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Reversible Redox Transition and Pseudocapacitance of Molybdenum/Surface Molybdenum Oxides
Saji, Viswanathan S.,Lee, Chi-Woo The Electrochemical Society 2013 Journal of the Electrochemical Society Vol.160 No.1
<P>Redox transitions and superior pseudocapacitance are two typical characteristics in the electrochemical behavior of metallic Mo (with surface Mo oxides) and bulk Mo oxides; both of which were attributed to the participation of H<SUP>+</SUP>/cations. The effects of different electrolyte anions (Cl<SUP>−</SUP>, SO<SUB>4</SUB><SUP>2−</SUP> and ClO<SUB>4</SUB><SUP>−</SUP>) on redox transition and pseudocapacitance of thin-film ‘Mo/Mo oxides’ electrodes were assessed in this work through DC and AC electrochemical experiments. Voltammetric peak potentials and currents and potential-dependent pseudocapacitance were strongly dependent on the electrolyte's anion. The variations were tested at different electrolyte pH levels and using different electrolyte cations (Li<SUP>+</SUP>, Na<SUP>+</SUP> and K<SUP>+</SUP>). The results were correlated with those obtained using a Se<SUP>4+</SUP> based electrolyte. The findings reported here are expected to aid the applicability of Mo and its oxides in electrocatalysis, electrodeposition, supercapacitor, display, corrosion control and solar cells.</P>
Saji, Viswanathan S,Jo, Yimhyun,Moon, Hoi Ri,Jun, Yongseok,Song, Hyun-Kon Springer 2011 Nanoscale research letters Vol.6 No.1
<P>There are many practical difficulties in direct adsorption of polymers onto nanocrystalline inorganic oxide surface such as Al<SUB>2</SUB>O<SUB>3 </SUB>and TiO<SUB>2 </SUB>mainly due to the insolubility of polymers in solvents or polymer agglomeration during adsorption process. As an alternative approach to the direct polymer adsorption, we propose surface-bound polymerization of pre-adsorbed monomers. 6-(3-Thienyl)hexanoic acid (THA) was used as a monomer for poly[3-(5-carboxypentyl)thiophene-2,5-diyl] (PTHA). PTHA-coated nanocrystalline TiO<SUB>2</SUB>/FTO glass electrodes were prepared by immersing THA-adsorbed electrodes in FeCl<SUB>3 </SUB>oxidant solution. Characterization by ultraviolet/visible/infrared spectroscopy and thermal analysis showed that the monolayer of regiorandom-structured PTHA was successfully formed from intermolecular bonding between neighbored THA surface-bound to TiO<SUB>2</SUB>. The anchoring functional groups (-COOH) of the surface-crawling PTHA were completely utilized for strong bonding to the surface of TiO<SUB>2</SUB>.</P>
Saji, Viswanathan S.,Kim, Young-Soo,Kim, Tae-Hee,Cho, Jaephil,Song, Hyun-Kon Royal Society of Chemistry 2011 Physical chemistry chemical physics Vol.13 No.43
<P>Nanostructured materials have attracted recent research interest as battery materials due to their expected enhancement of properties. The characteristic nanoscale dimension and its structuring guarantees improved charge and mass transfer during charge/discharge processes. Among the potential cathode materials investigated as a substitute to LiCoO<SUB>2</SUB>, one of the most promising materials is LiFePO<SUB>4</SUB> with olivine structure (LFP). In this perspective article, the current research and development in the synthesis and electrochemical studies of nanostructured LFP are reviewed with a special emphasis on one-dimensional (1D) nanostructures and nanocompositing with 1D conductive materials. In addition to various examples of 1D LFP with detailed synthetic methods, why 1D nanostructures could be meaningful is discussed in terms of a geometric point of view and the anisotropic lithiation/de-lithiation mechanism of LFP.</P> <P>Graphic Abstract</P><P>One dimensionality (1D) as the first choice: (1) anisotropic feature of lithiation/delithiation in LiFePO<SUB>4</SUB> and (2) high aspect ratio guaranteeing large surface area make nanorods or nanotubes favored as the nanostructure of LiFePO<SUB>4</SUB>. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c1cp22818h'> </P>