Probing the influence of relative humidity and temperature on the sulfonated silica ceramic carbon electrode for PEM fuel cell operation

Abstract

Operation of fuel cells under low relative humidity (RH) and high temperature is a useful way to cut-down cost and increase performance. However, the Nafion ionomer employed in the electrode of the conventional fuel cells performs poorly under low RH and temperatures above 80 °C due to dehydration. A sulfonated silica ceramic carbon electrode (SS-CCE) has been developed to replace the Nafion-based electrode (NBE) because of its hydrophilic and durable nature. Fuel cell testing and diagnostic tools like cyclic voltammetry and electrochemical impedance spectroscopy have been utilized to evaluate polarization losses of different membrane electrode assembly (MEA) configurations for various operating conditions. The configurations include the symmetric NBE MEA, symmetric SS-CCE MEA and asymmetric SS-CCE MEA. Of all the configurations, the asymmetric SS-CCE MEA showed better and stable performance from 80 ℃ to 95 °C. This indicates that the SS-CCE cathode catalyst layer promotes back diffusion of water generated at the cathode to the anode resulting in an increased performance with temperature and low relative humidity. Moreover, the SS-CCE catalyst showed better stability after an accelerated stress test.