Preparation Of Direct Ethanol Fuel Cell Anode Catalyst Pd Particles And Its Electrochemical Properties Investigation

With problems of energy and environmental developing, direct ethanol fuel cells because of its high rate of energy conversion, green and ethanol is easy to obtaine gradually become a research hotspot. But the high cost of anode catalyst limits the commercial application of direct ethanol fuel cell. This thesis has developed three preparation methods of direct ethanol fuel cell anode catalyst (Pd particles). During the experiments, multi-walled carbon nanotubes (MWCNTs) and the room temperature ionic liquids (RTILs) were introduced in the preparation of Pd particles. X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were used to characterize the Pd particles. Electrochemical tests were carried out by cyclic voltammeters (CV), impedance (EIS) and chronoamperometry (CA). Characterization results show that Pd nanoparticles were prepared with a relatively simple preparation method and excellent electrochemical properties were displayed.The main experiments as follows:1. For the first time, palladium nanoparticles supported on MWCNTs (multi-walled carbon nanotubes), denoted as Pd/MWCNTs, were prepared by a simple pyrolysis process of PdCl2 dissolved in room temperature ionic liquids (RTILs) of 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIBF4) rather than water. XRD, TEM and EDS were used to characterize the structure of Pd/MWCNTs, and the results showed that Pd nanoparticles with highly crystalline structure and a diameter of around 4 nm were prepared, and more importantly, except for carbon and palladium no other elements were detected. The results obtained from a pyrolysis process only containing PdCl2 and EMIBF4 testified that in our developed pyrolysis process, EMIBF4 was used not only as ligands, to form a novel complex, but also as a reducing agent, to reduce Pd2+. The electrocatalytic performance of Pd/MWCNTs-modified glassy carbon electrode towards ethanol oxidation reaction (EOR) was also probed by CV, demonstrating that it was possible to utilize the obtained Pd/MWCNTs as anode materials in fuel cell.2. Pt-Pd/MWCNTs and Pd/MWCNTs were successfully prepared by a hydrothermal synthesis in which RTILs of EMIBF4 was used as solvents. XRD and EDS analysis strongly demonstrated the formation of Pt-Pd and Pd nanoparticles on the surface of MWCNTs. TEM images not only proved the preparation of Pt-Pd and Pd nanoparticles, but also illustrated that the average particle diameter of the obtained nanoparticles is close to 4nm. CV and EIS tests showed in alkaline electrolyte, EOR could proceed on the obtained catalysts modified GC electrode, also, except for the enhanced oxidation peak current, the potential onset of EOR was greatly negatively shifted for about 200mV on the Pt-Pd/MWCNTs modified GC electrode compared with the case on the Pd/MWCNTs modified GC electrode.3. Pd/MWCNTs were prepared by simple pyrolysis of PdCl2 aqueous solution with HCl. XRD and SEM were used to characterize the Pd/MWCNTs obtained, and the results showed that the diameter of the palladium nanoparticles immobilized on the MWCNTs was close to 30 nm. EDS proved the existence of elemental Pd on the surface of the MWCNTs. The electrocatalytic performance of the Pd/MWCNTs in the EOR was probed using CV. This demonstrated that it would be possible to utilize the Pd/MWCNTs as anode material in fuel cells. The main contribution of this preliminary work is the development of a novel and simple method to prepare palladium nanoparticles on MWCNTs, which will be helpful in the preparation of Pd nanoparticles on a large scale.4. By simple cyclic voltammetry of a PdO-coated glassy carbon (GC) electrode for a few cycles with the potential swept from -1.2 to -1.0 V versus saturated calomel electrode in an alkaline solution containing ethanol, a Pd particle modified GC electrode was fabricated. It showed satisfactory catalysis toward the ethanol oxidation reaction.