Unraveling role of double-exchange interaction in electrochemical water oxidation by external magnetic field

Double-exchange (DE) interaction plays an important role in electrocatalytic oxygen evolution reaction (OER). However, precise achievement of DE interaction often requires foreign dopants or vacancy engineering, leading to destabilization of the catalysts and deterioration of performance. By contrast, the utilization of environmentally friendly, contactless, and continuously adjustable magnetic fields to study the OER process is profitable to avoid aforementioned interference factors and further elucidate the direct relationship 0.5 between DE interaction and OER activity. Here, by using cobalt hydroxide carbonate (Co(OH)(CO 3 )· x H 2 O, CoHC) nanostructures as a proof-of-concept study, external magnetic fields are carefully implemented to verify the role of DE interaction during water oxidation reaction. Detailed studies reveal that external magnetic fields effectively enhance the reaction rate of the catalyst, the overpotential decreases from 386 to 355 mV (100 mA·cm −2 ), while Tafel slopes drastically decline from 93 to 67 mV·dec −1 (1.0 T). Moreover, magnetic field increment exhibits robust durability. Through in situ Raman and impedance measurements under external field, it can be found that magnetic field promotes the electron migration between Co 2+ and Co 3+ in the CoHC catalysts with the assistance of DE interactions, thus boosting the OER efficiency. Graphical abstract