Dissertation
Dissertation > Environmental science, safety science > Environmental pollution and its prevention > General issues > Environmental pollution control methods and equipment

Preparation and Application of Complex Oxide Coated Nano-electrode for the Oxidation of Pollutants

Author LiZuo
Tutor ZhaoGuoHua
School Tongji University
Course Physical and chemical
Keywords Nano-scale electrodes Composite oxide electrode Tin and antimony oxides Precious Metals Rare earth metals Electrocatalytic oxidation Sol-gel - dip method Cyclic voltammetry Organic Pollutants Electrochemical oscillations
CLC X505
Type Master's thesis
Year 2006
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The Electrochemical Oxidation degradation of organic contaminants technology superiority with a series of difficult to compare with other treatment methods, and to develop efficient electrode suitable for the treatment of environmental pollutants is a hot research at home and abroad in recent years. From the to improve electrode surface microstructure and modified species two to start the preparation of nano-scale composite oxide modified electrode in order to improve the performance and working life of the catalytic electrode electrochemical, enabling efficient catalytic degradation of environmental pollutants, for practical nano-catalytic electrode used in environmental treatment to provide a reliable basis for applied research. Titanium matrix composite oxide electrode obtained by different preparation methods with different surface microstructure SnO 2 the Sb 2 O 5 / Ti electrode, while doping substance having a good catalytic performance, one for the precious metals Pt and Pd noble metal - a non-noble metal composite oxide electrode; those for the rare earth metal of La, Ce, Eu, Sm, to give a rare earth metal - non-precious metal composite oxide electrode. SEM and XRD techniques the prepared electrode characterization results showed that the sol-gel - a dip the Prepared SnO 2 Sb 2 O 5 / Ti electrode average grain size of 20nm, with a large surface of the electrochemical activity, of SnO doped Pt and Pd 2 Sb 2 O < sub> 5 / the average grain size of the Ti electrodes respectively, 25nm and 35nm, and the rare-earth dopant of SnO 2 SB 2 O 5 / Ti electrode is the average grain size of 50nm or less, are nano-composite oxide electrode. The nano of SnO 2 Sb 2 O 5 / Ti electrode potential of the oxygen evolution in acidic, alkaline and neutral media were 2.2 V, 1.0V, 2.1V, are higher than the corresponding micron of SnO 2 Sb 2 O 5 / Ti electrode 2.1V, 0.8V 1.5V oxygen evolution potential value, especially in the neutral medium quite different. Doped with platinum, palladium precious metals, oxygen evolution potential of the electrode slightly lower in acidic and neutral media, including platinum-doped nanocomposite electrode slightly lower than doped with palladium. Doped rare earth metals in acidic and neutral media oxygen evolution potential of the electrodes with nanometer of SnO 2 the Sb 2 O 5 / Ti electrode substantially the same, while the increase in the alkaline medium. Further study also concluded that if the particle diameter of the electrode surface oxide by micron achieve nanometer composite oxide electrode, the oxidation reaction in the same medium transfer coefficient β values ??increased significantly. Doping precious metals, rare earth metals and undoped nano SnO 2 Sb 2 O 5 / Ti electrode compared to the Pt dopant and Pd nano-composite oxide electrode β values ??have increased, increased significantly from 8.11% to 10.71%, which doped the Pd nano composite oxide electrode β value greater improve. The β values ??of doping a rare earth metal oxide electrode of the nano-composite has increased, increasing significantly from 6.21% to 97.53%, the highest value of β is doped with Eu nano-composite oxide electrode. The nanometer scale SnO Sb 2 O 5 / Ti electrode strength lifetime of micron-scale electrodes greatly improved compared to the original 3 times. Further doped noble metal modified strengthening life of the electrode can be increased to 4 times; doped rare earth metal, the modification strength lifetime of the electrode can be increased to about 30 hours, the undoped nano SnO 2 Sb 2 O 5 / Ti electrode 5 times. Compared with micron-scale electrodes, nano of SnO 2 Sb 2 O 5 / Ti electrodes have a better electrocatalytic properties of small organic molecules, especially formaldehyde on the nano of SnO 2 Sb 2 O 5 / Ti electrode electrochemical oscillation observed this phenomenon reflect the nano-scale effects, when the oxide particle size of nano-scale electrode surface area is greatly increased, the surface active sites increased catalytic performance enhancements. Sb 2 O 5 / Ti electrode also found a similar phenomenon in the precious metals-doped nano SnO . Showed selective catalytic oxidation of organics small molecules in electrochemical properties of doped rare earth complex oxide electrodes, such as improved electrocatalytic properties of aniline, the electrocatalytic properties declined slightly phenol. Investigated the micron scale SnO 2 Sb 2 O 5 / Ti electrode and seven kinds of nano-composite oxide electrode for phenol, aniline, benzoic acid oxidative degradation effect, and contrast. Experimental data show that, the nano of SnO 2 Sb 2 O 5 / Ti electrode relative to the total degradation ability is the micron of SnO 2 Sb 2 O 5 / Ti electrode 5 times, dopant precious metals basically unchanged, the doped rare earth metals can be further increased by 40% to 60%. And the micron scale SnO 2 Sb 2 O 5 / Ti electrode relative comparison of phenol in the nano-SnO 2 Sb 2 O 5 / Ti electrode and rare-earth-doped the SnO 2 the Sb 2 O 5 < / sub> / Ti electrode direct electrochemical oxidation degree of, the precious metals doped SnO 2 Sb 2 O 5 / Ti the degree of oxidation of the electrode directly declined; but for the electrochemical oxidation of aniline, no significant increase of the oxidative degradation of capability of nano-scale composite oxide electrode, which may affect the activity of the electrode because of the formation of a polyaniline Nano SnO 2 Sb 2 O 5 / Ti electrode surface and the current efficiency; electrochemical oxidation reaction of benzoic acid, doped Pt oxidative degradation effect as well. This thesis is further prepared filter applied to the degradation of environmental pollutants electrochemical oxidation efficiency, practicality catalytic electrode provides a good theoretical basis. The microscopic structure of the electrode surface plays an important role in the performance of the electrode catalytic oxidation of organic pollutants, the average grain size of the surface oxide of the electrode, the strengthening of the dopant species and the electrode life and degradation properties are closely related to organics doped debris species can alter the growth of crystals of the modified layer, thus affecting the microstructure and grain size of the grains, and can improve the binding ability of the antimony tin oxide layer and the Ti substrate, improve the strength lifetime of the electrode, while the average grain size decreases the active surface of the electrode can be increased, thereby improving the oxidative degradation of the electrode capacity.

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