Photothermal-Magnetic Synergistic Effects in an Electrocatalyst for Efficient Water Splitting under Optical-Magnetic Fields.

Abstract

The slow oxygen evolution reaction (OER) limits water splitting, and external fields can help improve it. However, the effect of a single external field on the OER is limited and unsatisfactory. Furthermore, the mechanism by which external fields improve the OER is unclear, particularly in the presence of multiple fields. Herein, a strategy is proposed for enhancing the OER activity of a catalyst using the combined effect of an optical-magnetic field, and the mechanism of catalytic activity enhancement is studied. Under the optical-magnetic field, Co3 O4 reduces the resistance by increasing the catalyst temperature. Meanwhile, CoFe2 O4 further reduces the resistance via the negative magnetoresistance effect, thus decreasing the resistance from 16 to 7.0Ω. Additionally, CoFe2 O4 acts as a spin polarizer, and electron polarization results in a parallel arrangement of oxygen atoms, which increases the kinetics of the OER under the magnetic field. Benefiting from the optical and magnetic response design, Co3 O4 /CoFe2 O4 @Ni foam requires an overpotential of 172.4mV to reach a current density of 10mAcm-2 under an optical-magnetic field, which is significantly higher than those of recently reported state-of-the-art transition-metal-based catalysts.