Study On The Photocatalytic Oxidation Performance And Electrochemical Performance Of Polyaniline-based Nanocomposites

Aiming at the problems such as large energy consumption of olefin catalytic oxidation and the poor cycling stability of polyaniline in supercapacitors,halloysite nanotubes/PANI/TiO₂composite materials and etched halloysite nanotubes/PANI/MnO₂ electrode materials were synthesized in combination of the ecomonical/resource advantages of halloysite nanotubes,the characteristics of Pickering emulsion,the low-temperature synthesis technique of TiO₂,the visible light absorption/adjustable polarity properties and high theoretical specific capacitance of polyaniline,and the specific properties of MnO₂.And their olefin photocatalytic oxidation properties and electrochemical properties were studied accordingly.The main conclusions were as follows:1.A method was developed to prepare halloysite nanotubes/PANI/TiO₂composites composed of different crystalline TiO₂ and redox state of polyaniline by low temperature in-situ polymerization with halloysite nanotubes as support and by simply adjusting the doped acid type and p H of the reaction system.The acidity of the reaction system was regulated by HNO₃,HCl,H₂SO₄ and H₃PO₄.When the p H value was 0.5,emeraldine polyaniline and anatase/rutile mixed crystal TiO₂ were obtained;while when the p H value is 1.5,the quinone dominated polyaniline and anatase TiO₂ are obtained.When the composite material was prepared with H₂SO₄ as doping acid under a p H of 0.5,the supported TiO₂ was anatase/rutile mixed crystal structure with a different surface morphology.2.The prepared halloysite nanotube/PANI/TiO₂ composite material was used as solid emulsifier to fabricate Pickering emulsion catalytic system.The average droplet size of Pickering emulsion prepared by the composite materials with different doped acids and p H values was different.When HTP/0.5/1%-HCl was used as solid emulsifier,minimum average droplet size was obtained(13.22?m).Firstly,the optimal catalyst was selected by photocatalytic oxidation of cyclohexene,and then the optimal reaction conditions for 1,1-diphenylethylene,2,3-dimethyl-2-butene and 1-methyl-1-cyclohexene photocatalytic oxidation were investigated with the optimal catalyst.The results showed that HTP/0.5/1%-HCl was the optimal catalyst,and the optimal reaction conditions for the three olefins were 10 mg catalyst,0.6 m L olefin,1.25 m L H₂O₂,solvent-free Pickering emulsion system and xenon lamp irradiation for 48 h.Under the optimum reaction conditions,1,1-diphenylethylene conversion and diphenylketone(the main product)selectivity were 97.23%and 74.68%,respectively.After four cycles,1,1-diphenylethylene conversion was 85.38%and diphenylketone selectivity was76.17%.In the photocatalytic oxidation of 2,3-dimethyl-2-butene,2,3-dimethyl-2-butene conversion and 2,3-dimethyl-2,3-butanediol selectivity(main product)were 99.16%and77.06%,respectively.After four cycles,2,3-dimethyl-2-butene conversion remained at 98.60%and 2,3-dimethyl-2,3-butanediol selectivity was 63.55%.In the photocatalytic oxidation of 1-methyl-1-cyclohexene,1-methyl-1-cyclohexene conversion and 1-methyl-1,2-cyclohexanediol selectivity were 98.34%and 55.25%,respectively.After four cycles,1-methyl-1-cyclohexene conversion was 83%and 1-methyl-1,2-cyclohexanediol selectivity was 61%.And photocatalytic oxidation mechanism for the three alkenes was proposed.3.Halloysite nanotubes/PANI/MnO₂ composite nanomaterials with different MnO₂content were prepared by in-situ aniline polymerization and KMn O₄ adsorption-reduction with etched halloysite nanotubes as carrier.The composite nanomaterials were characterized by XPS,XRD,FT-IR and EDX.It was proved that MnO₂ and PANI were successfully supported on the etched halloysite nanotubes,polyaniline doping degree in e HA/PANI/MnO₂-2.5 was 49.04%,and Mn ion valence state was mainly tetravalent.The electrochemical performance of e HA/PANI/MnO₂ composite was tested by cyclic voltammetry and galvanostatic charging-discharge method in a three-electrode system with electrochemical workstation.The result showed that the etched halloysite nanotube/PANI/MnO₂ composite nanomaterial had a higher specific capacitance,and the highest specific capacitance was obtained(768.38 F·g^-1 at the current density of 1 A·g^-1)when the feeding amount of KMn O₄ was 2.5 g.The e HA/PANI/MnO₂ composite material prepared is a supercapacitor material with enormous potential application value and is expected to be used in green energy storage equipment.