Electrochemical Performances And Preparation Of Mesoporous TiO₂ Nanotube Arrays

TiO2 nanotube arrays (TiO2 NTAs) are widely applied in biosensor, photoelectrochemical sensor and solar cell, due to the special physical and chemical properties, ordered nanostructure and good adhesion to the substrate. In this study main efforts were focused on the construction of mesoporous TiO2 NTAs and their electrochemical properties. The main works carried out are listed as following:1. Novel mesoporous TiO2 NTAs are synthesized with anodization method combined with chemical etching using different concentration of HF solution, and used for glucose biosensor. The immobilization of glucose oxidase (GOx) as enzyme model onto the mesoporous TiO2 NTAs electrodes provide an efficient biosensor for amperometic detection of glucose. The morphology, structure, component and electrochemical property of mesoporous TiO2 NTAs are characterized by scanning electron microscope, high resolution transmission electron microscope, X-ray diffractometer, X-ray photoelectron spectrometer and electrochemical workstation. The mechanism of mesoporous structure on promoting electrochemical performance are discussed in detail by comparing the cyclic voltammograms of TiO2 NTAs and mesoporous TiO2 NTAs etched in different conditions. The amperometric response of glucose on GOx/TiO2-0.5NTAs electrode is linearly proportion to glucose concentration in a range from0.1 to 6 mM with a sensitivity of 0.92 μA·cm-2·mM-1.2. Novel mesoporous TiO2 NTAs were synthesized by anodization method combined with chemical etching in HF solution of different hydrothermal temperatures for enhancing the photoelectrochemical activity. Morphologies, structures and elemental compositions of mesoporous TiO2 NTAs were characterized with scan electron microscope, high resolution transmission electron microscope, X-ray diffractometer and X-ray photoelectron spectrometer. Higher photoelectrochemical activities of mesoporous TiO2 NTAs can be achieved with the highest photocurrent triple that of un-etched TiO2 NTAs. High electrochemical active surface area, optical absorption ability and charge transfer rate play key roles on enhancing the photoelectrochemical activity of mesoporous TiO2 NTAs.3. Anatase TiO2 NTAs were hydrothermally treated in Na2S solution, and the photoelectrochemical performances were systematically studied. Morphology, structure, elemental component and photoelectrochemical performances of treated TiO2 NTAs were characterized by scanning electron microscope, high resolution transmission electron microscope, X-ray diffractometer, X-ray photoelectron spectrometer and electrochemical workstation, respectively. The influence of the sulfide treatment on the photoelectrochemical performance is discussed in detail by measuring cyclic voltammogram, chornoamperogram and chemical impedance spectrum of treated TiO2 NTAs in different conditions. TiO2 NTAs sulfide treated in 30 mM Na2S solution at 135℃ possess the highest photocurrent of 289 nA, which is 3.3 times that of untreated TiO2 NTAs. High optical absorption, electrochemical active surface area and electron transfer rate due to the mesoporous structure rather than sulfide dropping play key roles in enhancing the photoelectrochemical activity of the TiO2 NTAs.4. Homogeneous nano-crystalline modified TiO2 NTAs were synthesized by anodization method combined with hydrothermal method in HF solution. Morphology, structure, elemental component and photoelectrochemical performances of homogeneous nano-crystalline modified TiO2 were characterized by scanning electron microscope, X-ray diffractometer, X-ray photoelectron spectrometer and electrochemical workstation, respectively. The influence of homogeneous TiO2 modified TiO2 NTAs on the photoelectrochemical performance is discussed in detail by measuring cyclic voltammogram, chornoamperogram and chemical impedance spectrum of treated TiO2 NTAs in different conditions. The results showed that TiO2 NTAs with the immersion time of 30 min, hydrothermal time of 6 h possess the highest photocurrent of 370.1 μA. The mechanisms of homogeneous nano-crystalline TiO2 NTAs modifications were studied through the whole electrochemical process, including light absorption, charge transport process and surface electrochemical reaction. The results showed a stronger light absorption, high charge mobility and large electrochemical activity area result in producing high photoelectric fundamental chemical activity lies.