Metal Oxide Modified CNTs Electro-catalyst And Its Selective Electro-oxidation Of C-H Bond

The C-H bond is the basic functional group of organic compounds,and it can be transformed to C=O,C-OH bond through oxidation.It is an attractive research area to prepare aromatic aldehydes by selective catalytic oxidation of C-H bond in methyl group of aromatic compounds.The electro-oxidation is a kind of green and atomic economical synthesis method.But in the direct electro-oxidation process of C-H bond,the aldehyde was easy to be further oxidized to the carboxylic acid,and the electrode materials will directly affect the selectivity and yield of the oxidative products.In this paper,we focused on the metal oxide modified CNTs composite electro-catalyst and their electro-catalytic activities toward p-MT were studied.The MnO₂/CNTs electro-catalyst was prepared through a chemical deposit process by sulfuric acid-assisted,and its phase structure was characterized by X-ray diffraction?XRD?.The morphology and structure of MnO₂/CNTs composite were further characterized by scanning electron microscopy?SEM?,transmission electron microscopy?TEM?and high-resolution transmission electron microscopy?HRTEM?.The electro-catalytic activity of MnO₂/CNTs toward C-H bond in p-MT was studied by cyclic voltammetry?CV?and the constant potential electrolysis.The major oxidative product on the MnO₂/CNTs electrode in sulfuric acid-acetone electrolyte was p-methoxybenzaldehyde?p-MBA?which was detected by GC-MS and GC,and the yield of p-MBA was up to 80%when the electro-oxidation lasted 7 hours at 313K.It can been seen that MnO₂ and CNTs showed a synergistic catalytic activity.Different nanostructured manganese oxides have been synthesized by different alcohols-assisted methods.The crystalline phases and structure were characterized by XRD?TEM?BET.The main manganese oxides phase configuration was?-MnO₂ when ethanol was used as the assisted solvent and it showed the largest surface area.When methanol and isopropanol were used as assisted solvent,the main phases configuration was?-MnO₂.The electro-catalytic properties of the MnO₂/CNTs composites toward p-MT were studied by CV.The MnO₂/CNTs composites prepared through ethanol as assisted solvent showed the best electro-catalytic activity.In addition,the crystalline phases and structure of MnO₂/CNTs samples were also affected by magnetic stirring and ultrasonic mixing,but they showed mostly the same electro-catalytic properties.The electro-catalytic activity of WO₃/CNTs and Al₂O₃/CNTs composites toward C-H bond in p-MT to p-MBA were studied.The WO₃/CNTsandAl₂O₃/CNTscompositesshowedexcellent electro-catalytic properties,respectivly.