title: Correlation among physical and electrochemical behaviour of nanostructured electrolytic manganese dioxide from leach liquor and synthetic for aqueous asymmetric capacitor.
abstract: An attempt has been made to correlate the differences in structural parameters, surface areas, morphology etc. with the electrochemical capacitive behaviour of the EMDs. The nanostructured electrolytic manganese dioxides (EMD) have been synthesized through electrodepositing MnO2 from two different leach liquors and a synthetic analogue thereof. The structural and chemical state was determined using X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) respectively. Multiplet structure determination led to estimates of the manganese valence states present in the EMD. The EMDs have been tested in an asymmetric capacitor which we have developed. This used activated carbon as the negative electrode and the various EMDs as the positive electrode. Aqueous 2 M NaOH solution was used as the electrolyte. The capacitor achieved 1.6 V corresponding to a capacitance of ∼50 F g(-1) of the EMDs from leach liquors. The EMD derived from the synthetic solution showed an inferior capacitance of 25 F g(-1). Extended cycling (2000 cycles), showed 100% capacity retention was achieved for one EMD produced from the leach liquor derived from low-grade manganese ore/residue. This outstanding capacitor performance was correlated with the presence of a nanofibrous morphology. These findings open up the possibility of extracting a high performance EMD product from a low cost, low-grade source of manganese.
authors.affiliation: School of Engineering and Information Technology, Murdoch University, Murdoch, WA 6150, Australia. m-minakshi-sundaram@murdoch.edu.au.
authors.forename: Manickam
authors.initials: M
authors.lastname: Minakshi Sundaram
authors.affiliation: School of Engineering and Information Technology, Murdoch University, Murdoch, WA 6150, Australia. m-minakshi-sundaram@murdoch.edu.au and CSIR-Institute of Minerals and Materials Technology, Bhubaneswar 751013, Odisha, India.
authors.forename: Avijit
authors.initials: A
authors.lastname: Biswal
authors.affiliation: Electron Microscope Centre, Australian Institute for Innovative Materials, Innovation Campus, University of Wollongong, North Wollongong, NSW 2500, Australia.
authors.forename: David
authors.initials: D
authors.lastname: Mitchell
authors.affiliation: Centre for Materials and Surface Science, La Trobe University, Bundoora, VIC 3086, Australia.
authors.forename: Rob
authors.initials: R
authors.lastname: Jones
authors.affiliation: School of Pharmacy and Life Sciences, Robert Gordon University, Aberdeen AB10 7GJ, UK.
authors.forename: Carlos
authors.initials: C
authors.lastname: Fernandez