Fabrication Of Nano Semiconductor-Graphene Materials Modified Rotating Ring-Disk Electrodes And Their Application In Analysis

Rotating ring-disk electrode（RRDE） is a special kind of technique for the component analysis of intermediate products and investigation of electrode reaction mechanism, which has a very important academic significance and a strong application value in monitoring the intermediates and studying the redox of organic pollutants. In this master dissertation, different kinds of nanocomposites based on nano-semiconductors and graphene were prepared. We utilized these nanocomposites modify the rotating ring-disk electrode（RRDE） for photoelectrocatalytic analysis of organic pollutants and investigation of electrode reaction mechanism. The main contents are described as follow:1. Fabrication of Cu₂O-rGO nanocomposites modified RRDE and its application in photoelectrocatalytic analysis of hydroquinone.Reduced graphene oxide（rGO）-based Cu₂ O nanocomposites were prepared by a facile one-pot reaction process using L-ascorbic acid as the reducing agent, in which both the formation of Cu₂ O nanoparticles（NPs） and the reduction of graphene oxide（GO） were achieved. Then, the synthesized nanocomposites were characterized by transmission electron microscope（TEM）, high resolution transmission electron microscopy（HRTEM）, X-ray photoelectron spectroscopy（XPS） and X-ray powder diffraction（XRD）. The electrochemical behaviors of hydroquinone（HQ） at Cu₂O-rGO modified RRDE were systematically investigated by the hydrodynamic differential pulse voltammetry. The results showed that HQ was photoelectrocatalytic degraded to electroactive hydroxyhydroquinone at Cu₂O-rGO modified disk, which was simultaneously collected and detected at bare ring electrode due to its further oxidation signal at about +0.02 V. Under the optimal conditions, the oxidation peak current had a good linear relationship with the HQ concentration in the range from 5.0×10-6 to 1.0×10-3 M, with a low limit of detection and excellent reproducibility.2. Fabrication of MoS₂-rGO nanocomposites modified RRDE and its application in photoelectrocatalytic analysis of p-chlorophenol.Under neutral condition, molybdenum disulfide（MoS₂）-rGO nanocomposites were synthesized by a one-pot hydrothermal process using exfoliated GO solution together with Na2MoO4·2H₂O and thiourea. Then, SEM, TEM and XRD were used to characterize the morphology and composition of MoS₂-rGO nanocomposites. In this work, we have successfully fabricated the MoS₂-rGO nanocomposites modified RRDE for photoelectrocatalytic analysis of p-chlorophenol（4-CP）. 4-CP would ungergo photoelectrocatalytic degradation at MoS₂-rGO modified disk electrode to give an electroactive species, which could be detected at ring electrode. Thus, the electrode reaction mechanisms on the disk can be further analyzed via monitoring the electroactive intermediate products.3. Synthesis of CuAu-ZnO-rGO nanocomposites and its investigation in enhanced photocatalytic degradation performance.A novel rGO-based bimetallic alloy-semiconductor catalyst: CuAu-ZnO-rGO nanocomposites were synthesized through a two-step procedure involving the co-reduction in oleylamine（OLA）, and OLA served as reducing agent, coordinating ligand, capping ligand and solvent. The obtained materials were characterized by UV-vis spectrum, XRD, XPS, TEM, HRTEM, energy dispersive X-ray analysis（EDX） and EDX mapping. Due to the synergistic effect among CuAu NPs, ZnO nanopyramids and rGO sheets, CuAu-ZnO-rGO behaved an enhanced photocatalytic activity for the photocatalytic degradation of organic dyes methyl orange, methylene blue, indigotin, sunset yellow and tartrazine under the simulated sunlight irradiation.