Tungsten oxide/Carbon Aerogel Composite for Applications in Supercapacitors

• Main Authors: Wang, Yong-Huei, 王詠慧
• Other Authors: Lu, Shih-Yuan
• Format: Others
• Language: en_US
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/49916452351874950607

碩士 === 國立清華大學 === 化學工程學系 === 100 === Tungsten trioxide, a low cost and an environmentally friendly supercapacitive material, is deposited as a thin nanostructure of nanocrystals into carbon aerogels, a mesoporous host template of high specific surface areas and high electric conductivities, with a wet chemistry process. This tungsten trioxide/carbon aerogel composite shows ultrahigh specific capacitances(tungsten trioxide based) of around 700 F/g at a scan rate of 25 mV/s within a potential window of -0.3 to 0.5 V in 0.5M H2SO4 solutions. The composite also possesses an excellent high rate capability manifested by maintaining specific capacitances above 480 F/g at a high scan rate of 500 mV/s, and an outstanding cycling stability demonstrated by a negligible 5% decay in specific capacitances after 4000 cycles. The success is attributable to the fuller utilization of tungsten trioxide for supercapacitance generation, made possible by the composite structure enabling largely and well exposed tungsten trioxide to the electrolyte and easy transport of charge carriers, ions and electrons, within the composite electrode. Plain tungsten trioxide electrodes are also investigated. The as-prepared tungsten trioxide nanoparticles are synthesized with a sol-gel process, followed by calcination at 400 oC. The specific capacitances of plain tungsten trioxide electrodes are 53.7F/g at a scan rate of 25mV/s within a potential window of -0.3 to 0.5 V in 0.5M H2SO4 solutions. When the scan rate is increased to 500mV/s, the specific capacitances of the plain tungsten trioxide electrode decrease by 60%. Symmetric capacitors composed of two tungsten trioxide/carbon aerogel composite electrodes are studied. The specific energy and specific power of this device equal 2Wh/kg and 6.2kW/kg, respectively. The products have been characterized with X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM),X-ray spectroscopy (XPS), wide angle X-ray scattering (WAXS), surface area and pore size analyses (BET), and cyclic voltammetry (CV).