Understanding the role of the anode on the polarization losses in high-temperature polymer electrolyte membrane fuel cells using the distribution of relaxation times analysis

To investigate the role of the anode on the polarization losses of a High-Temperature Polymer Electrolyte Membrane Fuel Cell (HT-PEMFC), we analyzed impedance data using the Distribution of Relaxation Times (DRT) method. Thereby, we varied the operating conditions of the anode (humidification, nitrogen dilution, and carbon monoxide (CO) impurities) to study its impact on Nyquist plot and DRT spectrum. Humidification of the hydrogen was found to dilute phosphoric acid, which is visible in the DRT. Nitrogen dilution of the anode gas slightly increases the Mass Transport (MT) resistance. Furthermore, CO was added to anode gas fed and it impacts the impedance throughout the whole frequency range, specifically the medium and low-frequency range, typically assigned to ORR kinetics and oxygen MT. For a more detailed analysis of the impedance data, a reference electrode was employed to separate the overpotential caused by each electrode. The DRT spectrum of the anode exhibits only one peak at 1 kHz. In the presence of CO, a second peak arises corresponding to side-reactions occurring as the anodic half-cell potential increases. It was found that the cathode is affected by CO on the anode merely by the lowered cell potential and not by CO directly

Spectrophotometric Analysis of Phosphoric Acid Leakage in High-Temperature Phosphoric Acid-Doped Polybenzimidazole Membrane Fuel Cell Application

High-temperature proton exchange membrane fuel cells (HT-PEMFCs) utilize a phosphoric acid- (PA-) doped polybenzimidazole (PBI) membrane as a polymer electrolyte. The PA concentration in the membrane can affect fuel cell performance, as a significant amount of PA can leak from the membrane electrode assembly (MEA) by dissolution in discharged water, which is a byproduct of cell operation. Spectrophotometric analysis of PA leakage in PA-doped polybenzimidazole membrane fuel cells is described here. This spectrophotometric analysis is based on measurement of absorption of an ion pair formed by phosphomolybdic anions and the cationoid color reagent. Different color reagents were tested based on PA detection sensitivity, stability of the formed color, and accuracy with respect to the amount of PA measured. This method allows for nondestructive analysis and monitoring of PA leakage during HT-PEMFCs operation

Electrolyte loss and voltage degradation of HT-PEM fuel cells operated at 200oC.

As the world transitions toward a more sustainable energy future, it becomes clear that fuel cells will play a role in the global sustainable energy infrastructure. Of the many types of fuel cells, high temperature proton exchange membrane (PEM) fuel cells operating in the range of 120-200oC are particularly interesting as they offer several advantages over low temperature proton exchange membrane fuel cells. Most notably high temperature proton exchange membrane fuel cells exhibit increased tolerance to fuel impurities and simplified water management system requirements. These advantages are offset by a significantly shortened operational lifespan which makes high temperature proton exchange membrane cells suitable for small rugged applications including unmanned aerial vehicles, emergency backup power systems, and portable power production. The focus of this research is to extend the lifespan of high temperature membrane electrode assemblies (MEA’s) through a fundamental understanding of what the degradation modes are, what common process parameters best suit high temperature operation, and an understanding of the role of water in cell operation. The research is focused on operation at the higher reaches of the high temperature PEM range at 200oC. Initially the gap in previous literature will be identified and addressed as the exact degradation rate at our ideal operating conditions is not well understood with commercially available MEAs. Postmortem and in situ analysis of MEAs was undertaken to better understand the modes of degradation. This was followed with testing into the effective role of water on cell function and with innovative MEA design to promote cell longevity. To explore the impact of utilizing reformate fuels, a techno-economic analysis was undertaken comparing solid oxide fuel cells (SOFC) to high temperature proton exchange membrane fuel cells (HT-PEM) for use with a pyrolysis process