| The application of nano-sized materials to the field of electro catalyst,the preparation of nano-sized materials with template method and the preparation of porous anodic aluminua(PAA)template were reviewed in this thesis.Based on the summary,some nano-sized materials such as metals and alloy,transition-metal ferricyanide and conductive polymer were fabricated in PAA and were characterize by Scanning electron Microscope(SEM),X-ray power diffraction(XRD),X-ray photoelectron spectroscopy(XPS)and FT-IR spectroscopy.Their electrocatalytic properties also were studied.The main contents and results are as follows:1.The PAA with a different diameter of pores were prepared.The result showed the more the purity of aluminum is high,the more the homogeneity and ordering are good.The relationship between nanohole diameter and anodizing voltage was almost linear.The Cyclic voltammo -grams of PAA indicated the H+ ion(H2O)could transit the barrier layer.2.Based on rectifying properties of PAA,an electrochemical method to remove barrier of PAA is presented firstly.The barrier of PAA was dissolved by electrolysis in a three-electrode cell with PAA as cathode in neutral potassium chloride solution.The most suitable experimental conditions for removing barrier layer are the applied potential at -1.8～2.3 V,temperature at below 15℃and electrolytic time for 7～15 min. Electro -chemical method can effectively remove barrier of PAA and doesn't enlarge the nanohole diameter.Based on this kind of template, some novel nano-sized materials modified-electrodes were prepared.3.Nano-sized Cu modified PAA electrodes are fabricated by direct currents electrodeposition.The prepared Cu wires had an average diameter of 22 nm with the cubic face-centered copper structure,highly oriented along the(111)direction.Electrochemical experiments revealed that the peak currents obtained on nano-sized Cu/PAA electrodes toward catalytic reduction of nitrite were 2 times higher than those obtained on the bulk Cu electrodes,the peak potential was 80 mV higher than that at the bulk Cu electrodes.The calibration plot is linear over the nitrite concentration range 2×10-5molL-1to 2×10-2molL-1using amperometric method.The detection limit and sensitivity were 5×10-6 molL-1and 216μA mmol-1cm-2,respectively.4.Nano-sized nickel hexacyanoferrate(NiHCF)modified PAA electrodes(Nano-sized NiHCF/PAA)are fabricated by two-step electroless dipping method.The prepared Nano-sized NiHCF had an average diameter of 25 nm.The peak currents obtained on nano-sized NiHCF/PAA electrodes toward catalytic oxidation of ascorbic acid(AA) were two times bigger than those obtained on the bulk NiHCF/Al electrodes,and the peak potential was 69 mV lower than that at the bulk NiHCF/Al electrodes.The calibration plot is linear over the AA concentration range 1×10-6to1.5×10-2mol L-1using amperometric method.The detection limit of the ampeorometric method is 2.4×10-7 molL-1.The presented method was used for determination of AA in fresh fruit and vegetable juices,and the results were consistent with those results obtained using Iodine titration method.5.A kind of nano-sized Prussian blue(PB)thin film electrode was prepared based on a two-step electroless deposition method.This kind of PB thin film electrode possessed a good electrochemical and mechanical stability,a good storage and operational stability.The modified electrode showed an excellent catalytic activity towards hydrogen peroxide reduction.The linear range of detection is found to lie between 10μM and 10 mM.The detection limit(signal to noise is 3)and sensitivity are 0.8μM and 363.5μA cm-2mM-1,respectively.6.Pt/Nano-sized Ni catalysts were prepared by direct current electrodeposition.The diameter of Pt/Nano Ni particle was about 70～80 nm.Cyclic voltammograms of Pt/Nano-sized Ni/PAA electrode exhibited the onset of electro-oxidation of methanol shifted to less anodic potential values(by 100 mV)and current enhanced up to 40 times,compared with pure Pt sheet electrode.When Pt loading amount was 42.6μg cm-2,the highest electrocatalytic activity of Pt/Nano-sized Ni /PAA could be obtained.7.Ni-Mo alloy nanowires were fabricated.The SEM micrographs revealed that the diameter of the Ni-Mo alloy nanowires was about 20～ 30 nm.Voltammetric gram of the Ni-Mo alloy codeposition presented a pronounced plateau of a limiting current.XPS indicated the potential of complete reduction of Mo ion occurs at -1.4 V,correspond -ing to the potential where plateau of limiting currents occurred.The concentration ratios of citrate salt and the ammonia salt,concentration ratios of molybdate salt and nickel salt and the electrolyte acidity had considerable effects on codeposition of Ni-Mo alloy.The as-prepared Ni-Mo alloy nanowires exhibits a better catalytic activity for hydrogen evolution reaction.8.Polyaniline nanowire thin film electrodes were fabricated by electrochemical methods.Prior to electro polymerization of aniline,a layer of metallic nickel was deposited in PAA to provide a suitable electrocatalytic layer for the electro polymerization of aniline.The PANI wires had an average diameter of 22 nm corresponding to the pore diameter of the template.The charge-discharge curves showed the charge determined for PANI nanowire/PAA is higher than for bulk PANI film grown directly on Ni/Al.Based on the present study,a new effective method has been established for fabrication and application of new nano-sized materials modified electrodes and nano-sized electrocatalyst. |
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