Study On Preparation And Modification Of Nano-TiO₂ Based Composite Photocatalysts

Energy crisis and environmental pollution have become severe challenges for all countries in the world,and seeking green and sustainable new energy is an important measure to solve this problem.Solar energy is widely concerned because of its universality and accessibility.The conversion of solar energy into electrical and chemical energy is a hot research topic in the energy field,in which semiconductor materials have always been the core of energy conversion.Composite materials based on nano-TiO₂have excellent performance in solar cells,photocatalytic degradation of pollutants,and water splitting to produce hydrogen.One-dimensional TiO₂nanorod array(TNR)has attracted much attention in many morphologies due to its dense and ordered structure.In this thesis,highly ordered TNR arrays were first prepared on FTO conductive glass by hydrothermal method.After that,the TNR arrays were modified by noble metal deposition and narrow band gap semiconductor compounding.The surface morphology structure,photoelectrochemical and photocatalytic properties of the composites were investigated.The details of the study are as follows:(1)In the experiments,Ag/MoS₂/TNR ternary composite photocatalysts are prepared by hydrothermal and photodeposition methods.The morphology,microstructure,optical,photoelectrochemical and photocatalytic properties of the samples are characterized.The experimental results showed that the Ag/MoS₂/TNR heterostructured arrays exhibited the best performance when the reaction time is 12 h.In transient photocurrent and photocatalytic tests,Ag/MoS₂(12h)/TNR exhibit the best photocurrent density(120?A/cm²)and photocatalytic efficiency(75%),which are 12 and 5 times higher than those of bare TNR,respectively.The excellent photoelectrochemical and photocatalytic properties can be attributed to the plasmon resonance effect of Ag nanoparticles and the presence of inter-semiconductor heterostructures,which not only enhance the absorption of visible light by the sample but also accelerate the transfer of photogenerated carriers across the interface.Therefore,Ag/MoS₂/TNR materials have potential application value in the fields of photoelectric conversion and photocatalysis.(2)Novel double Z-scheme Bi₂S₃/BiVO₄/TiO₂(BVT)heterostructured photocatalysts were prepared by continuous hydrothermal methods.In situ conversion of BiVO₄/TiO₂(VT)binary photocatalysts to BVT ternary photocatalysts with large optical absorption coefficients.Compared to TNR arrays,BVT photocatalysts extend the light absorption range to near-infrared with consistently high absorption intensities.Photoelectrochemical tests demonstrate that BVT(4)has the best transient photocurrent(110?A/cm²),which is approximately 11 times higher than that of TiO₂(10?A/cm²).The photocatalytic performance of all samples was investigated by degrading methyl orange(MO)under visible light irradiation.The results show that BVT(4)possesses the best degradation efficiency(76.3%)which is about 4 times higher than that of bare TNR(19.7%).The outstanding photoelectrochemical and photocatalytic performance can be attributed to the double Z-scheme charge transfer mechanism,which effectively promotes the separation and transfer of electron-hole pairs resulting in a strong redox activity of the accumulated charge on the different semiconductors.This novel double Z-scheme heterostructured photocatalyst has excellent performance,which is an important guideline for the design and preparation of TiO₂-based photocatalytic materials.