Binary transition metal doping to create efficient TM–N–C electrocatalysts and enhance ORR catalysis under an external magnetic field

A family of bimetallic oxygen reduction catalysts was prepared from N-containing porous synthetic polymers doped with iron chloride and with the chloride of either Cr, Mn, Co, Cu or Zn. The effects of Fe interaction with the additional transition metal and their magnetic characteristics on the catalytic activity in the oxygen reduction reaction (ORR) in alkaline medium were investigated. In addition, the ORR catalyzed by these bimetallic non-precious metal catalysts was studied under an external magnetic field generated by a permanent magnet. Linear sweep voltammetry in stationary conditions showed that the Co co-doped catalysts exhibit the highest activity, strongly enhanced by an external magnetic field applied at a 90° angle relative to the catalyst layer surface. Rotating ring-disk electrode tests (at pH = 13) showed that catalysts co-doped with either Mn or Zn exhibit the highest catalytic activity. In these instances, an external magnetic field decreases the amount of undesirable peroxide intermediate as it increases the number of electrons transferred for ORR.