Preparation Of Free-standing TiO₂Hollow Microspheres Array And Its Photoelectrochemical Performance Research

TiO2has become a very promising photocatalyst attracted much attention in the last few years, for its nontoxic, cheap, good chemical stability, higher photocatalytic activity In recent years, the design and improved of the TiO2structure had attracted more and more attention. T1O2hollow microspheres structure is becoming a hot research topic in the zero-dimensional nanomaterials. TiO2hollow microspheres structure not only have a larger specific surface area, but also have some unique properties by the hollow structure, such as low density, high surface high surface permeability and so on. The preparation of TiO2hollow microspheres is complex and the hollow microspheres are easily damaged by multiple factors in the process of the preparation. That’s the reason of the production rate of the TiO2hollow microspheres is too low. In the process of application, the suspended microsphere is easy to reunite, not easy to separation and difficult to recycle, these problems seriously restrict the application of TiO2hollow microspheres.For the above problems, in this study we ultilized colloid interfacial self-assembly method to prepare highly ordered monolayer polystyrene (PS) microspheres template on the Ti substrate for directly deposition anatase TiO2membrance on the template by liquid phase deposition method. Finally the PS microspheres were removed by calcination. This preparation technology has two advantages:(1) highly ordered template on pure titanium substrate were prepared by Colloid interfacial self-assembly. It is not necessary to centrifugal separation the microspheres in the process after the template immobilized to the substrate that would optimize process;(2) Liquid phase deposition method can get the TiO2anatase phase directly. It is a good way to get a complete hollow microspheres by avoid the high temperature damaged the microsphere structure. In this study the highest calcination temperature is only350℃The morphology structure of the TiO2hollow microspheres arrays were characterized by SEM, FTIR and XRD methods.The result shows that the obtained TiO2hollow microspheres array structure is complete, highly ordered, it is hollow structure. The diameter of microspheres is2μm and the shell was anatase TiO2membrance.The thickness of the shell is35nm.The photoelectrochemical performance of TiO2hollow microspheres array was test by transient current, open circuit potential, linear sweep voltammetry, and electrochemical impedance spectrum. The results showed that the preparation of TiO2hollow microspheres array has a good photoelectric response performance. In the absence of applied bias, the photocurrent can reach0.25mA/cm2, open circuit potential was0.7V, the photoelectric conversion efficiency was0.25%. These properties are higher than the TiO2membrance by the same liquid deposition method. These results suggested that thehollow structure spheres have more advantageous in the photoelectric conversion. Combining with Nyquist diagram and the semiconductor/solution interface theory we fitted out a reasonable equivalent circuit model and analysis of the electrode process by this model.TiO2hollow microspheres arrays was test by the PL spectrum, a photoluminescence peak was existe at372nm.This peak was come from anatase TiO2band gap transition and recombination. Compared with TiO2membrance, the response spectrum was extended, the emergence of new emission peak at472nm, this is attribute to nanomembrance preparation by sacrifice template of liquid phase deposition method that form a new surface state. Surface states expanded the TiO2hollow microspheres response spectrum. The shell of the microspheres and the TiO2membrance are the same crystalline phases, so we can suggested that the new peak comes from the different of the structure. The result shows that the hollow microspheres structure is good for the light absorption.In this paper, on the basis of zero dimensional TiO2hollow microspheres we used a simple method to preparation of one-dimensional TiO2nanotubes and characterization.The results further prove the hollow low-dimensional nanomaterials have better photoelectric properties.