Magnetic field assisted electrocatalytic oxygen evolution reaction of nickel-based materials

Magnetic field-assisted electrocatalysis has recently been discovered as an effective approach to significantly improving the catalytic activity in various electrochemical reactions. However, the relevant promotional mechanism remains unclear. Here, we investigated the oxygen evolution reaction (OER) behaviors of nickel-based catalysts (Ni(OH)2, NiO, and Ni) under an in situ applied magnetic field, by using a self-designed electrochemical system coupled with a vibrating sample magnetometer that can fine-tune the intensity of the magnetic field (0-1.4 T). It is revealed that the magnetoresistance (MR) effect caused by spin electron scattering is dominant in affecting the apparent electrocatalytic activity (in terms of overpotential) in the magnetic field-assisted OER process. Notably, the magnetic field-induced spin-polarized kinetics will be more distinct in the case that the first electron transfer step is the rate-determining step of the OER. As a result, the magnetic field assisted OER activity can be most enhanced for Ni (the overpotential to deliver a current density of 10 mA cm-2 can be reduced by 20 mV at 1.4 T). Besides, the magnetohydrodynamic (MHD) effect caused by the Lorentz force, and charge transfer effect at the electrode/electrolyte interface are very likely for all catalysts. These discoveries may emerge as an essential and comprehensive understanding of the magnetic field-involved electrochemical reactions and help in the rational design of "magnetic effect"catalysts.