Magnetic field-induced orientation alignment enhances the alkaline oxygen evolution reaction performance of NiFe2O4

Oriented NiFe 2 O 4 on carbon paper under a vertical magnetic field. • Vertical orientation structure improves ion transport, boosting catalytic performance. • Oriented catalyst exhibits 238 mV overpotential at 10 mA cm⁻² and 100 h stability. • Vertical alignment enhances OH⁻ adsorption and intermediate conversion. Magnetic field assistance is a novel strategy that can enhance the catalytic performance of OER. However, the mechanism by which it regulates the catalytic reaction remains unclear. In this study, nickel-ferrite (NiFe 2 O 4 ) was prepared by the hydrothermal method, and external magnetic fields in different directions (parallel or perpendicular to the electrode surface) were applied during its curing process, thereby preparing catalytic materials with different orientations. In 1 M KOH, the vertically oriented catalyst (NFO/CP-Pe) exhibited an OER overpotential of 238 mV at a current density of 10 mA cm −2 , which was 59 mV lower than that of the non-oriented sample. Moreover, its Tafel slope decreased to 57.58 mV dec −1 , and the charge transfer resistance was significantly reduced to 1.24 Ω, indicating that this orientation optimized the ionic transport channels. Meanwhile, Chronopotentiometry confirmed that the catalyst maintained excellent stability even after more than 100 h of use. This result can be attributed to the preferential arrangement along the (311) and (400) crystal planes in the vertically oriented samples, which forms ordered ion transport channels, thereby enhancing the electrochemical kinetics performance of the electrode. The in-situ tests demonstrated that the vertically-oriented NiFe 2 O 4 catalyst significantly enhanced the oxygen evolution reaction (OER) catalytic activity by pre-adsorbing OH⁻ and optimizing the evolution pathways and surface adsorption behaviors of key intermediates such as NiOOH and OOH*. Magnetically aligned NiFe 2 O 4 electrodes combine enhanced OER activity with long-term stability, confirming the efficacy of magnetic-field-assisted electrode construction and providing a promising route for orientation-controlled catalyst design. Download: Download high-res image (173KB) Download: Download full-size image