Characterization of spray pyrolyzed manganese oxide powders deposited by electrophoretic deposition technique

Nanocrystalline manganese oxide powders were prepared by spray pyrolysis (SP) from manganese acetate solution at 400 degrees C. The as-obtained powders were subsequently coated onto graphite substrates via an electrophoretic deposition technique (EPD). The as-prepared powders were examined by transmission electron microscopy (TEM), X-ray diffractometry (XRD), synchrotron X-ray absorption spectroscopy (XAS); the coatings were further examined by cycling voltammetry (CV). Experimental results showed that manganese oxide powders prepared at 400 degrees C were hollow spherical particles with fractured shells and possessed high surface area. CV examination showed that the as-deposited coatings also exhibited the highest specific capacitance of 275 F/g. After hundreds of CV cycles, the specific capacitance decreased to 234 F/g, which was still comparable to values reported in the literature. Structural investigation by TEM and XRD revealed that the as-deposited coatings exhibited Mn3O4 phase with amorphous-like structure. While synchrotron XAS results showed that the manganese had a valence of +2.67, it was transited into tetravalent manganese after cyclic voltammetry. (C) 2007 Elsevier B.V. All rights reserved.