Effect of Membrane Electrode Assembly Bonding Technique on Fuel Cell Performance and Platinum Crystallite Size

Abstract

Major efforts are underway to reduce fuel cell manufacturing costs, thereby facilitating widespread adoption of fuel cell technology in emerging applications, such as combined heat and power and transportation. This research investigates new methods for fabricating membrane electrode assemblies (MEAs), which are at the core of fuel cell technology. A key manufacturing step in the production of fuel cell MEAs is bonding two electrodes to an ionically conductive membrane. In particular, new MEA bonding methods are examined for polybenzimidazole-based phosphoric acid (PBI/PA) fuel cells. Two new methods of bonding PBI/PA fuel cell MEAs were studied with the goal of reducing cycle time to reduce manufacturing costs. Specifically, the methods included ultrasonic bonding and thermally bonding with advance process control (APC thermal). The traditional method of thermally bonding PBI MEAs requires 30 seconds, whereas the new bonding methods reduce the cycle time to 2 and 8 seconds, respectively. Ultrasonic bonding was also shown to significantly reduce the energy consumed by the bonding process. Adverse effects of the new bonding methods on cell performance and structure were not observed. Average cell voltages at 0.2 A/cm2 for ultrasonic, APC thermal, and thermally bonded MEAs were 650 mV, 651 mV, and 641 mV, respectively. The platinum crystallite size was found to be the same before and after ultrasonic bonding using XRD. Furthermore, changes in the electrode pore structure were not observed in SEM images taken after ultrasonic bonding. The test results show that it is possible to reduce manufacturing costs by switching to faster methods of bonding PBI phosphoric acid fuel cell MEAs.