Carbon-supported tetragonal MnOOH catalysts for oxygen reduction reaction in alkaline media

Carbon-supported MnOOH catalyst was prepared by reducing KMnO4 with carbon Black Pearls 2000. TEM and XRD characterization results show that nanosized tetragonal MnOOH crystals formed in the specimen when the MnOOH content ranged from 9 wt.% to 36 wt.%. The oxygen reduction reaction (ORR) activity of the catalyst with different amounts of MnOOH content in alkaline media was investigated using a rotating disc electrode (RDE) and a rotating ring-disc electrode (RRDE). The number of electrons involved in the ORR increased from 3.2 to 3.9 with the increase of the MnOOH content from 9 wt.% to 36 wt.% in the catalyst. The kinetic current increased to 0.0184 A cm−2 when the MnOOH content was increased to 72 wt.%. However, both the number of electrons and the kinetic current decreased when the MnOOH content was increased from 72 wt.% to 90 wt.%. The MnOOH/C catalyst with optimized MnOOH content and suitable loading in the cathode is promising for applications in alkaline fuel cells.