Researches On PEC Properties And Performance Of Hydrogen Production Via Photocatalytic Water Splitting Of Materials Based On 1D TiO₂ Nanotube/nanorod Arrays

Increased demand for energy is driving increased consumption of fossil fuels.While fossil fuels are readily available and relatively inexpensive,their combustion results in the emission of greenhouse gases,which linked to global climate change.Thus,research efforts towards a fundamental understanding and application of conversion systems for renewable energy sources such as solar,wind,geothermal and tidal power have been dramatically increased.In 1972,using a semiconducting Ti02 electrode,Fujishima and Honda reported the Honda-Fujishima effect,or the photo-oxidation of water using ultraviolet radiation from the sun,forming hydrogen fuel along with oxygen.Since the publication of Fujishima's work,there has been a sustained effort to identify and engineer new materials for more efficient photoelectrochemical(PEC)cell systems.However,the main challenge to the widespread implementation of PECs is the poor conversion efficiency of photoanode materials currently being used in these devices.Therefore the motivation for our research is to develop PECs can be easily constructed from inexpensive materials,making them an economical alternative to traditional photovoltaic solar harvesting systems.The overall research work of this thesis is composed of four fractions:(1)TiO2 nanotube arrays(TNAs)were prepared on a metal titanium substrate by anodic oxidation,and the rGO modified TNAs samples were further obtained by one-step reduction method by using graphene oxide(GO).The experimental results show that the graphene layer can modify the surface defects of the nanotube effectively.Under the appropriate proportion of graphene modification,both the expansion of the light absorption and the increases of photo-induced carreier concentration greatly improved the photocatalytic reaction activity at the surface of the photoelctrode as we prepared.(2)The growth mechanism of single crystal Ti02 nanorod arrays(TNRs)was systematically studied by using the rigid transparent FTO glass as the substrate.It is revealed that the growth process of TNRs was controlled by the tunable hydrolysis rate,and a novel morphology sample with more surface active sites which restrains the directional migration of the photo-induced electrons was synthesized with the preferable hydrolysis rate.On this basis,the photoelectrode with heterojunction structure is further formed by incorporating with narrow band gap semiconductor Cu20.The comprehensive experiment results showed that the Cu2O/TNRs/FTO photoelectrode with unique appearance extends the light response range to the visible light region and successfully separates the photo-induced electron-hole pairs through the stable heterojunction interface,which greatly enhances the performance of photocatalytic hydrogen production via water splitting.(3)Dark blue Ti02 was synthesized by a safe and convenient electrochemical hydrogenation scheme,and the synergistic effect of graphene oxide on the production of Ti3+ ions and oxygen vacancies(Ov)in the bulk and surface during the reduction process was studied.Through the experiments on the research of the band structure,the valence band position and band gap width of the samples with different hydrogenated and reductive degrees were determined,and the photocatalytic mechanism of the self-doped samples which is highly consistent with the experimental results is proposed.(4)The photoelectrode Cu20/rG0/TNRs/FTO containing electron-bridging within semiconductor heterojunction interface was successfully prepared.The function of each component in the photocatalytic reaction was confirmed respectively,and a more considerable quantum efficiency was obtained compared with the previous work.In addition,a systematic study was carried out on the environment of the greatest influence on the hydrogen production performance of the new material,and the variation of hydrogen generation caused by the "space hindrance" effect aroused by the polarity of the sacrificial agent on the sample surface was expounded.