Optimization Strategies for Commercialization of High-Temperature Pemfcs

Abstract

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. Figure 1