Study On Preparation,Characterization,and Photocatalytic Application Of The Nano-TiO₂ And Its Composites

Semiconductor photocatalysis has become one of the hot topics in the 21st century due to its promising application potential in clean energy preparation and deep purification and mineralization of environmental pollutants.Among lots of photocatalytic materials,TiO₂ has been considered as the most promising photocatalyst due to its excellent physical and chemical properties such as lower price,stability,high efficiency and solar energy as the driving force.However,TiO₂ has the defects of lower light absorption efficiency and electron-hole pairs separation efficiency,which is difficult to meet the social demand for photocatalytic technology and restricts the sustainable development of society.Therefore,it is of great significance to develop a new and efficient Ti'O₂ composite photocatalytic system.Based on the above debate,this paper aimed to improve the photocatalytic performance of TiO₂ and carried out a series of modification studies on the defects of TiO₂.The specific research contents were as follows:?1?The preparation of high effective P-TiO₂ aqueous sol system at low temperature.P-TiO₂ sol with high photocatalytic activity was prepared by the gel-sol method with phosphoric acid as the phosphorus source,and the phase structure,light absorption performance and valence bond structure of P-TiO₂ were characterized and analyzed.The analyses and tests show that P doped can not change the crystal structure of TiO₂,but improved its crystallinity.In addition,the existence of P in lattice of TiO₂ was P-Ti-O.The UV-Vis spectra confirmed that P doping caused the the blue shift of the absorption edge of TiO₂,further increased the redox activity,which was the fundamental reason for the improvement of photocatalytic activity of P-TiO₂.As shown as the photocatalytic performance test,when the molar radio of P and Ti was 1:15,the photocatalytic performance reached the best and the kinetic constant was up to1.3177h^-1,which was 5.4 times of the commercial P25.?2?The preparation of high effective B-TiO₂ aqueous sol system at low temperature.Because the particles generated by P-TiO₂ sol system was larger and tended to form unstable state,therefore B³⁺was selected to replace P⁵⁺in this paper to doped TiO₂.Analyses and tests show that B doping also does not change the crystal structure of TiO₂.With the condition of appropriate doping concentration,the existence of B in the lattice of TiO₂ was B-O-Ti structure,which caused the red shift of the absorption edge and further expanded the response range to light.The photocatalytic performance test with methyl orange as the template of organic pollutants showed that when the molar radio of B and Ti was 1:6,the photocatalytic performance reached the best,and the kinetic constant was 0.528h^-1,which was 4.4 times higher than commercial P25.?3?The construction of CNQD_s/B-TiO₂ composite photocatalytic system.The absorption range of B-TiO₂ has been expanded,but the quantum yield still need to be further improved.Therefore,in this paper,CNQD_s/B-TiO₂ composite heterojunction photocatalyst was prepared by the modification of CNQD_s on the surface of B-TiO₂.The analyses and tests showed that the existence of CNQD_s expanded the absorption range of the composite system,and the heterojunction between CNQD_s and B-TiO₂improved the efficiency of electron migration,which improved the photocatalytic performance of the system.The photocatalytic performance test with methyl orange as the template of organic pollutants showed that when the amount of CNQD_s was 0.8ml,the photocatalytic performance reached the optimal value,and the kinetic constant was0.6885h^-1,which was 1.3 times higher than that of B-TiO₂,and the photocatalytic performance was significantly improved.?4?The construction of GQD_s/B-TiO₂ composite photocatalytic system.GQD_s was acknowledged as excellent photocatalyst auxiliary.Furthermore,GQD_s/B-TiO₂composite photocatalytic system was prepared by a simple physical mixing method.The results showed that GQD_s/B-TiO₂ composite system had better photocatalytic performance than CQD_s/B-TiO₂ system.On the one hand,the heterojunction between GQD_s and B-TiO₂ accelerateed the surface electron migration rate and improved the quantum yield.On the other hand,the large?bond structure of GQD_s improved the adsorption performance of the whole photocatalytic system to organic pollutants,which was conducive to the rapid progress of surface photochemical reactions.The photocatalytic performance test of methyl orange as the template of organic pollutants showed,when the volume ratio of GQD_s and B-TiO₂ was 8:1,the kinetic constant reaches 1.5018h^-1,which was about 2.86 times of B-6,GQD_s/B-TiO₂ had a good photocatalytic performance.