Study On Structure Regulation And Structure-activity Relationship Of WO₃-based Photocatalyst

The rapid development of economy and industrialization has caused two crises of environmental pollution and energy shortage.Semiconductor photocatalytic technology has attracted wide attention due to its low cost,green and efficient characteristics,and has become one of the most active fields of scientific research.Tungsten trioxide（WO₃）is widely used in gas sensing,photocatalysis and other fields because of its excellent photoelectric characteristics and its tunable band structure and more positive valence band（VB）edge.However,the narrow light absorption range and the high recombination rate of photogenerated electrons（e^-）and holes（h⁺）restrict its practical application.Therefore,morphology regulation,defect engineering,element doping,heterojunction construction and other modification methods are used to regulate the separation of WO₃photocarriers and improve their photocatalytic performance.Among the numerous studies,there are few systematic studies on the structural regulation of WO₃-based photocatalysts and their structure-activity relationship,and further studies on the mechanism of their enhanced photocatalytic performance are needed.The main research contents are as follows:First of all,one dimensional（1D）structure can control the directional electron transport and pation method.The phase composition and morphology of WO₃nanofibers were characteromote the efficient separation of photogenerated electron-hole.One-dimensional WO₃ nanofibers were prepared by electrostatic spinning method and post-calcinrized by XRD,SEM and TEM.It was found that smooth WO₃nanofibers with a diameter of 100-200nm and a large specific surface area could be successfully synthesized.XPS,uv-vis-drs,PL and EIS were used to characterize the photoabsorption and photochemical properties of the catalyst.The photocatalytic degradation of MB solution was used to evaluate the photocatalytic performance of the catalyst.The results showed that after 120min of photodegradation,the degradation rates of MB at 500℃,600℃,700℃and 800℃were 52%,65%,41%and 34%,respectively.The best sintering temperature was 600℃.Secondly,we explored the effect of PVP content on the catalytic activity.The results showed that the W600-2:1 sample prepared when PVP content and WCl₆ ratio was 2:1 had a degradation rate of 70%under 120min of light,showing a good photocatalytic activity.Secondly,Element doping can introduce impurity levels into the semiconductor,regulate the electronic band structure,reduce the band gap value and broaden the absorption range of visible light.A series of transition metal-doped TM-WO₃（TM=Cr,Co,Fe,Ni）photocatalysts were prepared by hydrothermal method.The photocatalytic activity of TM-WO₃ photocatalysts was evaluated by photocatalytic degradation of MB solution.The results showed that after visible light irradiation for 120min,the degradation rates of original WO₃,Cr-WO₃,Fe-WO₃,Co-WO₃ and Ni-WO₃ catalysts for MB were 65%,62%,67%,77%and 50%,respectively.Combined with the characterization results of XPS,EIS and PL,Co-WO₃showed excellent photoelectric properties.It is found that the highly crystalline Co-WO₃ material has the best photocatalytic activity when the metal ions such as Cr³⁺,Co²⁺,Fe³⁺and Ni²⁺are doped in the same period.Finally,a novel visible-light driven heterojunction WO₃/AgI photocatalyst was prepared by hydrothermal and precipitation methods.The photocatalytic performance of the catalyst was investigated using simulated wastewater pollutants such as MB,RhB and tetracycline solution.The results showed that the degradation rate of RhB solution with 2:1 WO₃/AgI heteroconjugation could reach 99%and the degradation rate of tetracycline could reach 87%after visible light irradiation for 60 min,compared with the original AgI and WO₃.The degradation of MB solution was not obvious.The catalyst activity did not decrease after 4 cycles.The enhanced activity is attributed to the Z-type heterojunction structure formed between AgI and WO₃,which can promote the efficient separation of photogenerated carriers in the heterojunction.