Graphene, a single atom thick carbon material with high surface area and electrical conductivity provides an ideal platform for designing high performance electrochemical devices. This paper reports the synthesis of phosphorous doped graphene from reduced graphene sheets, its characterization by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy and its use for supercapacitor applications. The specific capacitance was found to be 367 Fg(-1) from electrochemical measurements. These samples show a high power density of 9 kW kg(-1) and energy density of 59 Wh kg(-1) in an aqueous electrolyte solution, which is much higher than other graphene-based supercapacitors. The phosphorus-doped graphene showed a high potential for use in low cost energy storage devices.

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A low-cost polyester cellulose paper has been used as a substrate for a flexible supercapacitor device that contains aqueous carbon nanotube ink as the electrodes and a polyvinyl alcohol (PVA)-based gel as the electrolyte. Gel electrolytes have attracted much interest due to their solvent-holding capacity and good film-forming capability. The electrodes are characterized for their conductivity and morphology. Because of its high conductivity, the conductive paper is studied in supercapacitor applications as active electrodes and as separators after coating with polyvinylidene fluoride. Carbon nanotubes deposited on porous paper are more accessible to ions in the electrolyte than those on flat substrates, which results in higher power density. A simple fabrication process is achieved and paper supercapacitors are tested for their performance in both aqueous and PVA gel electrolytes by using galvanostatic and cyclic voltammetry methods. A high specific capacitance of 270 F g(-1) and an energy density value of 37 W h kg(-1) are achieved for devices with PVA gel electrolytes. Furthermore, this device can maintain excellent specific capacitance even under high currents. This is also confirmed by another counter experiment with aqueous sulfuric acid as the electrolyte. The cycle life, one of the most critical parameters in supercapacitor operations, is found to be excellent (6000 cycles) and less than 0.5 % capacitance loss is observed. Moreover, the supercapacitor device is flexible and even after twisting does not show any cracks or evidence of breakage, and shows almost the same specific capacitance of 267 F g(-1) and energy density of 37 W h kg(-1) . This work suggests that a paper substrate can be a highly scalable and low-cost solution for high-performance supercapacitors.

Team work: Mesoporous Pt-Ru alloy particles with uniform sizes are synthesized by controlled chemical reduction with ascorbic acid using mesoporous silica as a hard template. Elemental mapping shows uniform distribution of Pt and Ru particles. The electrochemical activity and stability of the alloys towards methanol oxidation much higher than that of mesoporous Pt and commercial Pt catalyst.