M.V. Sangaranarayanan

The design of electrochemical supercapacitors exploiting the concept of underpotential deposition (UPD) is demonstrated using the UPD of thallium on silver as an illustrative example. The specific capacitance is deduced as 3.45×102 Farads g-1 from cyclic voltammetric studies employing the roughness factor for calculating the electroactive surface area.

The specific capacitance of polyaniline (PANI) deposited potentiodynamically on a stainless steel (SS) substrate, in the presence of p-toluene sulphonic acid (PTS) is estimated. Cyclic voltammetric experiments, galvanostatic charge-discharge studies and impedance analysis are carried out in order to investigate the applicability of the system as an electrochemical supercapacitor. Fourier transform infrared (FTIR), X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques are employed for characterization of the electrode. © 2006 Elsevier B.V. All rights reserved.

An explicit expression for the exchange current density in terms of work function of the metal surface, surface potential of the reactants and products, and solvation energies was derived. The usefulness of the expression was demonstrated for a ferric/ferrous reaction whose i0 values have been reported for a variety of electrodes using experimental data and theoretical calculations.

A new parametric relation for hardness incorporating the surface potential of the metal and work function was derived. Hydrogen evolution and ferric/ferrous redox reactions were considered as examples to extract chemical hardness from electrode kinetic data.

A systematic way of distinguishing stepwise and concerted mechanisms in reductive cleavage reactions has been formulated involving current function analysis of the voltammetric data. The electrochemical reductive cleavage of the carbon-iodine bond in 1,3-dichloro-2-iodobenzene has been analyzed from a mechanistic point of view to illustrate the methodology. 1,3-Dichloro-2- iodobenzene undergoes an initial stepwise electron transfer obeying quadratic activation-driving force relationship. The current function analysis yields the reorganization energy for the reduction of 1,3-dichloro-2-iodobenzene and the results have been verified independently using convolution potential sweep voltammetry. © 2004 Elsevier Ltd. All rights reserved.

A novel method of deducing the parameters of electron density profiles pertaining to the theoretical re-construction of X-ray reflectivity data of liquid metals is proposed and the inter-dependence of various parameters of the electron density is indicated. The crucial role played by the diffusion coefficient, viscosity and critical temperature of the metals in dictating the correlation lengths is pointed out. The applicability of the methodology is demonstrated for the experimental data on the X-ray reflectivity of Ga, In and K. © 2009 Elsevier B.V. All rights reserved.

A lattice gas model formalism under mean field approximation is developed for the analysis of differential capacitance pertaining to liquid/liquid interfaces. The interfacial profiles for the two solvent mole fractions are chosen and ionic charge densities are estimated by minimizing the Helmholtz free energy. The dependence of the differential capacitance on various interaction energies, electrolyte concentrations and dielectric constants is indicated. The influence of the solvent density profile is analyzed and deviations from the predictions of Gouy-Chapman theory are pointed out.

The hydration energies of C60 and C70 are estimated at temperatures ranging from 20 to 90 °C by incorporating the cavity formation energies and van der Waals contributions. The structural parameters of the fullerenes are deduced using the optimized geometries from Gaussian 03 version while those pertaining to water are obtained from the TIP4P model. The cut-off radii pertaining to the sphere of influence of fullerenes with water are incorporated using a simple Monte Carlo simulation methodology and the entropy changes involved in the hydration are also evaluated. © 2006 Elsevier B.V. All rights reserved.

The estimation of electrochemical quartz crystal microbalance (EQCM) frequencies from a given cyclic voltammetric data is analysed using underpotential deposition (UPD) of metals as an illustrative process. The crucial role played by the surface roughness of electrodes and electrosorption valency of the depositing species is pointed out. The computed EQCM frequency shifts for the UPD of Cd and Tl on polycrystalline Ag electrodes are in satisfactory agreement with the experimental data. © Springer-Verlag 2005.

Onsager's formalism of nonequilibrium Thermodynamics is employed to analyze competitive diffusion processes pertaining to charge transport through redox polymer electrodes. The validity of reciprocity relations is demonstrated for electron hopping in the case of [Ru(NH3)6]3+/2+ couple on Nafion coated Glassy Carbon (GC) electrodes. The phenomenological coefficients pertaining to electron hopping and physical diffusion are estimated using the experimental data of Cp2FeTMA2+/l+ on Nafion coated GC electrodes. The redox conductivity and transport numbers are expressed in terms of Onsager's coefficients and the calculation of the phenomenological coefficients directly from the charge propagation behavior is demonstrated. The expression for entropy production is shown to yield new insights regarding the interpretation of diffusion coefficients in redox polymeric systems. © 2001 American Chemical Society.