Vinay V. Bhat

Thermal Treatment Effects on Charge Storage Performance of Graphene-Based Materials for Supercapacitors

Graphene materials were synthesized by reduction of exfoliated graphite oxide and then thermally treated in nitrogen to improve the surface area and their electrochemical performance as electrical double-layer capacitor electrodes. The structural and surface properties of the prepared reduced graphite oxide (RGO) were investigated using atomic force microscopy, scanning electron microscopy, Raman spectra, X-ray diffraction pattern analysis, and nitrogen adsorption/desorption studies. RGO forms a continuous network of crumpled sheets, which consist of large amounts of few-layer and single-layer graphenes. Electrochemical studies were conducted by cyclic voltammetry, impedance spectroscopy, and galvanostatic charge-discharge measurements. The modified RGO materials showed enhanced electrochemical performance, with maximum specific capacitance of 96 F/g, energy density of 12.8 Wh/kg, and power density of 160 kW/kg. These results demonstrate that thermal treatment of RGO at selected conditions is a convenient and efficient method for improving its specific capacitance, energy, and power density.

Effect of carbon addition on hydrogen storage performances of magnesium-based alloys: From bulk powders to thin films

Mg-based thin films were successfully grown by Pulsed Laser Deposition. Dramatic optical changes were observed depending on the conditions of deposition. Films grown in vacuum were shiny metallic whereas the ones grown in a Ar/H 2 gas mixture were highly transparent. Ex situ hydrogenation, by annealing the films at 200 °C in 15 bars of hydrogen, led to similar metallictransparent transformation. Mg-C x (x ≤ 20 %) films show a faster hydrogenation associated with a significant decrease in oxygen content by carbon addition.