Isolated Mo-doped nickel-iron spinel catalyst with oxygen vacancy and high-density interfaces for oxygen evolution reaction

Heteroatom doping combined with oxygen vacancy introduction serves as an effective strategy to tailor the electronic structure of the catalyst, enhancing their electrocatalysis activity and reducing overpotential. In this study, isolated Mo-doped nickel-iron spinel oxygen evolution reaction (OER) catalysts were synthesized using molybdenum pentachloride (MoCl₅) as the molybdenum source. In the synthesis process, Mo participates in the reaction as a free ion and facilitate the formation of high-density interfaces. And the electronic structure of the catalysts was further adjusted by introducing oxygen defects through chemical reduction with NaBH₄, leading to a considerable boost in OER catalytic activity. The incorporation of Mo can enhance the oxidation states of nickel and iron, promotes the conversion of oxides into electrochemically active species in the electrocatalytic process. Additionally, Mo doping optimized the OER reaction pathway. The prepared MNFO-V_O catalyst demonstrated excellent performance, attaining current densities of 10 mA cm⁻² with overpotentials of only 315 mV. Furthermore, MNFO-V_O achieved 1 A cm⁻² at 1.73 V in an anion exchange membrane water electrolyzer (AEMWE) and maintained stable performance for 100 h. Our catalyst design concept shows valuable guiding for advancing the application of nickel-iron based oxide OER catalysts in water electrolysis.