Magnetic-Field-Induced Electrochemical Performance of a Porous Magnetoplasmonic Ag@Fe3O4 Nanoassembly

The Lorentz or Kelvin force generated by an externally applied magnetic field may introduce additional convection of the electrolyte near the working electrode and consequently produces magnetocurrent (MC), which can be attributed to the magnetohydrodynamic (MHD) flow and an extra electrochemical reaction. A magnetoplasmonic (MagPlas) composite of metallic and superparamagnetic nanoparticles (NPs) with a permanent dipole or magnetic moment have additional degree or order, which corresponds to directional correlation to electric and magnetic dipoles. In particular, an ordered self-assembly may boost up the MHD flow on a collectively reactive surface, leading to remarkable electrochemical performance. In this article, a proof-of-concept work explores the effect of the magnetic field on the electrocatalytic activity of the oxygen reduction reaction (ORR) as well as [Fe(CN)(6)](3-/4-) redox probes using a precisely controlled three-dimensional (3D) nanostructure of a silver core and a porous magnetic shell (Ag@Fe3O4) assembly. Then, the reduction current was carefully monitored in the presence of a magnetic field (B, up to 380 mT), resulting in an extraordinary increment of reduction current (I-R) of [Fe(CN)(6)](3-) by 23% and a 1.13-fold high ORR efficiency owing to the additional magnetic field (B-in) from the 3D magnetoplasmonic nanoassembly. The computational simulation explained the plausible mechanism of current enhancement from the MagPlas nanoassembly. From our experimental and computational studies, it is probable that the 3D MagPlas nanoassembly is a unique and efficient catalyst under a low external magnetic field, which would be useful for further biomedical and energy-related applications.