Degradation of Polymer Electrolyte Membrane Fuel Cell Under Pressure Cycle

Polymer electrolyte membrane fuel cell (PEMFC) is known as environmentally friendly energy sources for portable, backup power, and transportation applications. The performance and durability of PEMFC are affected by operating conditions such as the temperature, pressure, and humidification. Many studies have investigated of operating back pressure. An increase of back pressure can significant improved thermodynamics, kinetics and mass transfer in PEMFC. Wang et al. [1] studied the effect of different fuel cell operating temperatures, cathode and anode humidification temperatures, pressures and various combinations of these parameters experimentally. They found that cell performance is increased under high pressure operation due to the increase of reactant partial pressure and the exchange current density. Zhang et al. [2] carried out experiments on PEMFC at pressures of 1–3 atm. They confirmed that a low gas flow rate and a high back pressure improved the PEMFC performance using the Nafion 112 membrane at 0% RH. However, membrane electrode assemblies (MEAs) are degraded by operation of high back pressure in PEMFC. Because of the polymer chains of membrane breaks by radical attack as chemical degradation due to gas permeability. Also, mechanical degradation on MEAs occurs in many forms including cracks, pinhole and blisters by the operation of high back pressure.[3]

In this study, we examined effects of pressure cycle operation during the constant current (CC) mode on degradation of PEMFC. After pressure cycle, open circuit voltage (OCV) and current density at 0.6V were seriously decreased with increases in resistance and decreases in electrochemical active surface area (ECSA). In addition, we confirmed the pinhole in membrane, decrease in the catalyst layer thickness and interfacial separation in gas diffusion layer (GDL). Therefore, the pressure cycle generated the severe degradation in MEAs and they can the cause of early life failures.

References

[1]   Wang L, Husar A, Zhou T, Liu H., Int J Hydrogen Energy, 28 1263, (2003).

[2]   Zhang J, Tang Y, Song C, Cheng X, Zhang J, Wang H., Electrochim Acta 52, 5295 (2007).

[3]   S. Vengatesan, M.W. Fowler, X.-Z. Yuan, H. Wang, J. Power Sources 196, 5045 (2011).