2010 Volume 18 Pages 74-80
In the PEFC catalyst layer, the electron, the ion, and the gas vertically flow to the electrode plane. Therefore, the structure that the catalyst and the electrolyte ionomer and the porosity are vertically connected is preferable1. The catalyst layer based on the organic crystalline whisker in 3M company2 and the catalyst layer based on vertically aligned carbon nanotube（CNT）in the Toyota Motor Corporation3 were researched.
In this study, we propose a new fabricating process for an ideal catalyst layer structure that the material transfer paths of the ion, the gas and the electron are ensured by using the Pt catalyst support vertically aligned CNTs. The concept of the process is shown in Figure 1.
The process was examined experimentally. Vertically aligned CNTs of about 10 nm in diameter were obtained by the CVD method on the silicon substrate using published techniqe4. In order to take away the Fe compound catalyst and make bonding sites for Pt atoms, the tip of vertically aligned CNTs were burned by the heat treatment in oxygen5. In this study, the Pt catalyst was supported on the tip of vertically aligned CNT by Pt sputtering, after burning off the tip of CNT. Pt was dispersed on the tip surface of vertically aligned CNT, as shown in Figure 2. The vertically aligned CNT was coated by Nafion ionomer solution, hot-pressed with Nafion membrane, then transcribed on the Nafion membrane by peeling off the Si substrate. Figure 3 shows the cross section of ionomer coated vertically aligned CNT on the Nafion membrane.