Strain-Induced Magnetic Modulation of NiCo2O4 for Magneto-Electrochemical Oxygen Evolution
a NanoSYD, Mads Clausen Institute, University of Southern Denmark, Alsion 2, DK-6400 Sønderborg, Denmark
Improvement of the efficiency and cost-effectiveness of the oxygen evolution reaction (OER) remains a major challenge in water electrolysis due to its complex thermodynamics and sluggish four-electron kinetics, which involve generating paramagnetic O2 from diamagnetic species (H2O, OH–). Recent studies have demonstrated that tuning the magnetic state of catalysts or applying external magnetic fields can significantly impact reaction pathways in spin-dependent processes. [1] In this work, we present magnetically modulated NiCo2O4 as an anode catalyst for magneto-electrocatalytic (MAG-EC) OER in alkaline media. By introducing strain into NiCo2O4 by rapid quenching in liquid nitrogen, the magnetic moment at room temperature was enhanced by ~18%. Under a low external magnetic field of 0.32 T, strained-NiCo2O4 exhibited a 12.6% decrease in overpotential at 10 mA∙cm–2, compared to only a 3% reduction for pristine NiCo2O4 under identical conditions. Additionally, strained NiCo2O4 exhibited a remarkable 125.8% enhancement in current density (geometric) at 1.68 V vs. RHE under a 0.32 T magnetic field in comparison to that obtained without applying a magnetic field. These enhancements achieved by applying a magnetic field are attributed to increased spin polarization in the ferrimagnetic catalyst arising from its strengthened magnetic moment. The results highlight a conceptual advancement in magnetically controlled electrocatalysis, demonstrating how strain engineering and magnetic-state modulation can significantly boost OER activity. The insights gained from this study may guide the future design of spin-regulated catalytic materials for a broad range of energy conversion reactions.