Abstract
Direct methanol fuel cell (DMFC) is receiving great attention worldwide in recent years due to following features: high energy density of liquid methanol (~ 4825.7 kWh/l), quick re-fueling, and simple cell design. DMFC is among the most promising type of fuel cells to be commercialized in the near future, especially for use in 3C application. However, two major obstacles of DMFC need to be overcome. Naturally, methanol crossover and low catalyst utilization. To understand the factors that affect catalyst utilization, we firstly investigated what an effective catalyst is from the operating mechanism of DMFC. Then, we analyzed the dispersion of catalyst paste, and reviewed past effects to seek the solution to improve catalyst utilization. We have hence developed a logical and simplest way to improve dispersion and subsequent catalyst utilization by using PFSI, which is one of the main components of catalyst paste, as the protecting agent instead of adding any other agent. However, it is difficult to form the steric stabilization between chemically dissimilar Pt nanoparticle and PFSI. The affinity between particle and PFSI needs to be enhanced. In this study, we have created a bonding between particles and PFSI by using silane coupling agents to improve catalyst utilization. Firstly, we identified the coupling reactions by using ESCA and NMR, and then characterized the self-assembly rate, blocking effect, dispersion, MEA performance, and catalyst utilization before and after coupling agent treatment by using EXAFS and electrochemical methods. The results indeed proved the validity of our concept and the use of coupling agent can help improve the catalyst utilization.