Investigation of Performance and Durability of MEAs at Higher Temperature
MEAs were manufactured using a standard Pt/Ketjen black catalyst (TEC10E50E, TKK Corp.) and Nafion. Then, their IV characteristics were examined. Regarding to the durability evaluation, two protocols recommended by Fuel Cell Commercialization of Japan (FCCJ), “load cycles” and “start-stop cycles”, were in use. Three different conditions of operation temperature and humidity (80 °C/RH100%, 105 °C/RH57%, and 80 °C/RH57%) were applied. Then, the effects of such conditions on both performance and durability of MEAs were evaluated.
On evaluation of IV performance in three different conditions before and after the load cycle durability tests, the operation at 105 °C greatly deteriorated the performance than at 80 °C. Also, by comparing two different humidity conditions at 80 °C, the lower humidity led to the smaller degradation. Moreover, the change in electrochemical surface area (ECSA) was examined at the same time, and then the retention of ECSA was lower under both higher temperature and higher humidity, likewise. In addition, SEM observations were performed to see the change in Pt particle size. As a result, Pt grain growth was confirmed after the load cycle durability tests. The average particle size became larger at both higher temperature and higher humidity. In other words, a similar trend to the deterioration of IV performance was obtained. Here, we believe that one possible reason why the deterioration was suppressed at lower humidity comes from the existence of less water relating to the diffusion of Pt ions. Similarly, the examination on the start-stop cycle durability tests will also be reported.