The Proton Exchange Membrane Fuel Cell Catalysts

In 1839, Professor Grove first proposed the concept of a fuel cell. Proton exchange membrane fuel cell (PEMFC) was designed by General Electric Company for NASA in the 1960s. At that time, it was only used as the power sources of space craft. PEMFC was blooming since 1980s, when Canadian Ballard began to develop its technology. During the past decade, with environment-protection and energy problems being taken into account, PEMFC as a clean and high effective energy has been paid attention to and developed.So far, PEMFC in civil applications is still very limit. This is because several key materials of PEMFC too expensive to civil applications. And catalyst is one of the key materials.The problem how to prepare an electro-catalyst with high activity and long lifetime is one of the key technologies for the PEMFC. The reaction activity of the catalyst can be adjusted by changing the preparing condition. In this paper, the preparation of the catalysts was studied in details on the reacting temperature, the composition of the solution, the pH value of the solution, and the post-processing, which significantly influenced the form and appearance, the loads of Pt, stability and activities of the catalysts.In addition, the catalyst carrier is not directly involved in electrochemical reaction, but it can determine the distribution of platinum and is involved in electron transfer and water transmission. Physicochemical properties of catalyst carrier (e.g. specific surface area, pore distribution, electrical conductivity, surface functional groups and hydrophilic property) directly affect the activities of the catalyst. In this paper, we chose several carbon materials with different physicochemical properties as the catalyst carriers, and investigated the effects of physicochemical properties of carbon carrier on the activities of the catalyst for proton exchange membrane fuel cell. The main research performance in present dissertation can be summarized and demonstrated as follows: 1. Colloid solution of platinum nanoparticles was prepared. The effect of reacting conditions in the relevance to the properties of platinum colloids was investigated. And the storage stability of platinum colloids was investigated. 20 wt% Pt/C catalyst was prepared by loading platinum nanoparticles on the carbon carrier under certain condition.2. The Pt/C catalysts were prepared via liquid phase reduction method, using ethylene glycol or formaldehyde as the reducing agent. The diameter of Pt particles was about 3nm. The preparation of the catalysts was studied in details on the reacting time, temperature, the pH value of the solution and the composition of the solution which significantly influenced the activities of the catalysts.3. The effect of post-processing on the morphology and activities of the catalyst was investigated. The platinum nanoparticles will come off the carrier and aggregate when eluting by ethanol or heating.4. Low-surface-area gelatin-based porous carbon bead, high-surface-area active carbon, multiwall carbon nanotube and Vulcan carbon XC-72 were chosen to prepare Pt/C catalysts. The effect of physicochemical properties of carbon materials on the morphology and activities of the catalyst was investigated. Carbon nanotube is a promising carrier for PEMFC catalyst.5. Platinum supported on carbon nanotubes with different tube diameter were prepared. Catalysts were studied by polarization curves. The effect of the tube diameter of carbon nanotubes on the activities of the catalysts was studied under different operating conditions (e.g. operating temperature, oxidant). It was find that at high temperature and air condition, carbon nanotube with its tube diameter of 10 ~ 20 nm support platinum has the best activities.6. Low platinum catalysts such as Pt-Fe/C, Pt-Co/C and Pt-Ni/C were prepared. The effect of another metal in alloy on the activities of the catalysts was studied. Non-platinum catalysts such as Pd/C were prepared. The diameter of Pd particles was 5 ~ 9 nm.