| Environmental pollution and energy shortages are the two major global problems and also the most severe challenges for our human beings to be solved in the 21st century. Energy harvested directly from sunlight offers a desirable approach toward green and sustainable energy system. However, low-cost, high efficiency and long operation life are required for practical applications for the global demand, but they are very challenging. Currently the photovoltaic, photothermal, solar water splitting and organic pollutants degradation by utilizing solar energy are promising research field. As we all known, the performance of energy systems strongly depends on the physicochemical properties and structures of electrode materials. Nowadays, more and more nanomaterials with special functions have been developed for high efficient energy conversion systems including solar cells. In particular, functionalizations of electrode materials in nanoscales to tailor the chemical composition and physical structure could be a very important approach to achieve high efficient solar energy systems. Comparing to other semiconductor photocatalyst, TiO2 has many advantages, such as richness, high photocatalytic activity, innocuousness and stability. TiO2 semiconductor photocatalyst has become the most promising candidature in the field of environmental purification and new energy generation. Recently, TiO2 has been studied extensively in the photocatalytic field. However, it has still not been applied in practice because of two reasons:fast recombination of the charge carriers and no light absorption in the visible region due to its large band-gap (e.g.,-3.2 eV for anatase), thus cannot fully utilize solar energy.In this dissertation, I mainly focus on the modified TiO2 nanorod arrays by doping and composing semiconducting materials and investigations of their photoelectrocatalytic behaviors. Moreover, the mechanisms to enhance the photoelectrocatalysis are discussed to explore the scientific insights. The details are summarized briefly as follows:Firstly, largely voided TiO2 nanorod arrays were synthesized and further modified with a thin layer of α-Fe2O3 (Fe2O3@TiO2) by pyrolysis of FeCl3 ethanol solution as a photoanode toward water oxidation, showing significantly improved photoelectrochemical performance over TiO2 nanorod array. The optimal nonorod array photoanode delivers the highest photocurrent density of 3.39 mA/cm2 at 1.23 V (vs RHE) and achieves a greatly improved applied bias photon-to-current efficiency (ABPE) (1.153%) under 100 mW/cm2 UV-vis light illumination, which is-3.3 times higher than that of TiO2 nonorod array electrode and is also remarkably better than the reported Fe2O3-decorated randomly arranged TiO2 nanorods photoanode (Fe2O3@TiO2 RNRs) and densely arranged TiO2 nanotube by～11.3 times and ～6.2 times respectively. The great enhancement is mainly originated from a thin layer of Fe2O3 modification on largely voided TiO2 nanorods array, which improves the absorption of UV light, boosts the charge interface transfer rate, reduces the charge diffusion length and suppresses the charge recombination process. This work could provide a feasible route to improve the photoelectrochemical catalytic performance of TiO2 semiconductor toward water splitting.Secondly, the TiO2 nanorod arrays were doped with Sn. We found that doping didn’t change the morphology of TiO2 nanorods by a series of characterizations such as XRD, UV-vis, FESEM and TEM. The PEC performance indicated that Sn doping can improve the visible-light absorption and raise the photocatalytic activity of TiO2 nanorods.The works performed in the thesis reveal that doping and composition can be used to synthesis TiO2 based-photoelectrode that can significantly improve the kinetic and thermodynamic limits to result in efficient photoelectrical catatalysis for high performance devices. |
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