Modulation of the Phase Transformation of Fe<sub>2</sub>O<sub>3</sub> for Enhanced Water Oxidation under a Magnetic Field
Guangjian Song, Ming Wei, Jing Zhou, Liuhua Mu, Sanzhao Song
Abstract
Ferromagnetic catalysts in the presence of an external magnetic field can promote the reaction kinetics of the oxygen evolution reaction (OER) by enhancing spin-selective electron transfer as intermediates and products confer spin-dependent behavior. It has been found that γ-Fe 2 O 3 with ferromagnetism exhibits an enhanced performance for the OER activity, but its preparation is limited. Herein, we report an adsorption-pyrolysis process in air in which the transformation of α-Fe 2 O 3 into γ-Fe 2 O 3 is precisely regulated by controlling the content of Co ions. Interestingly, a small, constant external magnetic field (∼200 mT) was applied at the anode, resulting in a significant impact on the OER performance of the obtained series of catalysts with different contents of γ-Fe 2 O 3 under alkaline conditions. Theoretical results reveal that the same spin configuration of Fe and O atoms in γ-Fe 2 O 3 provides a spin conduction channel, which enhances the ability to selectively remove spin-oriented electrons from the reactants and accelerates the accumulation of triplet oxygen molecules during the OER process, thereby promoting the OER. These findings provide a strategy toward the controllable phase transformation of Fe 2 O 3 and deep insights for understanding the OER behavior of Fe-based electrocatalysts under magnetic fields.