Effects of Deep Temperature Cycling on Nafion® 112 Membranes and Membrane Electrode Assemblies

Abstract

A study was conducted to understand the physical and chemical changes in fuel cell membranes that result from Freeze/Thaw (F/T) cycling which might occur in electric vehicles. Nafion™ membranes and membrane electrode assemblies (MEA) were subjected to 385 temperature cycles between +80 °C and –40 °C over a period of three months to examine the effects on key properties. These studies were done on both compressed and uncompressed materials in the un‐humidified state. Although no catastrophic failures were seen, the analytical results shed some light on the relationship of temperature cycling to membrane structure, water management, ionic conductivity, gas permeability and mechanical strength. Changes in water swelling behavior and dry densities were noted and the effect on ionic conductivity and cell performance was examined. The impact on catalyst activity and structural integrity of MEAs was evaluated electrochemically.

A review of polymer electrolyte membrane fuel cell durability test protocols

“…Numerous experiments have tackled membrane degradation [82][83][84][85][86][87][88], examining various stressors: temperature, humidity, freeze-thaw cycling, OCV, and Fenton's test. Some examples of membrane ASTs, as well as their testing protocols, are listed in Table 7.…”

Reversible performance loss induced by sequential failed cold start of PEM fuel cells

“…As a matter of course, the freeze degradation of the key materials and components should be concerned under the subzero storage scenario. Although Nafion Ò membrane itself shows no catastrophic damage at the experimental condition of either almost dry state for hundreds of F/T cycles [23] or fully hydrated state for several F/T cycles [1], the most pronounced effect seems from others such as the physical prick from the ice in the catalyst layer (CL) [9]. Also, water redistribution in the membrane or draining out of the membrane during the cooling process was observed and could decrease the membrane degradation [9,19].…”

Aspects of fatigue failure mechanisms in polymer fuel cell membranes

“…[29][30][31] If this observation holds for other sulfonated ionomers, it follows that an ionomer cycled at high humidities could undergo less crazing since the higher humidity corresponds to higher ''filler content.'' Even though durability of polymer mem branes in fuel cell applications have received significant attention, 4,6,7,12,19,32 there is no in-depth investigation of crack formation and/or propagation based on any specific failure criteria. Ex situ characterization of the fracture behav ior of PFSA membranes has been reported in a series of pub lications by Dillard and coworkers.…”