Magnetic fluid-assisted CoFeNi/NF bifunctional electrocatalyst for high-efficiency water splitting in alkaline medium

Developing efficient bifunctional electrocatalysts is vital for scalable hydrogen production via overall water splitting. Here, a magnetic-fluid-assisted CoFeNi–MF/NF catalyst was synthesized through a two-step hydrothermal process by integrating Fe₃O₄-based magnetic fluid into vertically aligned CoFeNi nanosheets on nickel foam. Structural analyses confirmed the formation of an FCC CoFeNi alloy coupled with spinel Fe₃O₄, creating an interconnected architecture with abundant active sites. Magnetic-fluid incorporation enhanced charge transfer, oxygen content, and electron/spin polarization, enabling faster catalytic kinetics.  In 1.0 M KOH, CoFeNi–MF/NF delivered low overpotentials of 169 mV for HER and 199 mV for OER at 10 mA·cm⁻², along with Tafel slopes of 133.09 and 91.41 mV·dec⁻¹. The catalyst also showed low charge-transfer resistance and enlarged electrochemically active surface area. Durable operation at 100 mA·cm⁻² for 24 h further confirmed its stability. This work presents a promising strategy for designing magnetic-responsive, non-noblemetal electrocatalysts for alkaline water splitting.

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