Deposition of Iron Doped Birnessite during Simultaneous Electroreduction of Permanganate and Ferrate(VI) in Sodium Hydroxide Solution

The reduction of permanganate on a rotating disk electrode is accompanied by an inhibition of depositing birnessite. The addition of potassium ferrate(VI) leads to an increase of inhibition. The obtaining of electrode material based on Fe-doped birnessite under alkaline conditions is demonstrated in experiment with deposition at inhibition potentials. This birnessite is single phase and highly disordered. The Fe content varies from 0 to 10 mol % in respect to Mn with increasing ferrate(VI) content in deposition solution. Recharging potentials of birnessite are shifted which is manifested by cyclic voltammetry. Doping allows to increase the rate of oxygen evolution reaction. The specific currents increase with the iron content in birnessite. The Tafel slope is 53 mV/dec and by 2.5 times lower for birnessite containing 10 mol % Fe.