Magnetic field modulation of high spin hexa-coordinated iron sites to enhance catalytic activity

The external alternating magnetic field (AMF) strategy is the most promising research topic to solve the bottleneck of catalyst activity enhancement. However, the mechanism between the arrangement of the spin electrons under the AMF and the catalytic activity enhancement for water splitting is still unclear. Herein, we synthesize Fe3O4@CNTs heterostructure as a research model and resolve the mechanism by system theoretical analysis and in-situ Raman characterization. The multiple orbital interactions of σ(dz2, pz, s) and π(dxz-px, dyz-py) promote the hexa-coordinated Feoct for both the reductive HER and oxidative OER processes. The AMF excites the transition from low to high spin configurations of the Feoct sites, which accelerates charge transfer of unpaired d electrons and optimizes adsorption and desorption interactions to intermediates during the reaction processes, resulting in a significant enhancement of the electrocatalytic activity (HER: 32 mV at 10 mA cm-2, OER: 179 mV at 100 mA cm-2).