Synthesis and characterization of nanostructured magnetite and magnetite/carbon nanocomposite thin films for electrochemical applications

Stable colloidal suspensions of magnetite and magnetite/starch nanocomposite prepared by the co-precipitation method, and a simple, facile and aqueous-based chemical precipitation method, respectively. Nanoparticulate magnetite thin films on supporting stainless steel plates were prepared by drop-coating followed by heat treatment under controlled conditions (Fig. 1). The effects of calcination temperature and atmosphere on the microstructure and electrochemical properties of nanoparticulate magnetite thin films were investigated. Magnetite/carbon nanocomposite thin films were formed from the magnetite/starch nanocomposites after the starch component was carbonized by heat treatment under controlled conditions (Fig. 1). The initial content of native sago starch was found to affect the microstructure and electrochemical properties of the resulting magnetite/carbon nanocomposite thin films (Fig. 2). Nanoparticulate magnetite thin films prepared under optimized conditions exhibited a specific capacitance value of 82 F/g in mild aqueous solution of 1.0 M Na2SO4 (Fig. 3). A specific capacitance of 124 F/g was achieved for the magnetite/carbon nanocomposite thin films in the same mild aqueous electrolyte. Due to their high charge capacity, good cycling reversibility and stability in a mild aqueous electrolyte, nanoparticulate magnetite and magnetite/carbon nanocomposite thin films appear to be very promising electrode materials for the fabrication of charge-storage devices, in particular, electrochemical capacitors.