Design And Preparation Of ZnO,TiO₂ Based Nano-composite Film For Their Efficient Photocatalysis

In recent years,with the rapid development of economy,energy shortage and destruction of ecological environment have become the focus of human attention.Because of the serious damage to the ecological environment,the earth desertification,the eutrophication of water and the exhaustion of mineral resources have appeared.It is important to sustainable development of society that seeking environmentally friendly renewable energy.Hydrogen is currently recognized as a clean energy source,and the sunlight is an inexhaustible ideal energy,so the technology of photocatalytic hydrogen production has become a hot spot today.Photocatalytic hydrogen production can not only solve the problem of energy shortage,but also is friendly to the environment.In this thesis,three kinds of photocatalytic composite films were prepared by using ZnO and TiO₂ to improve their photocatalysis/photoelectrochemical water splitting hydrogen production properties and detect heavy metal ions.Three kinds of photocatalytic composite films were fabricated on the FTO conductive glass,including CdS/ZnO,PbS/CdS/ZnO and CdS/HTNRs.They were characterized by scanning electron microscopy?SEM?,transmission electron microscopy?TEM?and X-ray powder diffractometer?XRD?for morphology,structure and crystal morphology.The composition and optical properties were further analyzed by X-ray photoelectron spectroscopy?XPS?,fluorescence spectroscopy?PL?and ultraviolet visible diffuse reflectance spectroscopy?DRS?.The photoelectrochemical tests were measured using an electrochemical workstation.The main contents are as follows:?1?ZnO seeds were prepared on spin conducting glass?FTO?by spin coating and calcined in air.Then the ZnO nanorod array was continued to grow on FTO with ZnO seeds by hydrothermal method.Finally,CdS quantum dots were deposited on ZnO nanorods by solvothermal method,and the CdS/ZnO hollow structure photocatalytic composite was obtained.XRD results show that the crystal structure of ZnO is six wurtzite.SEM and TEM show that ZnO is a hollow nanorod structure,and CdS is uniformly covered on the surface of ZnO.The results of photocatalytic hydrogen production showed that the hydrogen yield of 5 h was 10 mol cm^-1.The hydrogen production of the sample after Pt was increased by7.7 times.As a co-catalyst for hydrogen production by photodissociated water,Pt was a high-speed channel for photoinduced electron transfer,which enhanced the separation of electrons and holes,thus effectively improving the hydrogen production performance of photodissociated water,and the amount of hydrogen production reached to 3.4 mL h^-1.?2?CdS/ZnO photocatalytic composites were obtained by water heat and solvothermal method.The PbS quantum dots were continuously deposited on CdS/ZnO nanotube arrays by traditional continuous ion deposition?SILAR?,and the PbS/CdS/ZnO nanomaterials were obtained.TEM results show that the CdS/ZnO nanostructure is transformed from nanorod structure to nanotube structure.At the same time,a simple device for hydrogen production by photoelectric water splitting was designed to collect H₂ and read the amount of hydrogen production in real time.Under the simulated sunlight,the photoelectric hydrogen production of PbS/CdS/ZnO increased significantly than that of CdS/ZnO,and the average hydrogen yield of 3 h reached 8 mL h^-1.?3?The TiO₂ nanorod array was grown on the FTO conductive glass by hydrothermal method.The hydrogenated TiO₂ nanorod array?HTNRs?was obtained by hydrogenated calcination.Finally,the CdS quantum dots were deposited on HTNRs by continuous chemical water bath?CBD?,and the photoelectric sensor materials of the CdS/HTNRs composite nano film were obtained,and the different CdS deposition was obtained.The effect on the photocurrent of the sample is obvious.The three electrode system was used to detect Cu²⁺with different concentrations under visible light irradiation.XPS shows that in the Cu²⁺solution,the Cu_xS formed on the surface of the CdS/HTNRs sensor can be used as the complex site of the CdS photogenerated carrier,causing the decrease of the photocurrent under the visible light.The photocurrent under Cu²⁺free condition is I_before,and the photocurrent after adding Cu²⁺is I_after,(I_before-I_after)/I_before has a good linear relationship with the concentration of Cu²⁺in a certain range.A Cu²⁺photoelectrochemical sensor with excellent performance is designed.The sensor has a wide detection range?0.04-164?M?and a lower detection limit?0.004?M?.