The Investigation And Preparation Of New Fuel Cell Electro-catalysts And Electrochemical Study At Liquid/Liquid Interface

Carbon nanotubes (CNTs) had been paid much attention as catalyst support due to the high electrochemical stability and large specific surface area. Fabrication of electro-catalysts for proton exchange membrane fuel cell with carbon nanotubes instead of carbon black as support had been investigated by many researchers and shown promising performances. In this thesis, based on the research of chemical modification and functionalization of carbon nanotubes (CNTs), synthetic methods of Pt/MWNTs, Pd/MWNTs , Pt-Ru/MWNTs, Ag/MWNTs catalyst and impact factors were studied and their electrocatalytic performances were discussed in detail.A liquid/liquid interface has been suggested as a simple model for biological membranes. Electrochemical investigation at the interface between two immiscible eleetrolyte solutions (ITIES) has received intensive study in the last decades. Considerable interest has been emerging and remarkable developments can be seen in the field of charge transfer at liquid-liquid interface. The liquid-liquid interface is the simplest and most promising model for understanding charge transfer processes in biological systems. Electron transfer at the liquid-liquid interface is fundamentally important for understanding the energy conversion and further investigation in simulated biomembrane.The main results are as follows:1. Embedding the nanotubes within siloxane by hydrophobic interaction; then the siloxane micelles were cross-linked with Si-O-Si framework by addition of hydrochloric acid. Such a structure probably originates from the formation of the micelle in which ammonium groups extrude outside. Therefore, the formation of an ion complex is required because the ion complex has strong hydrophilic property. Finally, a PtCl₆^2- monolayer was adsorbed onto the modified MWNT surface by electrostatic interaction and noble metal nanoparticles or the platinum and ruthium alloy were obtained by reduction. The structure of the resulting Pt/MWNTs, Pd/MWNTs and Pt-Ru/MWNTs were characterized by transmission electron micrograph (TEM) and X-ray diffraction (XRD). The electrocatalytic properties of the Pt/MWNTs electrode for methanol, ethanol and the Pd/MWNTs electrode for hydrazine have been investigated by cyclic voltammetry. The results of Pt-Ru/MWNTs also show better electro-catalytic activity to methanol than single Pt nanoparticles. 2. In aqueous solution, 4-aminobenzoic acid was covalently grafted on multi-walled carbon nanotubes (MWNTs) by amine cation radical formation in the electrooxidation process of the amino-containing compound. Then, silver (Ag) nanoparticles were electrocrystallized on 4-aminobenzoic acid monolayer-grafted MWNTs by a potential-step method. The structure and nature of the resulting Ag/MWNT composites were characterized by transmission electron microscopy and X-ray diffraction. The electrocatalytic properties of the Ag/MWNT electrode for hydrazine oxidation have been investigated by cyclic voltammetry, high electrocatalytic activity of the Ag/MWNT electrode can be observed. This may be attributed to the small particle size of the silver particles. The results imply that the Ag/MWNT composites have a good application potential in fuel cells.3. Free radicals generated by decomposition of benzoyl peroxide were used to obtain Phenylated multi-wall carbon nanotubes. Phenylated carbon nanotubes were sulfonylation with Chlorosulfonic acid at room temperature. The above-mentioned sulfonylation MWNTs were reduced to form Surface thiolation. On the basis of the functionalized MWNTs, Pt and Pd nanoparticles are well anchored to the nanotube surfaces by reduction. Transmission electron microscopy (TEM) and X-ray diffraction (XRD results show well dispersed nanoparticles on the MWNTs surface whose particle size is about 8 nm. The electrocatalytic properties of the Pt/MWNT electrode for oxidation of ethanol have been investigated by cyclic voltammetry (CV).4. Ferrocene, dimethylferrocene, decamethylferrocene, and 1, 4-diferrocinyl-1, 3-butadiyne were estimated systematically by conventional cyclic voltammetry (CV) measurements and thin-layer CV. In the thin layer method, the formal potentials of ferrocene and its derivatives shift negatively with the increase of concentration of supporting electrolyte in thin layer. This shift was caused by ion-pair effect between ferrocene and perchlorate ion. Effective formation constants for forming ion pairs are calculated and compared in thin-layer .The finding from this study accentuates the advantages of the thin film method over conventional methods, and permits a quantitative determination of the ion-pair effect using the thin-layer method. The redox behavior of triferrocenyl-methanol, a hydrophobic molecule with three structurally equivalent redox centers, was explored by thin-layer cyclic voltammetry (CV). The results demonstrate the feasibility of using molecules containing multiple redox centers to study the correlation between the thermodynamic driving force and electron transfer kinetics at liquid/liquid interfaces.