Study On The Structure And Photocatalytic Properties Of Graphene - Based Composite Structure

With the development of the society and the continuous improvement of modern industrialization, the worsening environment has already badly affected the human life. Therefore, searching for a far more efficient strategy to protect environment has become a research hotspot. Since the semiconductor catalyst first proposed, it has played a crucial role in environmental purification. So researchers more recently have explored a wide variety of semiconductor catalysts. However, there are some problems in those traditional photocatalysts, such as wide band gap (narrow range of spectrum response), quick recombination of photo-generated charge carries and reunion of small size nanoparticles, which need to be solved urgently.Graphene-related materials (e.g. Reduce graphene oxide) refer to those processed with two-dimension cellular structure of graphene, and exhibits some special properties, such as high specific surface area, superior adsorption capacity, excellent conductivity, etc. As new-emerging novel carbon material, wide attention has been attracted over various research fields. Especially for the application in catalysis, graphene can greatly improve the adsorption efficiency of the composite in the photocatalytic process, and restrain the recombination of photogenerated electron-hole pairs. Enormous efforts have been paid to combine graphene with nano-semiconductors via various methods, which will greatly promote the efficiency in catalysis field. Compared with pure nano-semiconductor, the introduced graphene in the hybrid structure contributes to overcome the above problems in the catalytic field. What’s more, graphene oxide (GO) processed with abundant oxygen-containing functional groups on the surface and edge, which facilitates the recombination of GO and nano-semiconductor, and further steadies the hybrid structure.Based on those considerations, GO, as the precursor, was applied to synthesize graphene-based hybrid composites via solvothermal/hydrothermal method. And the morphology, crystalline structure and photocatalytic performance of the hybrid composites have been characterized. The main research contents and results are listed as followed:1. The modified Hummers’method was adopted to prepare oxide graphene with flake graphite as raw material. The X-ray diffractometer (XRD), and field emission scanning electron microscopy (FESEM) and energy-dispersive spectrometer (EDS) were employed to analyze the structure and morphology of graphene. The results show that the sample has a large area with lamellar structure and folds surface, combined with a large number of oxygen functional groups; the hydrothermal reduction was conducted at high temperature, without addition of toxic reducing agent and crosslinking agent. The ideal reduced graphene oxide (rGO), provide with high specific surface area and abundant active sites benefitting for the subsequent recombination, was obtained after hydrothermal reaction at 180℃ for 4-6 hours,2. For the synthesis of hybrid SnS2/graphene, pentahydrate stannic chloride (SnCl4-5H2O), thioacetamide (TAA), and oxide graphene were adequately mixed, which then was transferred to autoclave and kept at 180℃ for 6 hours for the hydrothermal reaction. Transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) were employed for measurements. The uniform distribution of SnS2 nanoparticles decorated on graphene can be verified, and the improving optical absorptive property was determined. The further photocatalytic investigation of the hybrid structure was carried out with Rhodamine B as the simulative pollution. Compared with pure SnS2 or graphene, the hybrid structure provides superior photocatalytic activity and stability.3. Similar with the above SnS2, the preparation of SnO2/rGO was realized via a simple one-pot hydrothermal method, in which the SnO2 quantum dots (about 3-5nm) with visible light photocatalytic activity was successfully intersperse overall graphene surface. Transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) were also conducted. The visible light catalytic performance of the as-prepared SnO2/graphene was estimated via the similar measurements. Impressively, the hybrid nano-structure presents the more excellent visible light catalytic performance, compared with pure SnO2 and graphene. Meanwhile, the mechanism of visible light photocatalytic property and the growth mechanism of the as-prepared SnO2/graphene hybrid nano-structure were proposed.