title: Pseudocapacitive hausmannite nanoparticles with (101) facets: synthesis, characterization, and charge-transfer mechanism.
abstract: Hausmannite Mn3 O4 octahedral nanoparticles of 18.3 ± 7.0 nm with (101) facets have been prepared by an oxygen-mediated growth. The electrochemical properties of the Mn3 O4 particles as pseudocapacitive cathode materials were characterized both in half-cells and in button-cells. The Mn3 O4 nanoparticles exhibited a high mass-specific capacitance of 261 F g(-1), which was calculated from cyclic voltammetry analyses, and a capacitive retention of 78% after 10,000 galvanostatic charge-discharge cycles. The charge-transfer mechanisms of the Mn3 O4 nanoparticles were further studied by using synchrotron-based in situ X-ray absorption near edge spectroscopy and XRD. Both measurements showed concurrently that throughout the potential window of 0-1.2 V (vs. Ag/AgCl), a stable spinel structure of Mn3 O4 remained, and a reversible electrochemical conversion between tetrahedral [Mn(II) O4 ] and octahedral [Mn(III) O6 ] units accounted for the redox activity. Density functional theory calculations further corroborated this mechanism by confirming the enhanced redox stability afforded by the abundant and exposed (101) facets of Mn3 O4 octahedra.
authors: Department of Chemical Engineering, University of New Hampshire, NH 03824 (USA).
authors: Matthew P
authors: MP
authors: Yeager
authors: Wenxin
authors: W
authors: Du
authors: Qi
authors: Q
authors: Wang
authors: N Aaron
authors: NA
authors: Deskins
authors: Matthew
authors: M
authors: Sullivan
authors: Brendan
authors: B
authors: Bishop
authors: Dong
authors: D
authors: Su
authors: Wenqian
authors: W
authors: Xu
authors: Sanjaya D
authors: SD
authors: Senanayake
authors: Rui
authors: R
authors: Si
authors: Jonathan
authors: J
authors: Hanson
authors: Xiaowei
authors: X
authors: Teng
mesh_terms: D004563:Electrochemistry; D004579:Electron Transport; D017895:Manganese Compounds / Q000737:chemistry*; D008958:Models, Molecular; D008968:Molecular Conformation; D053758:Nanoparticles / Q000737:chemistry*; D010087:Oxides / Q000737:chemistry*
chemical_list: D017895:Manganese Compounds; D010087:Oxides; C027424:manganese oxide
keywords: X-ray absorption spectroscopy; X-ray diffraction; manganese; redox chemistry; supercapacitors