Notions of Magnetoelectrocatalysis
Authors: Lee Heung Chan , Minteer Shelley D. , Leddy Johna 
Published: February 2020

Greater efficiency in reactions important to energy generation and storage has broad consequences beyond chemistry. Means to enhance reaction rates are typically by chemical manipulation of catalyst materials, but physical manipulation of reactions, as by temperature and pressure, is also effective. Here, means to increase reaction rates with magnetic fields and based on the magnetic properties of substrates and materials is considered.
For a wide range of reactions and device relevant to electrochemical energy and power, introduction of magnetic microparticles onto or into an electrode structure has been found to increase rates and to reduce the tax of overpotential1-18. This includes batteries3-6, fuel cells7-11, photoelectrochemical cells1, dye sensitized solar cells13, asymmetric supercapacitors13, hydride storage15, and alcohol electrolysis13,14. Relevant reactions include hydrogen evolution reaction (HER)1, hydride storage15, and CO oxidation8.
The basic notion is that electrons have properties of mass, charge, and spin. Spin interacts with the applied magnetic fields. To transfer an electron, it is necessary to transfer the spin and the charge. Application of a magnetic field should impact the rates of electron transfer. Experiments1-17 have shown that the rate of the reaction depends on the magnetic properties of the reactants and products as well as the strength of the applied magnetic field H or intensity B. Measured rates are highly correlated2 with the Zeeman energies in the system, Z = gSBb.
Detailed temperature studies for academically interested redox probes has allowed development of a model for magnetic effects on self exchange reactions1. The model modifies Marcus theory to allow split of the energy levels by the applied field, which has several impacts on rate. The only specific chemical information in Marcus theory is the size and charge of the redox probe and the dielectric constant of the medium. Consideration of the magnetic effects introduces additional magnetic properties into the model.
Here, several important energy relevant reactions are considered in light of the model. This includes the HER on several electrodes1, hydride storage in Pd15, and diffusion limited CO oxidation on Pt8. The impacts of the magnetic properties of the reactants and environment are discussed.
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