Magnetic Field Enhancing the Electrocatalytic Oxygen Evolution Reaction of FeMn-Based Spinel Oxides

For the widespread application of electrolytic waterhydrogen productiontechnology, it is crucial to prepare electrolytic water catalystsvia inexpensive and abundant transition metals. Commercially, Mn3O4 can be utilized extensively since it is cheap,abundant, and stable, but its electrocatalytic performance still needsto be enhanced. In this paper, we adopted the conventional hydrothermalmethod to introduce Fe atoms into Mn3O4 to formspinel-structured FeMn oxides on Ni foam (marked as Fe x Mn3-x O4); then, an external magnetic field was applied to further improveits oxygen evolution reaction (OER) performance. The overpotentialof FeMn2O4 is 258 mV (current density at 20mA & BULL;cm(-2)), and the Tafel slope is 28.7 mV & BULL;dec(-1) when the magnetic field strength is 105 mT and theangle between the electric field and the magnetic field is 45 & DEG;.The introduction of Fe and the synergistic effect of the mixed Mnand Fe promote the reaction kinetics and thus improve the OER performanceof Mn3O4. The enhanced performance of Fe x Mn3-x O4 under the magnetic field may mainly originate from the magnetohydrodynamic(MHD) effect, charge transfer effect, and energy effect.