Chapter 4 - The Effects of Temperature on PEM Fuel Cell Kinetics and Performance

Abstract

Temperature is one the most important operating conditions of PEM fuel cells, and it can significantly influence cell performance. Generally, an increase in the temperature can improve performance. In light of this fact, high-temperature PEM (HT-PEM) fuel cells operated above 95 °C (usually 95–200 °C) have recently been developed. This performance improvement at higher temperatures is mainly due to increased membrane proton conductivity, enhanced electrode kinetics for the oxygen reduction reaction (ORR) and the hydrogen oxidation reaction (HOR), and improved mass transfer of the reactants. In addition, increasing the temperature can also increase the tolerance of electrocatalysts to contaminants. However, higher operating temperatures can lead to membrane dehydration, increased hydrogen crossover rate, and the degradation of components such as electrocatalysts, gasket materials, and bipolar plates, resulting in a shortened fuel cell lifetime. Chapter 10 presents a detailed discussion of HT-PEM fuel cells. This chapter will focus on conventional (i.e. low-temperature) PEM fuel cells that use perfluorosulfonic acid membranes (e.g. Nafion ® membranes) and are usually operated below 95 °C (typically from room temperature to 80 °C). In general, fuel cell performance can be affected by several operating conditions, such as temperature, pressure, and relative humidity (RH). We will discuss the effects of RH and pressure in Chapters 8 and 9, respectively. In this chapter, only the temperature effects on the performance of PEM fuel cells will be discussed in detail.