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Abstract: One-dimensional manganese (IV) oxide (MnO2) (∼20nm in average diameter) were synthesized by cathodic electrodeposition and heat treatment. The mechanism of electrodeposition and nanowire formation were discussed. The product was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Fourier transform infrared (FT-IR). Nanowires with varying lengths and diameters were found in TEM and SEM images of the sample. The results of N2 adsorption–desorption analysis indicated that the BET surface area of the MnO2 nanowires was 157m2 g−1 and the pore size distributions were 2.5 and 4.5nm. The electrochemical performances of the prepared MnO2 as an electrode material for supercapacitors were evaluated by cyclic voltammetry and galvanostatic charge/discharge measurements in a solution of 0.5M Na2SO4. The higher specific capacitance of 318Fg−1 and good capacity retention of 86% were achieved after 1000 charge–discharge cycles had been observed for the MnO2 nanowires electrode. [Copyright &y& Elsevier]

Abstract: The dense manganese oxide nanorods with an extremely narrow distribution are synthesized at a low temperature using first cathodic electrodeposition subsequently heat treatment. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images show that the nanorods have bar shapes, and their average diameter is less than 50nm. The Fourier transform infrared (FT-IR) study, the selected area electron diffraction (SAED) pattern in TEM images and the X-ray diffraction (XRD) result show that the nanorods are α-MnO2 single crystal. The results of N2 adsorption–desorption analysis indicate that the BET surface area of the α-MnO2 nanorods is 93m2 g−1. By recording the potential–time curve during the electrodeposition process, it is revealed that water reduction reaction has a major role in the electrogeneration of base at the cathode surface under the applied electrochemical conditions. Finally, based on the H2 bubbling on the cathode surface, the mechanism of the formation and the growth of α-MnO2 nanorods are proposed and discussed. For the electrochemical supercapacitor application, electrochemically prepared α-MnO2 is found to be stable for a large number of cycles with high specific capacitance, 338Fg−1 at a scan rate of 10mVs−1. Finally, the charge–discharge mechanism is discussed. [Copyright &y& Elsevier]

Abstract: Uniform and single-crystalline Mn3O4 nano-spheres were synthesized by cathodic electrodeposition at high temperature (80 °C) and low current density (0.25 mA cm−1) on steel electrode. Further the annealed samples were characterized for their structural and morphological properties by means of X-ray diffraction (XRD), Fourier transform infrared spectrum (FTIR), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM) and Brunauer-Emmett-Teller (BET) studies. TEM and SEM images showed that particles have spherical shapes and the average diameter size was about 50 nm. Formation of Mn3O4 compound was confirmed from FTIR studies. The XRD pattern showed that the Mn3O4 exhibit tetragonal hausmannite structure. The results of N2 adsorption-desorption analysis indicated that Mn3O4 nano–sphere has BET surface area of about 177.6 m2 g−1 and average pore diameters of 3 and 4 nm. The possible formation mechanism of Mn3O4 nanostructures has been discussed. The supercapacitive properties of Mn3O4 sample in 0.5 M Na2SO4 electrolyte showed maximum supercapacitance of 235.4 Fg−1 at scan rate 10 mV s−1. Coulumbic efficiency could be kept about 90% during 1000 cycles at 10 mV s−1. [Copyright &y& Elsevier]

Abstract: Manganese dioxide (MnO2) nanowires with diameter about 30–70 nm is achieved via a two-step process: first, template-free cathodic electrodeposition from aqueous solution of Mn(NO3)2 on steel substrate and followed by heat treatment. The temperature-annealed sample was studied by X-ray diffraction (XRD), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM) methods and Fourier transform infrared (FT-IR) spectroscopy. The electrochemical performance of the MnO2 sample was studied by cyclic voltammetry (CV) and chronopotentiometry in Na2SO4 solutions. The sample showed excellent supercapacitive behavior. The specific capacitance (SC) of 237 F g−1 in a potential window of 0–0.9V was obtained at the scan rate of 2 mV s−1. The SC calculated from the chronopotentiometry data is about 246 F g−1. The SC was decreased by 16% after 1000 cycles. [Copyright &y& Elsevier]

Manganese oxide nanostructures were synthesized by chemical–electrochemical process using controlled-current electrochemical methods and heat-treatment. Manganese hydroxide precursor was prepared by electrogeneration of hydroxide (OH − ) at electrode surface from nitrate solution. MnO 2 hexagonal nanostructures were then achieved by heat annealing of the obtained precursor. A variety of characterization methods have been applied to the samples including Fourier transform infrared spectrometry, energy dispersive X-ray analysis, X-ray diffraction and scanning electron microscopy. The scanning electron micrographs showed that the product consists of nanosized disc-like structures with average diameter of 800 nm and thickness of 50 nm. The electrochemical properties of MnO 2 nanostructures were investigated by Cyclic Voltammetry. The maximum specific capacitance achieved was 204 F g −1 at a scan rate of 1 mV s −1 . [ABSTRACT FROM AUTHOR]

A facile synthetic route has been proposed to prepare cauliflower-like nanostructures of Cr doped Mn 2 O 3 . The synthesis was carried out by constant current cathodic electrodeposition from Mn 2+ nitrate solutions containing minor amounts of dichromate. It was found that the presence of Cr mediates the formation of cathodic MnO 2 which then reacts with the excess Mn 2+ species to form Mn 2 O 3 nanostructures. X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Differential Thermal Analysis (DTA) were used to characterize the nanostructures. The storage ability of the obtained nanostructures was investigated by cyclic voltammetry (CV) in 0.5 M Na 2 SO 4 solution. The results indicated that the Cr doped manganese oxide material shows better performance than the non-doped one, and the charge capacity (SC) of doped manganese oxide (218 F/g) was higher than pure manganese oxide (208 F/g). [ABSTRACT FROM AUTHOR]