Computational Quantum Chemistry Analysis of the Cathodic Catalyst in Low Temperature Fuel Cells

• Main Authors: Hsu, Chuan-Lin, 許湶琳
• Other Authors: 洪哲文
• Format: Others
• Language: zh-TW
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/14181425720357677039

碩士 === 國立清華大學 === 動力機械工程學系 === 102 === Enhancing the conversion efficiency from hydrogen to electricity is always the target of fuel cell research. The oxygen reduction reaction (ORR) in the cathode is regarded the rate-limited step. Platinum alloys are common methods to increase the catalyst activity. However, platinum is rare and expansive, therefore it’s the reason that fuel cell can’t be commercialized. In this research, platinum doped single wall carbon nanotube and graphene that have good electrical conductivity and high specific surface area are used as nano-frames for reducing the usage amount of platinum in cathode. It is difficult to study the whole process of ORR by experiments. Therefore, this thesis studies the mechanisms of the reaction by First Principles calculation using Density Functional Theory (DFT). The adsorption energy, total energy of the system, reaction energy and activation energy of the ORR are all evaluated. Since oxygen adsorption is the first step of the ORR, the adsorption energy and relative energy are calculated for different initial adsorption forms. It is found that Pt doped graphene can offer a stable reaction environment. However, a stable reaction environment does not promise a good reaction activity. This research uses Sabatier analysis methodology to calculate the reaction activity. In order to find out the highest reaction activity, the weight percentage of Pt doped nano-frames is tuned. It is found that the 94.2 wt% has its best reaction activity for Pt doped graphene and the 14.62 wt% has its best reaction activity for Pt doped single wall carbon nanotubes. Both of these two nano-frames can reduce the usage amount of platinum, increase the reaction area and maintain an excellent reaction activity.