Magnetic field-induced surface reconstruction of Fe-CoP nanostructures for enhanced oxygen evolution catalytic performance

Abstract

In this study, a static magnetic field-assisted electrodeposition strategy (600 mT) was employed to prepare Fe-CoP nanoclusters as oxygen evolution reaction (OER) catalysts. This strategy significantly accelerated the deposition process and optimized the initial stage of catalyst growth. In 1.0 M KOH, the initial overpotential of Fe-CoP-600 at 100 mA cm⁻² was 315 mV. A key finding was that during the OER process, applying an 800 mT vertical static magnetic field to the working electrode could significantly reduce the overpotential to 300 mV (a 15 mV decrease compared to the reaction without a magnetic field). Characterization (TEM and XPS) confirmed that the magnetic field triggered in situ dynamic reconstruction of the catalyst surface, generating abundant Fe-OOH sites and high-activity Co-OOH species (mainly CoP/Co³⁺ after the reaction without a magnetic field). By combining zero-field cooling (ZFC) magnetic susceptibility-temperature (M–T) curves and calculations, it was shown that the magnetic field induced the interface Fe³⁺ to change from a low-spin to a medium-spin state. This alteration in spin state, in synergy with surface reconstruction, tuned the electronic configuration and greatly heightened the OER catalytic activity. This study showed that magnetic field-assisted deposition effectively improved the preparation efficiency and optimized the initial state of the catalyst. Meanwhile, the static magnetic field applied during the reaction process, by inducing in situ surface reconstruction and regulating the spin state of Fe³⁺, was the key to dynamically optimizing the intrinsic performance of the catalyst.