Electrochemical properties of δ- and γ-MnO2 thin films deposited by a chemical bath technique

In this study, γ- and δ-MnO2 thin films were deposited onto F-doped tin oxide glass substrates via a chemical bath deposition technique in which manganese (II) ions were oxidized by bromate ion in a homogeneous solution. The addition of cetyltrimethylammonium chlorate to the starting solutions resulted in the deposition of the δ-phase. The thin films showed rectangular cyclic voltammograms even at higher scan rates. The δ-phase films showed better specific capacitance than the γ-phase films. A 200-nm-thick δ-MnO2 film showed an excellent specific capacitance of 750 F/g at a scan rate of 10 mV/s.