Preparation Of Semiconductor Functionalized Graphene Nanomaterials, And Their Photoelectron Transfer, Photocatalytic Oxygen Evolution Properties

In the process of exploring the new clean energy, solar energy attracts the attentionof the scientists for its widespread and inexhaustible features. The artificialphotosynthesis, photocatalytic water splitting, used to convert solar energy intochemical energy has been considered as one of the efficient methods. In recent decades,the semiconductor-based photocatalysts have attracted the great interest of theresearchers in the field of catalyst because of its excellent photocatalytic activity andstability.In this master’s thesis, we prepared a novel hybrid consisting of manganese-basedoxide and hematite (α-Fe2O3), and used it to functionalize the reduced graphene oxide(r-GO). The characterizations in the structure and photoelectrochemical properties of thephotocatalysts were carried out, and the nanocomposites acted as photocatalyst tocatalytic oxygen evolution. The transformation of photoelectrons and the proposedmechanism of the photocatalytic water oxidation reaction were studied. The main pointswere shown as follows:(1) Mn3O4modified α-Fe2O3hybrid (α-Fe2O3/Mn3O4) was prepared withsolvothermal method, and α-Fe2O3/Mn3O4hybrid was used to functionalize reducedgraphene oxide (r-GO) with the self-assembly method. The structural characterizationsof the photocatalysts were carried out with XRD, SEM, HRTEM, Raman, FTIR andXPS, and the superior contact across the interface of α-Fe2O3, Mn3O4and r-GO wereconstructed, which promote the interfacial transfer of photoelectron. The UV-vis DRSand photoelectrochemical measurements were carried out to investigate the properties oflight absorption and photoinduced charge transfer of the photocatalyst. The resultsshown that the overpotential of the photocatalyst lowered significantly, and theperformances of light absorption and photoinduced charge separation improved as well.The excellent photocatalytic activity of the photocatalyst for the water oxidationreaction was shown under the irradiation of UV-vis light. Moreover, we investigated the photoelectrons transmission and proposed reaction mechanism of the photocatalystduring the reaction process.(2) The solvothermal method was used to synthesize the clusters of Ca2+-dopedMn3O4(Mn3-xCaxO4) and the hybrid of Mn3-xCaxO4modified α-Fe2O3(α-Fe2O3/Mn3-xCaxO4), and the nanocomposite of α-Fe2O3/Mn3-xCaxO4functionalizedr-GO was prepared by self-assembly method. The structural and morphologicalcharacterizations of the photocatalysts were carried out by XRD, SEM, TEM, Raman,XPS, and nitrogen adsorption-desorption measurement. The results of UV-vis DRS andphotoelectrochemical measurements shown that the overpotential of the photocatalystreduced significantly, and the performances of light absorption and separation ofphotoinduced charges were significantly improved. The amount of oxygen evolved bythe photocatalyst under UV-vis light was improved significantly.