Oxygen vacancies engineering in iron-doped nickel molybdate nanorods to accelerate electron transfer for rapid organic pollutants removal

Iron-doped metal oxides have been widely used in Fenton-like reactions. However, sluggish conversion of Fe³⁺/Fe²⁺ circulation for inevitably forming iron sludge limits its applications. Herein, Fe-doped NiMoO nanorods with heteroatomic metal sites and rich oxygen vacancies (O_v) were prepared for the first time as novel heterogeneous catalysts (Ni/FeNi₃-NiMoO). The Ni/FeNi₃-NiMoO could rapidly degrade organic pollutants including tetracycline, bisphenol A, ciprofloxacin, sulfamethoxazole, and rhodamine B in 5 min via peroxymonosulfate (PMS) activation. The Ni/FeNi₃-NiMoO nanorods achieved a remarkable catalytic rate constant of 0.482 min⁻¹, which was 371-fold higher than that of NiMoO and surpassed previously reported Fe-based catalysts. Besides, the Ni/FeNi₃-NiMoO membrane reactor exhibited good adaptability, durability over 10 h, and efficient organic pollutants oxidation capacity. Hydroxyl radical was the primary reactive oxygen species by quenching experiments and electron paramagnetic resonance, which contributed 79.3% in the Ni/FeNi₃-NiMoO/PMS system. A catalytic mechanism verified that the synergistic effect of Mo/Ni sites and rich O_v promoted the electron transport speed for a rapid Fe³⁺/Fe²⁺ cycle to boost PMS activation. This work provides valuable insights into Fe-doped metal oxides for accelerating the Fe³⁺/Fe²⁺ cycle in Fenton-like reactions.