Enhanced Transport and Electrocatalysis in External Magnetic Field

Recently we have turned to a new material for modification of glassy carbon electrodes: carbon nanocapsules with iron core (C-Fe). The carbon coating plays an important role; it separates the magnetic nanoparticle from the medium, protects it against oxidation and dissolution and adsorbs strongly on GC surface. C-Fe nanocapsules appeared to be a useful surface modifier. We have found that the adsorption of the nanocapsules on the GC electrode surface led to a shift of the reduction voltammetric peak/wave of oxygen by more than 200 mV toward less negative potentials. After applying an external magnetic field in the cell a substantial increase in the reduction current was observed. Similar increase of current was noted for ferroceneacetate anion, a paramagnetic molecule.

The C-Fe nanocapsule layer appeared also to be a good matrix for immobilization of laccase. The presence of laccase on the electrode surface modified with carbon nanocapsules caused an additional significant shift, compared to the C-Fe layer, of the position of the oxygen reduction signal toward positive potentials. The application of an external magnetic field led again to a strong increase in the reduction current. We have characterized the effect in function of the magnetic field intensity, the angle between the electrode surface and the magnetic field direction and the concentration of the substrate.

The application of magnetic field apparently helped to get appropriate orientation of the immobilized laccase at the surface. The high efficiency of electroreduction of oxygen was maintained after removal of the magnets.

The significant enhancement of dioxygen reduction current was compared with the simulations. For this purpose the profile of the magnetic field in the neighborhood of the electrode surface was constructed and the force of interactions of paramagnetic oxygen molecules with magnetic nanoparticles was calculated.