Synthesis of Manganese Oxide Microspheres by Ultrasonic Spray Pyrolysis and Their Application as Supercapacitors

Yinan Zhang, Laura A. Huff, Andrew A. Gewirth, Kenneth S Suslick

Research output: Contribution to journalArticlepeer-review

Abstract

Manganese oxide (MnO2) microspheres are prepared using an ultrasonic spray pyrolysis (USP) process. A mixed solution of potassium permanganate and hydrochloric acid is nebulized into microsized droplets, which are then carried by air flow through a furnace tube. Each microdroplet serves as one microreactor and produces one microsphere. Upon heating, KMnO4 is decomposed into MnO2 microspheres; this synthetic process can easily be scaled up. Characterization of the MnO2 microspheres by scanning electron microscopy, transmission electron microscopy, powder X-ray diffraction, Raman spectroscopy, and X-ray photoelectron spectra is described. Different morphologies of MnO2 microspheres can be controlled by tuning the precursor concentrations (and ratios) and furnace temperatures. Microspheres synthesized at 150 °C give amorphous MnO2 while synthesis at 500 °C yields crystalline α-MnO2. The electrochemical properties investigated by cyclic voltammetry give specific capacitance as high as 320 F g-1, demonstrating promising properties as supercapacitors. In addition, these microspheres can be directly sprayed on conductive substrates, such as carbon fiber paper, and may have useful applications as a supercapacitor electrode coating. The supercapacitive properties of MnO2 microspheres at higher charge and discharge rates can be improved by increasing the surface area coverage or coating them with a thin layer of conductive polymer.

Original languageEnglish (US)
Pages (from-to)899-906
Number of pages8
JournalParticle and Particle Systems Characterization
Volume32
Issue number9
DOIs
StatePublished - Sep 1 2015

Keywords

  • manganese dioxide
  • microspheres
  • supercapacitors
  • ultrasonic spray pyrolysis

ASJC Scopus subject areas

  • General Chemistry
  • General Materials Science
  • Condensed Matter Physics

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