NiFe-LDH catalysts via Ir doping and oxygen vacancy engineering

Alkaline water electrolysis offers a promising route for large-scale hydrogen production, but its efficiency is limited by the sluggish kinetics of both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER). Herein, we designed a hierarchical composite electrocatalyst comprising iridium-doped nickel-cobalt phosphide nanoparticles (Ir-NiCoP/Ni5P4) encapsulated within nickel-iron layered double hydroxide nanosheets (NiFe-LDH). Oxygen vacancies (OV) were engineered on the surface via sodium borohydride reduction, yielding an optimized catalyst denoted as Ir-NiCoP/Ni5P4@NiFe-LDH-1-OV. The optimized catalyst delivers low overpotentials of 52.7 mV for HER and 197.3 mV for OER at 10 mA cm-2 and maintains remarkable stability over 100 h for overall water splitting. Moreover, the Ir-NiCoP/Ni5P4@NiFe-LDH catalyst exhibits overpotentials of 76.7 and 101.3 mV for HER and the ammonia oxidation reaction A in 1 M KOH + NH3·H2O, respectively.