| Nowadays,dealing with water pollution and finding alternative sources of clean energy have been globally advocated,due to the serious problem of water pollution and energy crisis.Photocatalysis has attracted the attention of researchers because of its environmentally friendly,high efficiency and no secondary pollution.Titanium dioxide(TiO2)is widely used for its low price and stable chemical properties.However,TiO2 only responds to ultraviolet light and owns low utilization rate of solar energy.In contrast,the narrow band gap of cadmium sulfide(CdS)makes it responsive to visible light and has high utilization of solar energy.However,it is prone to photocorrosion during the photocatalysis,reducing photocatalytic activity and causing secondary pollution.At present,core-shell photocatalysts have attracted much attention in the field of photocatalysis due to its unique structure and excellent photocatalytic activity.By means of yolk-shell and fiber-like structure,combined with the respective performance advantages of CdS and TiO2.The light response range of TiO2 is broadened,CdS is protected from photocorrosion and photocatalytic activity is enhanced.At the same time,the fiber-form photocatalysts are prone to recovering.Yolk-shell CdS@void@TiO2 nanospheres(NSPs)and their nanofiber films were prepared,and their crystal phases,microstructure,thermodynamic properties,optical properties and photocorrosion resistance were characterized and analyzed.Methylene blue(MB)degradation experiments and hydrogen production experiments were carried out to study its degradation and hydrogen production performance.Firstly,CdS core was synthesized by solvothermal method,and a polypyrrole(PPy)layer(CdS@PPy)was formed on the surface of CdS particles by oxidative polymerization.Tetrabutyl titanate(TBT)was employed as the titanium source and polyethylene glycol(PEG-20000)was used as pore-forming agent.Cadmium sulfide@polypyrrole@hydrogen titanate(CdS@PPy@H4TiO4)was fabricated by sol-gel method,and followed by calcination.After calcination,PPy layer and PEG were removed to form the intermediate void and the porous TiO2 shell.The results show that the energy gap of CdS@void@TiO2 NSPs is 2.9 eV,CdS@void@TiO2 NSPs can respond to light region between 200 and 550 nm.After 3 h of exposure under visible light,the dye removal efficiency of CdS@void@TiO2 NSPs was 93.72%,and the hydrogen evolution rate was as high as 1893.5 umol·g-1·h-1.The photocorrosion phenomenon of CdS is significantly reduced by protection of TiO2 shell and the intermediate void can provide more active sites to improve the photocatalytic degradation and hydrogen evolution performance.Secondly,in order to overcome the issue of recovery of NSPs in slurry,polyacrylonitrile(PAN)was used as the fiber carrier,the NSPs were made into nanofiber film(NFF)by electrospinning techinique.After calcination PAN carrier can be removed and the necklace-like fiber was residued.Subsequentally,PPy thin film was coated by vapor deposition.Finally,PPy-coated CdS@void@TiO2 photocatalytic nanofiber film was obtained.The results show that PPy-coated CdS@void@TiO2 NFF(after PPy covering)can respond to light in the range of 200-800 nm.After 3 h of visible light irradiation,dye removal efficiency of CdS@void@TiO2 NFF(after PPy covering)reached to 95.78%,and the hydrogen evolution rate was as high as 654.73 umol·g-1·h-1,showing excellent degradation and hydrogen evolution performance,as well as good photocorrosion resistance.CdS@void@TiO2 NFF(after PPy covering),in fiber-like form,is convenient for recycling and has a great potential in environmental protection and clean energy production. |
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