Direct Formic Acid Fuel Cell, A Catalyst Carrier

In the recent years, direct formic acid fuel cell (DFAFC) has received more and more attention because it has many advantages. Many efforts are on the increase in the electrocatalytic performance of the catalysts of DFAFC. The electrocatalytic performance of the catalysts is mainly related to the component, structure and support of the catalyst. This thesis mainly investigated the increase in the electrocatalytic performance of the catalysts in DFAFC from the improvement of the supports.Carbon support is the usually used support of the catalysts in fuel cell. Especially, cammercialized Vulcan XC-72 carbon black (XC) is normally used carbon support material for DFAFC. However, it has some disadvantages, such as easy tobe oxidized and poor stability. Therefore, usage of more stable carbon support is the important investigation direction. This thesis mainly investigated the electrocatalytic performances of the cathodic or anodic Ir or Pd catalysts supported on the macropore carbon (MC) and the mixture of tungsten carbide (WC) and XC.The main results obtained are as follows:(1) The Ir/MC and Ir/XC catalysts were prepared with the pre-deposited method. It was found that the electrocatalytic activity of the Ir/MC catalyst for the oxygen reduction is better than that of the Ir/XC catalyst. This could be only attributed to the large pore diameter and porosity as well as high graphitization extent of MC because the average diameters and relative crystallinity of two catalysts are similar. In addition, Both catalysts have the good formic acid tolerance ability.(2) The electrocatalytic performances of the Pd/XC and Pd/MC catalysts for the formic acid oxidation were investigated and compared. It was found that the electrocatalytic activity and stability of the Pd/MC catalyst for the oxidation of formic acid is better than that of the Pd/XC catalyst. Because the average size and relative crystallinity of the Pd particles in two catalysts are similar, the reason for the better electrocatalytic performances of the Pd/MC catalyst could be only attributed to large pore diameter and high conductivity due to the high graphitization extent of MC.(3) The electrocatalytic performances of the Pd/WC-XC catalysts for the oxidation of formic acid were investigated. It was found that the electrocatalytic performance of the Pd/WC-XC catalysts for the oxidation of formic acid is better than that of the Pd/XC catalyst. Furthermore, the electrocatalytic performance of the Pd/WC-XC catalysts is related to the mass ratio of WC and XC. When the mass ratio of WC and XC is 3:1, the electrocatalytic activity of the Pd/WC-XC catalyst is best. When the mass ratio of WC and XC is 2:1, the electrocatalytic stability of Pd/WC:XC catalyst is best.(4) The Au/XC and Au/WC-XC catalysts were prepared with the polyvinyl alcohol (PVA) protection method. It was found that the electrocatalytic activity of the Au/WC-XC catalyst for the oxygen reduction is much better than that of the Au/XC catalyst. In addition, the Au/WC-XC catalyst has the high formic acid tolerance ability. Thus, the Au/WC-XC catalyst is suitable to be used as the cathodic catalyst in DFAFC.