Table sugar as preparation and carbon coating reagent for facile synthesis and coating of rod-shaped MnO2

Rod-shaped α-MnO2 has been synthesized by a novel and facile wet chemical method using simple sugar and potassium permanganate. Redox reaction between KMnO4 and sucrose is carried out in an acidic medium. Acidic medium provides a reducing character to sucrose through its decomposition to elemental carbon. Carbon coating process was done using simple sugar also as a source for carbon in an absolute ethanol with heating the mixture of α-MnO2 and sugar at 350 °C for an hour in an ambient atmosphere. A single phase of cryptomelane-like phase MnO2 was observed from XRD patterns for bare and carbon coated samples. TGA analysis shows the presence of carbon layer through more weight loss percent of carbon coated sample in comparison with that of carbon free MnO2. Both virgin and carbon coated MnO2 have high thermal stability due to high percent of K inside the tunnel determined from ICP analysis. Transmission Electron Microscope (TEM) showed a rod-shaped crystal for both the parent and carbon coated α-MnO2 and confirmed the presence of a thin film of carbon around MnO2 particles. Both XRD and TEM investigations show that the prepared powders are in nano-scale. Initial capacity of about 140 mAh/g was obtained for the parent and carbon coated samples. The results show also that carbon coating process improves the capacity retention and the efficiency of α-MnO2 in comparison with that carbon free sample.