Preparation and photocatalytic performance of titanium dioxide/porous carbon nanofibers composite material
Objective With the widespread use of organic dyes,the residue of which have gradually become the main component of industrial wastewater and caused serious water pollution.As an environmentally friendly photocatalyst,titanium dioxide(TiO2)nanoparticles have been used in dye degradation,wastewater treatment and other fields due to their high photocatalytic activity,large specific surface area and easy preparation,but they also have problems such as wide band gap and difficult separation and recovery.Therefore,it is urgent to find a suitable carrier material to achieve effective separation and recovery of TiO2 without reducing its photocatalytic activity and stability.Method Porous carbon nanofibers(PCNF)were prepared by electrospinning,high-temperature calcination,and acid dissolution.Then anatase TiO2 was loaded onto its surface by secondary nucleation method to obtain photocatalytic TiO2/PCNF composites.The morphology,structure,composition,and light absorption properties of TiO2/PCNF nanocomposites were characterized by scanning electron microscopy,X-ray diffraction,X-ray photoelectron spectroscopy and UV-Vis diffuse reflection spectroscopy,and the photocatalytic properties of TiO2/PCNF nanocomposites were tested by degradation methylene blue(MB)solution.Results SEM results showed that TiO2 nanoparticles were uniformly loaded on porous CNF surfaces,while it was difficult to be loaded on smooth CNF surfaces.This showed that the mesoporous surface of carbon nanofibers was the key to the loading of TiO2.XRD results indicated that the three samples prepared,i.e.,TiO2,TiO2/PCNF and TiO2/CNF were of anatase phase TiO2.Compared with rutile phase and titanite phase,anatase phase TiO2 had better photocatalytic activity,so it was beneficial to improve the photocatalytic performance of TiO2/PCNF.The full spectrum of XPS showed that Ti,O,C,F and N elements existed in TiO2/PCNF composites,which further proved that TiO2 had been successfully loaded onto the surface of porous carbon nanofibers.The UV-Vis DRS results showed that significant redshift could occur when TiO2 was loaded onto both PCNF and CNF surfaces,which not only increased the utilization rate of visible light,but also reduced the band gap value.Brunauer-Emmett-Teller(BET)results suggested that the prepared TiO2/PCNF composites had mesoporous structures,and the specific surface area was as high as 331.9 m2/g,providing abundant active sites for adsorption and surface reaction.The photocatalytic tests showed that the removal efficiency of TiO2/PCNF composites was higher than that of the control group with the same TiO2 content.After 30 min illumination of TiO2/PCNF composite material,the removal rate of MB solution of 5 mg/L was 98.6％,and after 60 min illumination,the removal rate of MB solution could reach 99.6％.However,the removal rates of TiO2 and TiO2/CNF composites in the control group were only 93.3％and 73.2％for MB solution after 30 min illumination.After repeated use for 5 times,the removal rate of TiO2/PCNF on MB solution remained at 95.0％.All these indicated that TiO2/PCNF composites have excellent photocatalytic and reusable properties.Conclusion The TiO2/PCNF composite was successfully prepared by secondary nucleation method,and the composite had excellent photocatalytic and reusable properties.Compared with CNF,it was found that PCNF with mesoporous structure was more conducive to the loading of TiO2.The improvement of photocatalytic performance of TiO2/PCNF composites was mainly attributed to the following reasons.①All the prepared TiO2 were anatase phase,which has better photocatalytic activity than rutile phase and plate titanite phase.②The TiO2/PCNF composite increased the response range of TiO2 to visible light,which was conducive to improve the utilization rate of TiO2 for visible light.③PCNF had excellent electrical conductivity,which was conducive to accelerating the separation of TiO2 photogenerated electrons and holes.④PCNF had a large specific surface area,which providing more active sites both for MB adsorption and surface reactions.
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