Electrophoretic deposition of manganese oxide films

Electrophoretic deposition method has been developed for the fabrication of manganese oxide films for applications in electrochemical supercapacitors. Submicrometre particles of manganese oxide were obtained by reduction of KMnO4 solutions with ethanol. As prepared particles were amorphous and crystallised in a birnessite structure after annealing at 400 degrees C during 1 h. The use of sodium alginate as a dispersant, enabled electrosteric stabilisation of the nanoparticles in aqueous suspensions. It was shown that binding properties and pH dependent charge of alginate enabled electrophoretic deposition of crack free films. The thickness of the films prepared from stable suspensions, containing 1-10 g L-1 manganese oxide, was varied in the range of 2-100 mu m by variation in deposition time and applied voltage. The composition of the films can be varied by the variation in suspension composition. Cyclic voltammetry and chronopotentiometry data for the films tested in the 0.1M Na2SO4 solutions showed capacitive behaviour in the voltage window of 0.9 V. The highest specific capacitance of similar to 150 F g(-1) was obtained at a scan rate of 2 mV s(-1). The deposition mechanism, kinetics of deposition and charge storage properties of the films are discussed.