The increasing requirement for renewable energy places high-temperature proton exchange membrane fuel cells (HT-PEMFCs) on the forefront of “green” energy-generating power devices. Compared to certain PEMFC technologies, HT-PEMFCs possess faster electrode kinetics, high tolerance to fuel poisons and impurities, no humidification requirements, simplified cooling and system design.¹ Herein we present optimization strategies of membrane electrode assemblies (MEAs) for HT-PEMFCs, focusing mainly on the (1) component characterization, (2) MEA fabrication, and (3) testing protocols. A selection of gas diffusion electrodes (GDEs) was tested, as well as the presence/absence of a microporous layer (MPL) on the cell performance. The catalyst layer (CL) has been modified in the terms of fabrication methods, catalyst type, platinum (Pt) content, as well as a variety of binders and additives. The PEM optimizations focused on varying and testing: (1) the molecular weight (Mw) of polybenzimidazole (PBI) for membrane casting, (2) PEM thickness, and its (3) acid doping levels (ADL). The MEAs were then fabricated at altering hot-pressing conditions and their performances were compared. The MEA testing focused on activation, humidity levels, high current operations, elevated temperature and pressure operations, as well as long-term stationary and dynamic durability protocol studies. The material fabrication optimizations resulted in higher onset and peak-of-life voltages, as well as longer cell durability. Together with optimized cell testing, we have achieved power densities of more than 0.8 W/cm², with stationary durability of more than 13,000 hours at 0.3 A/cm² current density, with the degradation rate of 4 μV/h. Originally the dynamic durability was demonstrated with more than 290 start-stop cycles showing the performance degradation of up to 100 µV/cycle, however, new tests show degradation rates of less than 46 µV/cycle. The performance and durability that we have demonstrated here position HT-PEMFCs as matured technology that can enter the mass market as a commercial and reliable electrochemical power device, to answer the ever-increasing societal energy demands in the age of climate change.

Figure 1. Performance of Blue World Technologies MEAs: (A) from different production batches showing small performance scatter, and (B) i-V and power curves at elevated pressures.

Reference:

1. O. Jensen, D. Aili, H. A. Hjuler, Q. Li, High Temperature Polymer Electrolyte Membrane Fuel Cells - Approaches, Status and Perspective, ISBN 978-3-319-17081-7; DOI 10.1007/978-3-319-17082-4, Springer International Publishing, New York, 2015.