Boosting HER/OER Activity of Ni-FeOOH Through S and V Co-Doping

Rational manipulation of electronic structure and surface reaction energetics is essential for the development of high-performance bifunctional electrocatalysts for overall water splitting. Herein, a transition-metal doping method is proposed to systematically evaluate the activity of Ni-FeOOH modified with V, Nb, Zr, Mn, and Zn. A new S,V, co-doped Ni-FeOOH heterostructure supported on Ni foam is constructed, which induces redistributed electron density, regulated lattice strain, and enriched oxygen vacancies. As a result, the S,V, co-doped Ni-FeOOH catalyst exhibits outstanding oxygen evolution reaction (OER) performance with a low overpotential of 264 mV at 50 mA cm^-2, a small Tafel slope of 28.36 mV dec^-1, ECSA of 25.67 mF cm^-2, and the lowest charge-transfer resistance (R_ct = 1.20 Ω). Meanwhile, the hydrogen evolution reaction (HER) activity is simultaneously enhanced, achieving an overpotential of 99 mV at 10 mA cm^-2 with a Tafel slope of 141.2 mV dec^-1, ECSA of 64.2 mF cm^-2, and R_ct = 1.25 Ω. Notably, the catalyst maintains stable OER/HER performance for 600 h at high current densities of 100, 200, and 400 mA cm^-2, demonstrating exceptional durability under industrially relevant conditions. This work establishes a periodicity-guided dopant-synergy engineering strategy for simultaneously enhancing activity and durability in bifunctional electrocatalysts for alkaline water electrolysis.