Development and Characterization of a LT-PEFC Stack with an Extended Temperature Range up to 120 °C

Abstract

Usually, the operation temperature of a polymer electrolyte fuel cell (PEFC) stack for automotive application has its maximum at about 80 °C. The work presented here concerns the characterization of a 30-cell PEFC stack (2.5 kWel) developed at the German Aerospace Center, designed for operating temperatures up to 120 °C for a limited time. The possibility to run the stack at higher temperatures for a short time would contribute to the improvement of cooling system components with scaled-down dimensions. Those measures help to reduce the vehicle weight and thus to save fuel. In this contribution we present the current-voltage characteristic curves and the homogeneity obtained along the cells. Moreover, in order to investigate the stack behaviour at extended operating temperatures, a series of 20 temperature cycles from 90 to 120 °C were performed at galvanostatic conditions of 70 A (approx. 0.5 A·cm–2 and 1.5 kWel). The results are promising, since only a slight irreversible degradation was observed during the thermal cycling. Furthermore, the results of a 1200 hours long-term stability test are shown, including an end-of-life cyclovoltammetric characterization, performed on all 30 cells. The electrochemical analysis can help to find out possible causes of degradation due to catalyst or electrode degradation, and to determine hydrogen crossover rates, electrochemically active surface areas (EASAs) and electrical short-circuit resistances of each cell.