Controllable fabrication of δ-MnO2 microspheres and α-MnO2 nanorods

MnO2 nanostructure was synthesized via a redox reaction of potassium permanganate in hydrochloric acid solution below 100 degrees C at open environment. The effects of pH value in solution and reaction temperature on the crystal structure and morphology of MnO2 were investigated. It was revealed that layer folded delta-MnO2 microspheres were obtained at low reaction temperature and low HCl concentration, whereas alpha-MnO2 single-crystal nanorods were fabricated with increasing reaction temperature and HCl concentration. The possible formation mechanism of delta-MnO2 microspheres and alpha-MnO2 nanorods is suggested.