Establishment Of Electrode/Microemulsion System And Studies On Related Electrochemical Reactions

Microemulsions, with special microstructures, are thermodynamically stable homogeneous systems. By using self-assembly molecules in microemulsion as a template, nano-materials with various structure and morphology can be obtained from microemulsion. Electrochemical technique as an effective synthesis and analysis approach has attracted much attention in many fields including energy transform, biology, metallurgy and corrosion science etc. Traditionally, aqueous solution, organic solution and molten salts are used as electrolyte for electrochemical reaction. Reverse microemulsion that is characterized by low conductivity is not used as an electrolyte yet. Researches show that electrochemical reactions can happen on the interface of metal/microemulsion, which are completely new electrochemical processes. In this paper, electrode/microemulsion systems were established and studies on related electrochemical reactions were carried on. The main progresses are presented as follows:1. In this text, a water insoluble IL, 1-butyl-3-methylimidazolium hexafluorophosphate([BMIM]PF6) was used to replace the organic reagent in reverse microemulsion and three styles IL microemulsions, IL/W (IL in water), WIL(bicontinuous), WIL(water in IL), were prepared by [BMIM]PF6/Triton X-100/water solution. Potassium ferrocyanide K4Fe(CN)6 was added in as a water-soluble electroactive probe, and its electrochemical behaviors at Pt/IL microemulsion interfaces were investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The experimental results show that the IL microemulsions have wider potential windows compared with conventional water solution and the W/IL microemulsion is more suitful applied in electrochemical studies. The results of CV and EIS studies indicate that in IL/W microemulsion system, the redox process of K4Fe(CN)6 / K3Fe(CN)6 is controlled by diffusion process, which is similar to that in aqueous solution. But in WIL and W/IL microemulsions, the diffusion and the charge transfer are both the controlling process. These results may be due to the unique liquid structure of the W/O microemulsion and the unique mass transfer in the WIL and W/IL microemulsion.2. In this paper, the PANI nanofibres films were successfully prepared from the glass carbon(GC) electrode/reverse microemulsion system using the reverse microemulsion composed of Triton X-100, n-hexanol, n-hexane and acidic solurion containing aniline. The CV results show that the solubility balance of aniline in W/O microemulsion can reach rapidly and the electro-polymerization behavior of aniline is different from that in aqueous solution remarkably. With the increase of scan cycle, the redox potentials difference increases gradually. Furthermore, H+ apparent concentration affects the aniline polymerization evidently. When H+ concentration is lower than 0.08 M, the electro-polymerization of aniline is difficult. With the increase of H+ concentration, the polymerization current of aniline gradually increases. When H+ concentration is high enough (0.5 M), the electro-polymerization of aniline can proceed easily. The scanning electron microscopy image shows that the deposited PANI has uniform fiber morphology with diameter of about 100 nm.3. Pd nano-particles were prepared by ultrasonic reduction method, where Triton X -100 was used as both of stiblizer and reductant. Triton X -100 containing Pd/PdCl2 was used as surfactant to prepare reverse microemulsion with n-hexanol, n-hexane and acidic solution containing HAuCl4 or NiSO4. Ni-Pd and Au-Pd composite deposits were prepared using galvanostatic method under magnetic stirring. Electrochemical properties of the composite platings were detected by CV method. The CV results show that, when PdCl2 was reduced for 60 min, Au-Pd plating has the best catalytic activity for glycerine oxidation. For Ni-Pd plating, when the reduction time is 30 min, the plating has a good electrocatalytic activity. Compared with Pd plating, both of Ni-Pd and Au-Pd platings have better electrocatalytic activity. Pd nanoparticles prepared in W/O microemulsion have smaller size, higher specific surface area and higher activity, so the obtained Ni-Pd and Au-Pd platings have much better electrocatalytic activity, which presents the advantages of W/O microemulsion for preparing nanoparticles.