Fabrication Of WO₃-based Photocatalysts Based On Chemical Bath Deposition Method And Their Properties Study

As a transition metal oxide semiconductor,tungsten oxide(WO₃)is considered a promising material in photocatalysis for its great properties such as high stability in acid condition,nontoxicity and visible-light response ability.This work focused on the fabrication of WO₃-based photocatalysts by chemical bath deposition(CBD)method and study on their photocatalytic properties.The method used was facile and suitable for large-scale synthesis.By controlling the amount of surfactant and complexing agent,the morphology and band structure of WO₃ were changed,the carrier recombination and transmission ability were studied,WO₃-based photocatalysts with higher visible-light response and photocorrosion resistance were constructed.In this work,many methods were used to characterize the crystal structure,morphology,chemical component,specific surface area,photoresponse,photocatalytic mechanism and formation mechanism.Full details are below:1.Synthesis of WO₃-FTO film and study on its properties.WO₃ film was uniformly fabricated on the surface of fluorine-doped Sn O₂(FTO)conductive glass by facile CBD method.The morphology,scale and chemical component were characterized by many methods.The amount of H₂C₂O₄ was changed during the CBD process,when the molar ratio of Na₂WO₄/H₂C₂O₄ was 1:2 the as-prepared WO₃-FTO-1showed an intersected nanosheets morphology.When the molar ratio of Na₂WO₄/H₂C₂O₄came to 1:3,the obtained WO₃-FTO-2 was composed of thinner intersected nanosheets which were perpendicular to the FTO basement.The as-prepared WO₃-FTO films both showed a high photocorrision resistance and photoresponse ability.Arritubed to the thinner thickness and smaller nanosheets,the carrier recombination of WO₃-FTO-2 was much lower than WO₃-FTO-1.The stable photocurrent density of WO₃-FTO-2 was 1.2 times that of WO₃-FTO-1.2.Fabrication of porous WO₃ nanosheets and its improvement in photocatalysisSquare H₂WO₄ nanosheets were fabricated by CBD method with the assistance of sodium dodecylbenzene sulfonate(SDBS)surfactant.After annealing H₂WO₄ nanosheets turned into porous WO₃ nanosheets.The as-synthesized porous WO₃ nanosheets had a pore size distribution from 20-60 nm.Compared with bulk WO₃,porous WO₃ nanosheets showed a reduction of bandgap.Moreover,the photocurrent density of porous WO₃-n nanosheets was 2-3 times to bulk WO₃-b,indicating the suppressed carrier recombination by porous nanosheets morphology.The EIS results confirmed the improved surface carrier transmission by the porous nanosheet morphology.3.Formation mechanism of porous rose-like WO₃ and its photoresponse and stability studyBased on the fabrication of porous WO₃ nanosheets,porous rose-like WO₃ was prepared by changing the amount of H₂C₂O₄ in CBD process.By controlling the amount of surfactant and reaction time,a series of samples were obtained and possible formation mechanism was pointed out.By constructing oxygen defects on material surface the light response region of material can be broadened,carbon composited rose-like porous C/WO₃-r exhibited a lower bandgap of 0.1 e V than carbon-free WO₃-r.Meanwhile,the photocurrent density of rose-like porous WO₃-r showed less damping than bulk WO₃-b₂,indicating its high photocorrosion resistance.The EIS results confirmed that the rose-like morphology can promote carrier transmission on the material surface.4.Synthesis of WO₃/g-C₃N₄ nanocomposites and their photocatalytic activityH₂WO₄/g-C₃N₄ composites were prepared by adding g-C₃N₄ in CBD process.After annealing,WO₃/g-C₃N₄ composite photocatalysts were obtained.The anchoring morphology and Z-scheme band structure of composite photocatalysts were confirmed by a series of characterization.A special vertical 2D/2D structure was pointed out in this work,compared with traditional paralleled 2D/2D structure it had a higher specific surface area and more surface active sites,which can make both materials effectively interact with incident light and reactant.The experimental results confirmed the weak photocatalytic decolorization ability of pure WO₃,while the photocatalytic decolorization efficiency of Rhodamine B(Rh B)and tetracycline hydrochloride(TCH)by optimal WO₃/g-C₃N₄-4 were99.65%and 86.97%,separately.The photocatalytic decolorization rate of Rh B and TCH by WO₃/g-C₃N₄-4 were 3.28 times and 3.32 times to pristine g-C₃N₄,respectively.The results confirmed the improvement of photocatalytic property by special anchoring structure and Z-scheme band structure.