Preparation Of Sulfide Semiconductor/carboxylic Fluoropolymer Fiber Composites And Its Performance Of Photocatalytic Hydrogen Production From Water

In the paper, the main study is that the electrospun carboxylic fluoropolymer mats with nano-micro size interconnected open pore structure, high light transmission property and good photocatalytic resistance ability were performed using high pressure electrospinning process, then the carboxylic fluoropolymer electrospun fiber mats were used as carrier to prepare Sulfide semiconductor/carboxylic fluoropolymer fiber composites. The performance of photocatalytic hydrogen evolution from water was investigated under UV light or Xe lamp simulated sunlight irradiation.(1) The carboxylic fluoropolymer hexafluorobutyl acrylate-co-methacrylic acid (P(HFBA-co-MAA)) and dodecafluoroheptyl methacrylate-co-methacrylic acid (P(DFHMA-co-MAA)) were prepared by solution polymerization. The electrospinning experiments showed that the spinnability of P(DFHMA-co-MAA) and P(HFBA-co-MAA) copolymers became worse, the concentration of two copolymers solution decreased, the polarity and boiling point of solvent gradually reduced when the amount of MAA decreased; the diameter of fibers enlarged with increasing the amount of butanone in the spinning solvent; the spinnability of P(DFHMA-co-MAA) was better than that of P(HFBA-co-MAA). Using P(DFHMA-co-MAA) fibers as carrier, photocatalyst ZnS were prepared on the surface of fibers by two-step method. The XPS results showed that Zn2+ were introduced onto the surface of fibers by coordinating with the carboxyl of fluoropolymer firstly, then coordinated Zn2+ reacted with S2- provided by TAA to form ZnS. The amount and size of ZnS was larger when the proportion of MAA was higher in the copolymer. Nano dimension ZnS particles could be obtained when the proportion of MAA in the copolymer was 10 wt.%. The photodegradation and FT-IR analysis bored out that the as prepared ZnS/P(DFHMA-co-MAA) fiber composites had good stability under UV irradiation.(2) Using electrospinning process to produce P(DFHMA-co-MAA) nanofibers, whose average diameter is about 150 nm. And then the copper-doped zinc sulfide (ZnS) particles of about 200nm in size were immobilized on the surface of P(DFHMA-co-MAA) fibers through hydrothermal method. The composites were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), ultraviolet visible diffuse reflectance spectrum (UV-VIS), thermogravimetric analysis (TGA) and the experiment of light degradation resistance. UV-VIS analysis show that the absorption spectra of composites are mainly in the UV region. The experiment of photocatalytic hydrogen production from water under mercury lamp irradiation was also studied, the result show that the photocatalytic ability of copper-doped ZnS/P(DFHMA-co-MAA) fiber composites is better than that of copper-doped ZnS particle, which also boast good repeatability and great stability.(3) The carboxylic fluoropolymer fibers, which have around 100 nm in average diameter, of P(HFBA-co-MAA) and polyvinylidene fluoride (PVDF) mixtures are obtained by electrospinning. Zinc and indium ions are introduced onto the fiber surface by coordinating with carboxyls of MAA. Then, ZnIn2S4 particles of around 800 nm in average size are obtained and well loaded on the fiber surface through hydrothermal method. UV-VIS analysis show that the absorption edge of ZnIn2S4/carboxylic fluoropolymer fiber composites is at 510 nm within visible-light region. Photocatalytic hydrogen evolution from water was investigated using 350 W Xe lamp irradiation. It was found that the average rate of H2 evolution of ZnIn2S4 powders gradually decreased, while the average rate of H2 evolution of ZnIn2S4/fluoropolymer fiber composites increased from the first to the third run. The average rate of H2 evolution using the ZnIn2S4/fluoropolymer fiber composites as catalyst achieved 9.1 mL/h in the third run.(4) Firstly, the P(HFBA-co-MAA)/PVDF electrospun mats were used as the carrier to prepare ZnS-AgIn5S8/carboxylic fluoropolymer fiber composites. SEM images show that the ZnS-AgIn5S8 with the shape of flake or cluster loaded on the fiber surface. UV/VIS spectra show the composites have two strong absorption peaks. The first strong absorption peak in the UV region was probably generated by ZnS, while the second strong absorption in the visible region was probably generated by the AgIn5S8. Their performance for H2 evolution from splitting of water is investigated using Xe lamp irradiation under the same conditions. It was found that the average rate of H2 evolution using ZnS-AgIn5S8/fluoropolymer fiber composites catalyst was a little lower than that using ZnS-AgIn5S8 catalyst in the first run, but the average rate of H2 evolution based on the ZnS-AgIn5S8/fluoropolymer fiber composites was considerably higher than that of ZnS-AgIn5S8 powders in the second and third runs. In the third run, the average rate of H2 evolution using ZnS-AgIn5S8/fluoropolymer fiber composites catalyst is 1.86 times than that using ZnS-AgIn5S8 powders as catalyst, and achieve 9.6 mL every 2h.