Enhancement of PGM-free oxygen reduction electrocatalyst performance for conventional and enzymatic fuel cells: The influence of an external magnetic field

Electrocatalysis can be enhanced either by using more active catalysts or by means of external process intensifications exploiting different energy types. The improvement of oxygen reduction reaction (ORR) efficiency by using an external magnetic field is technologically practical yet poorly scrutinized. An iron/nitrogen/sulfur-co-doped carbon gel (Fe-N-C/S) is studied as a non-precious metal catalyst for the ORR under an external magnetic field generated by a permanent magnet. The application of a magnetic field enhances the ORR process in both acidic and alkaline environments and yields higher selectivity towards 4e− electroreduction of O2. To elucidate the origin of the observed phenomena and show the role of the catalyst’s components, samples either free of sulfur (Fe-N-C) or iron (N-C/S) are studied as references. Moreover, the highly porous carbon gel constitutes an attractive substrate for enzyme immobilization. Modification of the catalyst with laccase (a multicopper oxidase enzyme) additionally strengthens the efficiency of O2 electroreduction.