Photocatalytic Performance On Dye Wastewater Of Nano MoS₂,TiO₂ And Its Composite

Nano TiO₂ and MoS₂ have the advantages of high photocatalytic degradation ability,non-toxic,no secondary pollution and cheaper.It received the widespread attention in the field of printing and dyeing wastewater treatment.In this paper,in order to analyze the adsorption and degradation efficiency of organic dyes in visible light,the anatase TiO₂ nanobelts,MoS₂ nanoflowers,MoS₂ nanorods and TiO₂/MoS₂ heterostructure photocatalysts were used.The concrete research content were as followed:（1）The models of rutile TiO₂,anatase TiO₂,single layer MoS₂ and TiO₂/MoS₂ were builded on the basis of the CASTEP module.The band gap of rutile TiO₂,anatase TiO₂,single layer MoS₂,TiO₂/MoS₂ complex were 1.849 eV,2.109 eV,1.506 eV and 1.96 eV respectively.The band gaps of TiO₂/MoS₂ were between TiO₂ and MoS₂.From the DOS and PDOS of TiO₂/MoS₂ complex,we know the conduction band bottom was determined by hybridization of Mo（3d）orbit,Ti（3d）orbit and S（3p）orbit,the valence band tap was determined by hybridization of S（3p）orbit,O（2p）orbit and Mo（3d）orbit.The calculated value of band gap is less than the theoretical value,due to the defects of simulate the local density approximation.This experiment used the same contrast method and under the same condition,so tiny gap didn’t affect the final results.（2）TiO₂ nanobelts,MoS₂ nanoflowers,MoS₂ nanorods and TiO₂/MoS₂ heterostructure photocatalysts were synthesized through a simple hydrothermal procedure.From the SEM images we can see that,MoS₂ nanoflowers were about 350 nm in particle diameter,the MoS₂ nanorods were about 300 nm in particle diameter and about 3000 nm in length,the TiO₂ nanobelts were about 100-200 nm in width,20 nm in thickness and 2 μm in length.TiO₂/MoS₂ heterostructures were about 150 nm in width,20 nm in thickness and 2 μm in length,coated with MoS₂ nanoflowers which is 150nm-300 nm in particle diameter.（3）X-ray diffraction pattern of nanophotocatalyst showed that,the crystals were high crystallinity and single crystal phase.The diffraction peak of TiO₂/MoS₂ heterostructures at 13.9°,25.3°,34.5°,37.8°,48.1°,53.9°,60.4° and 62.8°.The materials contained diffraction peak of anatase TiO₂ and MoS₂ at the same time.This means that TiO₂/MoS₂ heterostructures contained anatase TiO₂ and MoS₂.（4）UV-vis absorption spectra of nanophotocatalyst showed that,TiO₂ nanobelts and TiO₂ p25 had a significant absorption in wavelength shorter than 350 nm.The MoS₂ nanoflowers,MoS₂ nanorods and TiO₂/MoS₂ heterostructures bad a significant absorption at 300nm-800 nm in wavelength.The MoS₂ nanoflowers bad one peaks which is located at 485 nm.The MoS₂ nanorods had two peaks which were located at about 505 nm and 678 nm.The TiO₂/MoS₂ heterostructures had three peaks which were located at about 389 nm,470nm and 630 nm.The absorption in the visible light region of TiO₂/MoS₂ heterostructure was obviously enhanced,compared to the anatase TiO₂ nanobelts,TiO₂ p25,MoS₂ nanoflowers and MoS₂ nanorods,and analysis the reason of it.（5）We choosed rhodamine B,methylene blue,methyl orange to photocatalytic adsorption and degradation experiment.The experimental resulted show that the of TiO₂/MoS₂ heterostructure photocatalysts adsorption and degradation efficiency of rhodamine B,methylene blue,methyl orange were the highest,compared to anatase Ti O₂ nanobelts,TiO₂ p25,MoS₂ nanoflowers and MoS₂ nanorods,which about 99.62%,96.41% and 87.45%.In the final,we analysis the reasons for this situation.