Study On Preparation And Performance Of Titanium Dioxide-Based And Zinc Oxide-Based Semiconductor Photocatalysts

TiO₂ and ZnO have been widely used due to their low price,non-toxity,high chemical stability,high photocatalytic activity,light corrosion resistance,and strong oxidation ability.However,the large band gap of TiO₂ and ZnO,high recombination rate of photogenerated electrons/holes and harsh physical conditions during preparation,which limit the application of TiO₂ and ZnO.In order to improve the harsh preparation conditions,this topic studies the crystalline TiO₂ is prepared under low temperature and normal pressure,a large number of oxygen vacancies are implanted into semiconductor photocatalysts.Basis on this,oxygen vacancies are extended to other metal oxides.The specific research results are demonstrated as following:(1)The aqueous Peroxo-Titanium-Complex precursor was synthesized based on the peroxidation method,and crystalline TiO₂-based composite photocatalyst was prepared by reducing peroxide groups though redox method at low temperature and normal pressure.Yellow TiO₂ containing abundant oxygen vacancies was synthesized by using hydroxylamine hydrochloride as the reducing agent at 25?,and the results showed that the band gap of yellow TiO₂ was 2.9 eV.The rate of RhB decomposition under ultraviolet light and visible light and the NO removal efficiency of yellow TiO₂ were enhanced.Regulate the photocatalyst performance by adjusting the type of reducing agent at the same temperature.Due to the doping of N element and the surface groups,TiO₂ prepared by reduction of hydroxylamine exhibited the best photocatalytic activity.Simultaneously,The TiO₂/RGO composite material was successfully prepared.Under the synergistic effect of RGO and defects,the photocatalytic NO degradation rate and photocatalytic nitrogen fixation efficiency of TiO₂/RGO was increased.(2)The TiO₂/Nb₂O₅ composite photocatalyst was synthesized by thermal decomposition method.The relationship of the molar ratio of Ti/Nb on the performance of TiO₂/Nb₂O₅ composite photocatalyst was investigated.XRD results showed that TiO₂ was anatase phase,and Nb₂O₅ was amorphous.2Ti/1Nb showed the highest photocatalytic activity due to the fact that the introduction of Nb5+and Ti3+,and the heterostructure formed by TiO₂ and Nb₂O₅.(3)In order to implant a large number of oxygen vacancies,TiO₂ with different colors was successfully synthesized though sol-gel hydroxylation method by using yellow TiO₂ as the precursor under different conditions.The effect of calcination atmosphere(Air,N2 and Ar)and tempreture on oxygen vacancy content and photocatalyst performance was studied.The photocatalyst was synthesized at 500? and argon atmosphere exhibited excellent visible light absorption and photocatalytic activity on the effect of oxygen vacancies and Ti3+.Simultaneously,the performance of TiO₂/ZnO composite photocatalyst has been studied.The results showed that Anatase TiO₂/Rutile TiO₂/ZnO homojunction and heterojunction composite structure was formed on the composite of TiO₂ and ZnO,which not only expanded the photoresponse range of the photocatalyst,but also realized effective charge separation and transfer through the built-in electric field,thereby improving the photoelectric performance of the composite material.(4)The porous g-C3N4 containing nitrogen vacancies and cyano groups was successfully synthesized through one-step method by using urea as the precursor.Due to the introduction of nitrogen vacancies and cyano groups,the rate of RhB degradation,NO degradation efficiency and the nitrogen fixation performance of VN-g-C3N4 significantly improved.EPR capture experiment proved that 1O₂ was the main active group for photocatalytic reaction.The oxygen vacancy-TiO₂/carbon vacancy-g-C3N4 composite photocatalyst was prepared on the basis of the double defects strategy.Benefit from the synergistic effect of carbon vacancy,oxygen vacancy and heterostructure,the NO degradation efficiency of VO-TiO₂/Vc-g-C3N4 was 3.5 times higher than that of VO-TiO₂ and 2.2 times higher than that of VC-g-C3N4;the nitrogen fixation performance was about 3.8 times and 3.1 times higher than that of VO-TiO₂ and VC-g-C3N4.EPR capture experiments proved that 1O₂ and ·OH were the main active groups in photocatalytic reactions.(5)Oxygen vacancy was introduced into other oxides through oxygen vacancy control strategies.ZnO photocatalyst containing surface oxygen defects was prepared by the redox method.And the influence of the concentration of the reducing agent on the photocatalytic performance was studied.When the concentration reached to 0.8 mol/L,the results of TEM and EPR proved disordered layers on the surface and the formation of oxygen vacancies.The efficiency of NO photodegradation for the optimal ZnO was about 12 times higher than that of W-ZnO without surface oxygen deficiency;the nitrogen fixation performance was 13 times higher than that of W-ZnO.