A "Two-Pronged" Strategy to Boost Hydrogen Evolution Kinetics on NiFe-Based (Oxy)hydroxides via Oxygen Deficient...

NiFe (oxy)hydroxides have been regarded as one of the state-of-the-art catalysts for oxygen evolution reaction (OER). Unfortunately, the sluggish hydrogen evolution reaction (HER) kinetics limit its application as bifunctional electrocatalyst for alkaline overall water splitting (OWS). Herein, a "two-pronged" strategy is proposed to construct highly active oxygen deficient Ni-Mo-Fe coordinate structures in NiFe (oxy)hydroxide (NFM-OV_R/NF), which simultaneously reduces the energy barrier of Volmer and Heyrovsky steps during alkaline HER process and significantly accelerate the reaction kinetics. Consequently, NFM-OV_R/NF delivers overpotentials as low as 25 and 234 mV to achieve 10 and 1000 mA cm^-2 in 1.0 M KOH, respectively. Furthermore, benefiting from excellent HER and OER activity, NFM-OV_R/NF exhibits a remarkable OWS activity with cell voltages of 1.44 V and 1.77 V at 10 and 1000 mA cm^-2 in 1.0 M KOH, and displays ultralong-term stability for 600 h at 500 mA cm^-2, while remaining durable for 300 h in an alkaline water electrolyzer in 30% KOH at 80 °C. The calculated price per gallon of gasoline equivalent for the produced H₂ is $ 0.92, which is much lower than 2026 U.S. Department of Energy target ($ 2.00), demonstrating feasibility and practicability of NFM-OV_R/NF for industrial applications.