The origin of magnetic field enhanced oxygen evolution reaction performance of single/multi-domain catalysts

The sluggish kinetics of the oxygen evolution reaction (OER) at the anode of water electrolysis constrains the overall energy conversion. The design of efficient electrocatalysts can significantly reduce the reaction overpotential. Due to the distinct spin states of adsorbed oxygen intermediates and products, ferromagnetic catalysts facilitate spin-polarized electron transfer under an applied magnetic field, thereby accelerating OER kinetics. In this work, the non-magnetic Zn²⁺ was incorporated into NiFe₂O₄, effectively modulate the magnetic properties and magnetic domain structures of the catalysts. The effect of magnetic field on multi-domain catalysts (NiFe₂O₄) is more pronounced, whereas the magnetic response of single-domain catalysts (Ni_1-xZn_xFe₂O₄) can be enhanced by optimizing their intrinsic magnetic properties. Theoretical calculations demonstrate that the evolution process of magnetic domain walls in multi-domain catalysts under a magnetic field may result in alterations to the active sites at the magnetic domain walls regions. Single-domain catalysts which lack magnetic domain walls exhibit enhancement effects that originate from the magnetic field's modulation of the electronic states at active sites. These findings provide insights into understanding the OER effect of magnetic field-enhanced single or multi-domain catalysts.