Preparation And Electrochemical Property Studies Of Three Dimensional Electrodes

Direct ethanol fuel cell (DEFC) and electrochemical capacitor (EC) are two kinds of important energy storage/conversion devices that are being widely studied at present. On account of large energy conversion efficiency and green environmental conservation, DEFC has attracted extensive attention of the world. EC has already become one of the research interests related to new chemical energy sources studies because of its higher power density and longer cycle life than secondary batteries and its higher energy density compared to conventional electrical double-layer capacitors. Generally, the performance, cost and cycle life of DEFC and EC are restricted by the electro-active materials and the structure of the electrode.In this thesis, we have reviewed the newest development in the research of electrode materials of both DEFC and EC devices, optimized and modified the electrode structure. The main results are as follows:1. A 3D hierarchically structured Pd electrode has been successfully fabricated by directly electrodepositing Pd nanoparticles on the Ni foam. The well-dispersion and hierarchical structures of Pd nanoparticles on the Ni foam provide a much larger surface area for reaction, leading to the effective utilization of the electrode material. The Pd/Ni foam electrode displays improved electro-catalytic activity and stability for ethanol oxidation. As a result, the Pd/Ni foam electrode with superb performance, relatively low cost as well as simple fabrication procedure is a promising candidate for the conventional carbon supported electrode for the wide applications in DEFCs.2. The 3D MnO2 and 2D MnO2 film electrodes were fabricated by direct electrochemical deposition method. The electrochemical results showed that the 3D MnO2 electrode has higher specific capacitance, better rate capability and lower resistance than 2D MnO2 film electrode. Therefore, MnO2/Ni foam electrode is a promising electrode for electrochemical capacitor.3. Based on the previous study, Pd nanoparticles were firstly deposited on the surface of the Ni foam to modify its property and then fabricate MnO2/Pd/Ni foam electrode by electrochemical deposition. The electrochemical studies show that the MnO2/Pd/Ni foam electrode possesses higher Cs, lower resistance and more excellent rate performance than MnO2/Ni foam electrode. Moreover, the introduction of Pd nanoparticles is beneficial for the improvement of the cycling performance.4. Free-standing Ti nanowires were prepared by a low-cost, reproducible, one-step hydrothermal method. We investigated the effect of time and volumn of the HCl solution on the morphology of the Ti nanowires. Large-scale nanowires with a wide range of diameters were formed on the Ti substrate when the reaction time is 8 h. Increasing the reaction time to 10 h, the Ti substrate is well covered by highly dense and uniform nanowires with diameters of 30～40 nm.