Magnetic Field Enhanced Electrocatalytic Oxygen Evolution of NiFe-LDH/Co 3 O 4 p-n Heterojunction Supported on Nickel Foam.

Here, a strategy to regulate the electron density distribution by integrating NiFe layered double hydroxides (NiFe-LDH) nanosheets with Co 3 O 4 nanowires to construct the NiFe-LDH/Co 3 O 4 p-n heterojunction supported on nickel foam (NiFe-LDH/Co 3 O 4 /NF) for electrocatalytic oxygen evolution reaction (OER) is proposed. The p-n heterojunction can induce the charge redistribution in the heterogeneous interface to reach Fermi level alignment, thus modifying the adsorption free energy of *OOH and improving the intrinsic activity of the catalyst. As a result, NiFe-LDH/Co 3 O 4 /NF exhibits outstanding OER performance with a low overpotential of 274 mV at a current density of 50 mA cm -2 and long-time stability over 90 h. Moreover, NF can serve as a magnetic core that induces the exchange bias effect between the magnetic substrate and the active species under the action of the magnetic field, resulting in decreased magnetoresistance and weakened scattering of spin electrons, which further lowers the OER overpotential by 25 mV @ 50 mA cm -2 under a 10 000 G magnetic field. This work provides a new perspective on the design of p-n heterojunction catalysts and a deeper understanding of the magnetic field-enhanced electrocatalytic reactions.