Preparation and performance of functional materials for catalyst and energy applications

Abstract

The main aim of this dissertation is to study the preparation and performance of functional materials, including coconut shell based activated carbon (ACCS), coconut shell based activated carbon-titania hybrid (ACCS/TiO2), and titania-based ceramics/polymer hybrid materials for energy storage and photocatalyst applications. Coconut shell was successfully utilized as a low cost alternative material for the electrode in supercapacitor device and the removal of textile dye. The highly porous activated carbon with high specific surface area was prepared from agricultural coconut shell waste as precursor with KOH activation at impregnation ratio of 3:1 and carbonization at 800 °C. For electrochemical test, the obtained ACCS electrode showed excellent electrochemical behavior with a maximum specific capacitance of 149.65 F/g at a current density of 0.5 A/g and the highest energy density of 4.64 Wh/kg at the power density of 239.66 W/kg. Furthermore, this resulting electrode also showed good rate capability and the specific capacitance decreased less than 35% (65% capacity retention) as the current density was raised from 0.5 to 4 A/g. For photocatalytic test, TiO2/activated carbon double-layered film photocatalyts were successfully fabricated using an electrophoretic deposition technique without additives. Pristine TiO2 powder was synthesized by solvothermal process. The obtained hybrid catalyst film showed the maximum efficiency for removing methylene blue of about 97% at 60 min under UV light.The hybrid film system has an advantage for wastewater treatment in practical applications because it is easy to separate from the process and reusable with relatively high photocatalytic efficiency. Furthermore, the titania-based ceramics-polymer hybrid materials; bismuth titanate/polyvinylpyrrolidone (BiT/PVP) and barium titanate/poly-(vinylidene fluoride) (BTNFs/PVDF) nanohybrids, were prepared and their performances were tested. The nanohybrids were synthesized and fabricated using the sol-gel chemistry followed by extrusion based 3D-printing (FDM) technique. The BiT/PVP sample with 3.0 vol. % of PVP exhibited a good printing speed range enlarged over 50% of pure BiT gel. The obtained results are useful for optimizing and setting the 3D printing parameters. Moreover, the anisotropic 3D BTNFs/PVDF nanohybrids were successfully fabricated via FDM technique and BTNFs were synthesized via sol-gel followed by electrospinning method. The BTNFs/PVDF 3D-nanohybrids with 20 vol. % BTNFs, exhibited the highest dielectric constant in cross-direction around 200 at frequency of 1 kHz at room temperature, vs 13 of the neat PVDF materials. This FDM technique indicated great potential for future development in high-k ferroelectric ceramic/polymer composites with controllable anisotropic properties.

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