The Preparation And Performance Of Photoconcentration-oriented Photocatalysts

Today's society is a new era of high speed and high demand.The two problems of energy and environment are undoubtedly the key issues related to the sustainable development of human beings.However,with the development of industry,the problems of environmental pollution and energy shortage are becoming more and more serious.Semiconductor photocatalyst has gradually become an effective method to solve these two problems because of its ability to use solar energy to realize the degradation of and energy conversion of pollutant and the conversion of energy.The current development of photocatalysts has low utilization rate and quantum efficiency of sunlight,especially the photocatalytic activity is not high enough,and the pollutants cannot be completely degraded in a short time.At present,it is urgent to develop new and efficient photocatalyst,so that photocatalytic technology can better meet the needs of practical application.Current research shows that semiconductors absorb photons to generate electron-hole pairs,the separation of electron-hole pairs,and electron-hole pairs reach the surface to participate in reactions or transfer through external circuit,each process has a direct impact on the efficiency of solar energy conversion.The control of the photocatalyst interface can effectively improve the catalytic performance,including the optical absorption interface,the carrier excitation transfer interface and the catalytic reaction interface.Based on this,we start with the interface control of the catalyst,rationally design and control the interface of the semiconductor,and prepare a TiO₂ photocatalyst with light-enrichment performance,combined with semiconductor composite,precious metal modification and photovoltaic synergistic technology,to study the relationship between the three characteristics of material interface,photogenerated charge behavior and photocatalytic performance,provide theoretical and experimental basis for the design and preparation of high-efficiency photocatalytic materials.The main work can be divided into following three parts.?1?Preparation of highly dispersed TiO₂ and study on its hydrogen production performance.The preparation of highly dispersed TiO₂ nanocrystals has a larger specific surface area,enhances the interaction between the catalyst surface and photons,and exhibits excellent performance in photocatalytic degradation of pollutants.By the microwave heating treatment,organic substances on the surface of the catalyst are carbonized by the absorption of microwaves,the removal of organics is achieved while effectively preventing catalyst agglomeration.Through modification of the metal Pt,the Schottky barrier formed at the semiconductor-metal interface promotes the migration of electrons to the metal Pt,thereby suppressing the recombination of charges and ultimately increasing the efficiency of the reaction.The hydrogen production rate of prepared Pt/TiO₂ reached 35.5 mmol g^-1 h^-1 under ultraviolet light.?2?Preparation of yolk-shell hierarchical structure TiO₂ and study on its degradation of pollutant.Based on the solvothemal synthesis,TiF₄ as titanium source and fluorine source,organic alcohol as co-solvents,the multi-structure and special facets exposed yolk-shell TiO₂ are obtained.The yolk-shell hierarchical structure can improve the utilization of light by multiple reflections of light.The g-C₃N₄/TiO₂ composite photocatalyst was prepared by the incorporation of g-C₃N₄ implanted on the yolk-shell TiO₂ via chemical vapor deposition with dicyandiamide as a precursor.The self-built electric field at the heterojunction interface plays a dominant role in the separation of photogenerated charge.At the same time,the 2D/2D interface contact mode effectively increases the area of the heterojunction and improves the separation efficiency of photogenerated carriers.The experimental results show that the 3D hierarchical structure g-C₃N₄/TiO₂ composite photocatalyst has good photocatalytic activity for the degradation of Rhodamine B solution and phenol solution.?3?Preparation of iridescent TiO₂ films and its optoelectronic properties.A facile approach was developed to synthesize iridescent TiO₂ films consisted of assembled TiO₂ nanosheets by solvothermal alcoholysis.Firstly,a layer of rutile TiO₂protective layer was coated on the surface of the titanium metal sheet,and then the self-assembly deposition of the anatase TiO₂ nano-sheet was performed.The experimental results show that the double-layered TiO₂ thin film can effectively prevent the direct contact between the substrate and the electrolyte to form a short circuit,and the photoelectrochemical performance of the thin film material is significantly improved.At the same time,the design of the heterojunction forms a self-built electric field to further improve the separation efficiency of the photogenerated charge,and thus the optical properties of the TiO₂ film are well improved.The graphite C₃N₄ is modified on the surface of the film by a chemical vapor deposition method.The film surface with grating structure,which can selectively absorb specific wavelengths of visible light.The trapped visible light forms an enhanced optical field to improve the light utilization of graphite C₃N₄ and the utilization of visible light by the film is further improved.The prepared g-C₃N₄/TiO₂ iridescent film showed excellent optoelectronic performance in synergistic catalytic degradation of organic pollutants.