Study On Green Synthesis Of Modified Graphene-based Composites For Catalysis Of The Degradation Of Methylene Blue

Graphene with large surface area, unique electronic property and high chemical stabilityis an ideal catalyst carrier for anchoring a variety of metals or oxides and other activecomponents. In this thesis, the green synthesis of graphene/Mn02(RGO/MnO:), grapheneoxide/Mn304(G0/Mn304) and graphene/manganese doped TiO:(RGO/Mn-TiO:) compositeshave been studied, where the pristine GO suspension derived from the modified Hummersmethod is used as the raw material. The morphologies and structures of the obtainedcomposites have been characterized by TEM, SEM, XRD, XPS and Raman etc. Thegraphene-based materials are used as catalyst for the degradation of methylene blue (MB) toinvestigate their catalytic activity. The main contents and results are as follows:1.The manganese salts produced by the modified Hummers method are viewed as thewaste materials and otfen threw away. To solve this problem, the green synthesis ofRG0/Mn02nanocomposites is proposed using the pristine GO suspension as the precursorwith the assistance of additional KMn04followed by glucose reduction. The content of Mn02in RG0/Mn02composites can be tailored by changing the amount of supernatant liquid ofGO suspension. The catalytic activities of RG0/Mn02composites for decomposition of MBare investigated thoroughly. RGO/MnO: composite with88%Mn02shows100%discoloration of MB and nearly66%mineralization in the presence of H2O2.2.G0/Mn304hybrids have been in situ synthesized using pristine GO suspension by airoxidation in the presence of KOH. This method avoids the fussy procedures for the separationof GO from the suspension produced by the modified Hummers method, and only K2SO4asthe byproduct has been obtained. The G0/Mn304composites improve the wettability of thecatalyst in the aqueous solution and the decomposition of MB occurs at room temperaturecompared with our previous report of RG0/Mn02catalysts. The G0/Mn304compositesexhibit high catalytic efficiency when MB dye is used as the test probe. As a result,10mgcatalyst is able to completely decomposition of50mg L’^MB at25°C in the presence ofH2O2.3.A green method to synthesize RG0/Mn-Ti02composites is reported using the pristineGO suspension and Ti(S04)2as the precursors by hydrothermal method followed calcinationprocesses. Manganese salt, GO and sulfuric acid have been fully utilized with high efficiencyin the process. The light absorption rang of Ti02can be extended to visible light region by graphene modification and Mn doped, thus its spectral response can be widened. When thecontent of Mn and RGO in composite is0.6%and2.3%respectively, the composite shows thedegree of discoloration is nearly52%in180min for degradation of MB dye in visible light.