Preparation And Photocatalytic Performance Of Composite Semiconductor Based On Black TiO₂

Because countries are vigorously developing heavy industries and exploring new technologies,the excessive use of fossil fuels has brought about energy shortages and environmental degradation,so there has been a huge demand for renewable and carbon-free energy.As a near-endless source of clean energy,solar radiation has attracted widespread attention.Finding efficient ways to use solar energy has become a research hotspot in exploring new energy sources.Semiconductor photocatalytic technology is the most effective solution to break through the energy bottleneck due to its simple equipment,low cost,green non-toxicity,high efficiency and energy saving.Not only can hydrogen generated by decomposing water be an ideal clean energy,but it can also degrade organic pollutants to purify the water.Among many photocatalysts,titanium dioxide（TiO₂）has become one of the most promising materials due to its high efficiency and stability.However,the wide band gap（3.2eV）of TiO₂ and the easy recombination of photogenerated electron holes limit the photocatalytic performance.In order to solve the above problems and promote the application of TiO₂ in the field of photocatalysis,the morphology and performance of materials were modified in this paper.Firstly,the original materials of TiO₂ were prepared by three different synthesis methods,and the influence of grain structure and crystal relative photocatalytic performance was analyzed.Secondly,self-doping modification was carried out:the electrochemical surface was reduced to black TiO₂,resulting in oxygen vacancy defect and disordered surface of lattice.Ti³⁺was introduced to change the band gap width to improve the absorption of visible light.Then,external doping modification was carried out:MoS₂ was doped into the black TiO₂system by hydrothermal growth to form a composite semiconductor photocatalyst,which generated heterojunction and effectively improved the photocatalytic performance.SEM,TEM and EDS were used to analyze its microscopic composition and crystal phase structure,its crystal shape and elemental valence state were analyzed by XRD and XPS,its chemical and physical properties were analyzed by DRS,absorption spectrum,photocurrent and BET,etc.,and its photocatalytic performance was analyzed by photodegradation of rhodamine B solution and photodissociation of aquatic hydrogen.The main contents of the paper are as follows:（1）The micron-sized spherical H-TiO₂ particles were synthesized by hydrothermal method using tetrachlorobutyl titanate as the raw material;Synthesis of nanomaterials with Degussa P25 TiO₂ for commercial calciners;Freestanding TiO₂ nanotube arrays（F-TNTAs）were innovatively prepared by multi-voltage anodizing and the optimal performance was obtained by changing the ultrasonic time at 30min.After testing,f-tntas showed the best photocatalytic performance:73.3%Rh B was degraded within 30min.The photolysis rate was0.5208 mmol·g^-1·h^-1.（2）The three groups of materials were modified and reduced to BH-TiO₂,B-P25 and BF-TNTAs by using Na BH₄ as the reducing agent and argon as the protective gas in the vacuum tube furnace.After the photocatalytic performance was tested,BF-TNTAs showed the best performance and degraded 89.2%Rh B within 30 days in terms of photodegradation.The rate of hydrogen production in photolysis water was 10.953 mmol·g^-1·h^-1,which increased by 21 times.（3）The samples continue to doping modification,with sodium molybdate and thiourea as raw materials,by means of hydrothermal method of growth for three groups of black TiO₂ doped MoS₂,and through the adjustment of MoS₂ load（2%,3%,5%,7%）to explore the best ratio,the results showed that different samples in load 5%wt showing the best photocatalytic properties,moreover,the photocurrent and light absorption performance are improved obviously.In terms of photodegradation,BF-TNTAs/MoS₂ had the best performance,degrading 97.2%Rh B solution in 30min.Similarly,BF-TNTAs/MoS₂ with the best morphology in terms of photolysis had the highest hydrogen production rate,which was 19.0621mmol·g^-1·h^-1,with the highest improvement efficiency reaching 36.1 times.（4）in terms of material stability,spherical H-TiO₂ prepared by hydrothermal method had the best performance before and after modification;The stability of nanometer material P25 is in the middle.The stability of freestanding nanotubes F-TNTAs is general.In addition,the effects of photocatalytic time on the structural properties of materials were investigated and analyzed with SEM.