Thiomolybdate‐Modified Spinel NiFe ₂ O ₄ Cubes: Unleashing Electrocatalytic Potential for Industrial Overall Water Splitting

ABSTRACT Spinel‐type NiFe ₂ O ₄ exhibits promising application prospects as electrocatalysts for water electrolysis, but its intrinsic properties limit achieving industrial current densities at low voltages. Herein, a dual‐pronged approach is proposed, aimed at enhancing the bifunctional electroactivities of NiFe ₂ O ₄ toward the oxygen/hydrogen evolution reaction (O/HER) through the incorporation of MoS ₄ ²⁻ ions. Studies show that the S ²⁻ ligands in MoS ₄ ²⁻ act as H adsorption sites with optimized adsorption energy, while the Mo ⁶⁺ ‐mediated electronic regulation of Ni/Fe active sites reduces the H ₂ O dissociation energy, jointly boosting HER performance effectively. Moreover, MoS ₄ ²⁻ drives controlled reconstruction: accelerates formation of defect‐rich MoO ₄ ²⁻ /SO ₄ ²⁻ modified‐NiOOH layer during OER to activate the lattice oxygen mechanism (LOM), and d‐π conjugation inhibits over‐oxidation/leaching of metal ions to enhance OER stability. Benefiting from the dual regulatory effects of MoS ₄ ²⁻ , the NiFe ₂ O ₄ /MoS ₄ /NF shows a substantial enhancement in performance, with low overpotentials of 200 and 290 mV for HER and OER at 0.2 A cm ⁻² , respectively, as well as high stability (140 h at 0.5 A cm ⁻² ). Furthermore, when NiFe ₂ O ₄ /MoS ₄ /NF electrodes are employed as both the cathode and anode in an overall water splitting system, they can achieve 1.0 A cm ⁻² at 2.0 V. This research significantly expands the methodologies for the preparation of spinel oxide‐based bifunctional catalysts.