Enhancing Photoelectrochemical\nWater Oxidation Using\nFerromagnetic Materials and Magnetic Fields

Photoelectrochemical (PEC) water splitting provides a\npromising\nstrategy for H<sub>2</sub> production. However, its performance is\nlimited by severe carrier recombination and sluggish water oxidation\nkinetics. While numerous strategies, namely, elemental doping, morphology\nengineering, heterojunction formation, and catalyst modification,\nhave been extensively explored to enhance the PEC performance, the\napplication of external magnetic fields (MFs) to affect the catalysis\nor charge carrier dynamics remains yet to be exploited. Herein, BiVO<sub>4</sub> is first selected as a representative photoanode, demonstrating\nthat an ultrathin ferromagnetic coating based on Fe<sub>2</sub>TiO<sub>5</sub>, when combined with an external MF, boosts its solar water\noxidation performance. The combined analyses of the charge transfer\nand separation efficiency together with ultraviolet photoelectron\nspectroscopy and transient absorption spectroscopy data revealed that\nthe MF positively affects the band alignment across the BiVO<sub>4</sub>/Fe<sub>2</sub>TiO<sub>5</sub> interface, improving the charge separation,\nwhile the oxygen evolution at the Fe<sub>2</sub>TiO<sub>5</sub>/electrolyte\ninterface was promoted. Finally, we expand this concept to other metal\noxide photoanodes, such as TiO<sub>2</sub>, WO<sub>3</sub>, and Fe<sub>2</sub>O<sub>3</sub>, demonstrating the universality of such an approach.\nOverall, this work pioneers a novel route to harvest external MFs\nand improve the PEC response of common nonmagnetic semiconductor photoelectrodes\nin photoelectrocatalytic conversion.