Fabrication Of Metal Oxide Nanowires And Nanoflakes For Photoelectrochemical Application

With china's sustained and rapid economy development, the issule of energy shortage has now become greatly emergent, and thus to develop a environmentally benign, high efficient renewable energy is of great important for current research work. Since hydrogen is considered to be one of the representiative of clean energy, photoelectrochemical water splitting has attracted remarkable interests in recent decades. This dissertation focuses on developing visible light active metal oxide semiconductor with unique nanostructure and evaluating their photoelectrochemical perfomacne.α-Fe2O3 (Hematite) nanowire arrays, grown along [110]direction on FTO, Ti, W, Pt, was successfully fabricated through simple and quick solvothermal approach in ethanol and acetonitrile. The controlled growth of nanowire by adjusting parameters such as temperature, duration time and pH was investigated. The Sn and Ti doping were achieved by annealing wires grown on FTO and Ti foil, respectively, at high temperature. The effects of annealing rigime, temperature, seed layer and grain boundaries on impurity doping was discussed. Additionally, here reported for the first time that a-Fe2O3 nanowires were coated by SiO2 to avoid etching of hot flow of Ar. Photocurrent and IPCE was significantly improved after doping. Flat band potential and donor density were calculated by Mott-Schottcky analysis and their effects on photocurrent were also discussed. The feasibility of conversion of nanowire to nanotube was analysized, the results show that it is possible but further research is still need to optimize the conversion condition.The second section of the dissertation focuses on ultrathin nanosheet assembled multilayer film by hydrothermal treatment of W foil at low temperature (80℃). The parameters influential to the film growth and morphology was discussed. XRD suggests the WO3 H2O phase of as-prepared samples, which can then be converted to WO3 by annealing. Some interesting changes in morphology were observed after annealing that ultrathin nanosheet combined to form thicker one and mesoporous morphology was found for 500℃annealed 17 h sample. The relatively low bias (0.55 V vs Ag/AgCl) at saturation photocurrent for all the samples tested is due to the existence of underlying compact layer, which might be able to protect electrons at W substrate from reacting with photo-generated oxygen, thus dark curret was therefore limited.4μm thick film is required for WO3 to absorb enough photons and obtain high photocurrent. IPCE of 40% at 400 nm imply the WO3 with the unique morphology discussed above is an interesting material for photoelectrochemistry and other electrochemical applications.