T.K. Tan

A REVIEW OF METAL OXIDE COMPOSITE ELECTRODE MATERIALS FOR ELECTROCHEMICAL CAPACITORS

With the emerging technology in the 21st century, which requires higher electrochemical performances, metal oxide composite electrodes in particular offer complementary properties of individual materials via the incorporation of both physical and chemical charge storage mechanism together in a single electrode. Numerous works reviewed herein have identified a wide variety of attractive metal oxide-based composite electrode material for symmetric and asymmetric electrochemical capacitors. The focus of the review is the detailed literature data and discussion regarding the electrochemical performance of various metal oxide composite electrodes fabricated from different configurations including binary and ternary composites. Additionally, projection of future development in hybrid capacitor coupling lithium metal oxides and carbonaceous materials are found to obtain significantly higher energy storage than currently available commercial electrochemical capacitors. This review describes the novel concept of l...

LiFePO4 - Activated Carbon Composite Electrode as Symmetrical Electrochemical Capacitor in Mild Aqueous Electrolyte

In this study, a symmetric electrochemical capacitor has been fabricated by adopting the lithiated compound (LiFePO4)-activated carbon (AC) composite as the core electrode materials. The electrochemical performances of the prepared supercapacitor were studied using cyclic voltammetry (CV) in 1.0 M Na2SO3 solution. Experimental results reveal that the maximum specific capacitance of 112.41 F/g is obtained in 40 wt % LiFePO4 loading on AC electrode in comparison to that of pure AC electrode (76.24 F/g) in 1 M Na2SO3. The enhanced capacitive performance of the 40 wt % LiFeO4 –AC composite electrode is believed attributed to the contribution of synergistic effect of electric double layer capacitance (EDLC) on the surface of AC as well as pseudocapacitance via intercalation/extraction of Na+, SO32-and Li+ ions in LiFePO4 lattices. The composite electrodes can sustain a stable capacitive performance at least 1000 cycles with only ~5 % specific capacitance loss after 1000 cycles. Based on the findings above, 40 wt % LiFeO4 –AC composite electrodes which utilise low cost materials and environmental friendly electrolyte is worth being investigated in more details.

The Photodegradation of Organic Compounds by ZnO Nanopowder

The commercialized ZnO nanopowder has been employed in this study to investigate the photocatalytic degradation of two organic compounds, Methylene Blue (MB) and Phenol Red (PR) in an aqueous suspension of ZnO nanoparticles under UV light irradiation. This study has considered ZnO as the photocatalyst because it has been reported as a suitable substitute for TiO2 in certain application. For the characterization of the ZnO photocatalyst, X-ray diffraction (XRD), transmission electron microscopy (TEM), specific surface area analysis (BET), and UV-visible spectroscopy were exploited. X-ray diffractometry result for the ZnO nanoparticles exhibit normal crystalline phase features. All observed peaks can be indexed to the pure hexagonal wurtzite crystal structures, with the space group of P63mc. From the XRD pattern, no diffraction peaks from other impurities have been observed. In addition, TEM measurement shows that most of the nanoparticles are spherical and rod-like in shape and fairly monodispersed. A significant degradation of the organic compounds were observed in the presence of the catalyst without the irradiation of the UV light and the degradation increases significantly when irradiated with the UV light for a certain period of time. Besides, for the same period of irradiation, the photodegradation of the organic compounds was increased as the photocatalyst loading increases. The BET measurement for ZnO was 11.9 m2/g. The effect of some parameters such as initial concentration of organic compounds and photocatalyst loading were also determined. Keywords: Nanostructures; Methylene blue; Phenol red; Zinc oxide; Heterogeneous photocatalyst