Solar Hydrogen Generation Via Water Splitting On TiO₂Nanotube Arrays

Hydrogen production from water splitting on photocatalysts driven by solar energy is an environmental way for using renewable energy. In this thesis, the recent research progress on the key photocatalytic materials and technology is summarized. The development direction of photocatalytic technologies for hydrogen production from water splitting in the future is predicted. Enhancing the photocatalytic activity by controlling the nanoscale structures and designing hybrid devices is the importance development direction. Therefore, in order to seek technologies for improving efficiency, photocatalytic properties of TiO2nanotube arrays with the special structure were studied in our work.TiO2nanotube arrays (TNAs) were prepared by anodization. The relationship between the preparation conditions and photocatalytic hydrogen evolution properties on TNAs was discussed. Influences of anodization potentials, durations, steps and thermal treatment temperature on the electrode performance were identified by the orthogonal test. Photoelectrochemical properties of electrodes were tested by electrochemical work station. Combining means of SEM, XRD and UV-vis Diffuse reflectance spectra, the underlying mechanisms were analyzed. The results showed that TNAs prepared under different conditions of anodic oxidation and thermal treatment led to different microstructure and crystalline phase composition, and consequently affected the photocatalytic performance. Highly-ordered TNAs could be achieved after first-step anodization at60V for1h. Layered mixed crystal was obtained by thermal treatment at450℃. Furthermore, multiple photocatalytic experiments were conducted using the electrode in0.5M Na2SO4+0.5M ethylene glycol water solutions under UV light. The H2evolution rate could be up to about5.3mL/h-cm2at a0.5V bias. And the electrode showed good photocatalytic stability by repeated trials.Pt nanoparticles were assembled on the surface of TiO2nanotube arrays (Pt/TNAs/Pt) by photochemical reduction. Microstructure, element composition and optic-electronic properties of the electrodes were analyzed by means of SEM, EDS, UV-vis diffuse reflectance spectra and transient photocurrent response. A two-electrode photoelectrochemical cell was constructed to study the charge transfer property. The results show that photogenerated electrons can transfer to Pt nanoparticles and efficiently prompt hydrogen evolution. According to this mechanism, single side Pt-assembled TiO2composite electrode (Pt/TNAs) was designed and fabricated. The photocatalytic hydrogen generation reaction results showed that the photocatalytic activity of Pt/TNAs was close to Pt/TNAs/Pt. The H2evolution rate could be up to about1.2mL/h·cm2, and was6times higher than that of pure TiO2nanotube arrays.