Reconstruction of Ferromagnetic/non‐magnetic Cobalt‐based Electrocatalysts under Gradient Magnetic Fields for Enhanced Oxygen Evolution

The rational manipulation of the surface reconstruction of catalysts is a key factor in achieving highly efficient water oxidation, but it is a challenge due to the complex reaction conditions. Herein, we introduce a novel in situ reconstruction strategy under a gradient magnetic field to form highly catalytically active species on the surface of ferromagnetic/non‐magnetic CoFe2O4@CoBDC core‐shell structure for electrochemical oxygen evolution reaction (OER). We demonstrate that the Kelvin force from the cores’ local gradient magnetic field modulates the shells’ surface reconstruction, leading to a higher proportion of Co2+ as active sites. These Co sites with optimized electronic configuration exhibit more favorable adsorption energy for oxygen‐containing intermediates and lower the activation energy of the overall catalytic reaction. As a result, a significant enhancement in OER performance is achieved with a large current density increment about 128% at 1.63 V and an overpotential reduction by 28 mV at 10 mA cm‐2 after reconstruction. Interestingly, after removing the external magnetic field, the activity could persist for over 100 h. This work showcases the directional surface reconstruction of catalysts under a gradient magnetic field for enhanced water oxidation.