Preparation And Photoelectric Properties Of Co-catalyst-loaded TiO₂Nanotube-Array

Due to the environmental crises and energy shortage issues, clean and renewable energy that will replace fossil fuels is imminently for human society. Solar water splitting has been one of the most attractive strategies to address the energy shortage issues and environmental crises since Honda and Fujishima demonstrated water splitting with TiO2in1970s. TiO2nanotube arrays (TNTAs) present extraordinary photoelectro-chemical catalysis properties due to their unique vertical aligned geometric structure. However, the solar water splitting efficiency of pure TNTAs is still low. Building a composite photocatalytic system is the inevitable road to realize efficient water splitting. In this thesis, we attempt to build a highly efficient and stable water splitting hydrogen production system by modify the TNTAs through coating with appropriate co-catalyst.TNTAs photoanode was fabricated in deionize water and ethylene glycol mixed electrolyte containing a certain amount of NH4F by electrochemical anodization. Then, the Pt/TNTAs composite photoanode was prepared through coating Pt nanopatricles on the surface of TNTAs use a mothed of photo reduction. The photoanode was characterized by UV-vis absorption spectra(UV-vis), X-ray diffraction(XRD), X-ray photoelectron spectroscopy(XPS), scanning electron microscope(SEM) and transmission electron microscopy(TEM), respectively. The photoelectrochemical activities were also measured. It was found that the Pt/TNTAs composite electrodes showed much higher rate of photocatalytic hydrogen generation compared to pure TNTAs electrodes. The reason is that the electrons generated in TNTAs can effectively transfer to Pt nanoparticles, facilitating the separation of the photogenerated carriers, and thus improving the photocatalytic hydrogen production efficiency.We also studied the photoelectrochemical properties of Co-Pi deposited TNTAs composite photoelectrodes. The Co-Pi nanoparticles were deposited on the surface of TNTAs through a mothed of photoelectrochemical reduction. The composite photoelectrodes were characterized by UV-vis, SEM and TEM. The photoelectrochemical activities were also tested using an electrochemical workstation. The results showed that the photoelectrochemical properties of the Co-Pi/TNTAs electrodes were greatly improved compared with pure TNTAs electrodes. This is mainly due to the Co-Pi nanoparticles can capture photogenerated holes and effectively reduce the overpotential of the redox reaction, then the photogenerated holes can effectively participate in water oxidation reaction, reduce the composition of the photogenetated electron-hole pairs.