Morphology Controllable Preparation And Photocatalytic Properties Of Nano-copper And Its Oxide Photocatalysts

Using the solar energy to solve the growing global environmental problem and energy crisis is a major global task in the future.The development and utilization of visible light-driven photocatalysts with novel morphology and structure is a new research hot spot in recent years.In this thesis,with non-noble metal copper and its oxide materials as the research subjects,a series of visible light-driven photocatalysts with special morphologies and structures have been prepared controllably by designing preparation methods.The effect of preparation condition on morphology and structure has been studied.The photocatalytic performances of the prepared materials with different morphologies have been tested.Moreover,we proposed the possible mechanism of photocataytic H₂ production over these materials under visible light irradiation.The main contents and conclusions of this thesis are as follow:?1?nanostructured Cu with different morphologies were successfully prepared by electrodeposited method on FTO glass substrate and applied for photocatalytic H₂ production from water.We emphatically analyzed the influence of electrodeposition potential,electrodeposition time and surface area on the photocatalytic performance of Cu/FTO in details and found that Cu/FTO with different morphologies showed an enhancement of photocatalyic H₂ production efficiency compared to that of bare FTO glass substrate.The sample with spherical morphology shows the highest visible-light photocatalytic activity and the cumulative hydrogen yield reached 30mmol·cm^-2 for an illumination time of 6h.A possible mechanism of Cu/FTO photocatalytic water-splitting for hydrogen production was proposed based on our experiments and the previous work.The Cu/FTO is proved to be stable and reusable through the cycle experiments and comparison of XRD,XPS patterns of Cu/FTO-600s before and after the catalytic reactions.?2?Cu/Cu₂O/FTO composite materials with three different morphologies and visible-light photocatalytic activity were prepared onto FTO glass substrate by a facile one-pot hydrothermal reaction strategy.The composition,morphology and spectroscopy properties of the samples were characterized by X-ray diffraction?XRD?,scanning electron microscopy?SEM?,energy-dispersive X-ray spectroscopy?EDS?,transmission electron microscope?TEM?,X-ray photoelectron spectroscopy?XPS?,Fourier transform infrared?FTIR?spectroscopy and diffuse reflectance spectrum?DRS?,respectively.Results indicate that the states of copper in Cu/Cu₂O/FTO composite materials are Cu?0?and Cu?I?.The morphologies of the samples could be changed from truncated octahedron to hex-pod-like whisker as the reaction time increases.In addition,Graphite may be present on the surface of the Cu/Cu₂O/FTO which can protect Cu from being oxidized.Under visible-light radiation,the as-obtained Cu/Cu₂O/FTO exhibits excellent ability in the photocatalytic splitting of water to produce H₂.The sample with special morphology?hex-pod-like whisker?shows the highest visible-light photocatalytic activity with the hydrogen evolution rate of 11.5?mol·cm^-2·h^-1.Moreover,the photocatalytic mechanism was also proposed.Specifically,due to SPR excitation,photoexcited state of Cu produces hot electrons.These hot electrons will flow from SPR band of Cu to the CB of FTO by two different pathways:?1?the direct electron transfer from SPR band of Cu to the CB of FTO;?2?electron transfer from SPR band of Cu to the CB of FTO via Cu₂O.