Exploring the Impact of Cathode Ionomer Content on Alkaline Exchange Membrane Fuel Cells (AEMFCs) Using Inkjet Printing Technique
Authors: Liu Jiafei , Secanell Marc 
Published: December 2024

Hydrogen proton exchange membrane fuel cells (PEMFCs) typically rely on expensive platinum group metals (PGMs) as catalysts. A promising strategy to eliminate the need for PGM catalysts is to operate the cell under alkaline conditions. Non-PGM based AEMFCs have achieved power densities exceeding 1 W/cm2, and various commercial electrolytes, such as Tokuyama A201/A901/AS-4, FumaTech Fumasep, Ionomr Aemion, and Versogen PiperION, have been developed and are available for researchers to explore and enhance AEMFC performance. Unfortunately, AEMFCs using commercial materials have not yet demonstrated performance and stability comparable to PEMFCs even though their ion transport properties are similar. Therefore, there is a need to study the physical processes that are limiting the performance of these materials in AEMFC membrane electrode assemblies (MEAs).

AEMFCs electrode performance is very sensitive to a myriad of factors with two key factors being: a) the fabrication method; and b) ionomer to catalyst ratio. Regarding the former, unlike in PEMFCs, the number of fabrication techniques studied to fabricate AEMFC electrodes in the literature has been limited with only a handful of studies utilizing techniques such as ultrasonic spray-coating and doctor blade to control the catalyst layer structure. The development of novel fabrication techniques would therefore help the development of these technologies and allow more systematic studies to be performed, such as a detailed analysis of the ionomer to catalyst ratio. Even though previous research already showed the sensitivity of AEMFC performance to variations in ionomer content [2,4-6,11,17], its influence at varying temperatures and with newly developed commercial materials has not been thoroughly investigated. Furthermore, its effect on cell stability has not received sufficient attention.

In this work, inkjet printing is introduced as a novel fabrication method for AEMFC electrode fabrication and applied to fabricate low-loading PGM-based CCMs with varying and graded cathode ionomer loading for AEMFCs. The inkjet-printed CCMs were tested in operating AEMFCs with H2/O2 at 60 °C, demonstrating a cell power density of 0.53 W/cm2 with a total loading of 0.3 mgPt/cm2, one of the highest reported in the literature using commercial materials (see figure), along with high repeatability and stability. The effect of cathode ionomer content and grading was studied at 60 °C and 80 °C with 90% RH inlet gases. The optimal cathode ionomer content at the beginning of life was identified as 20 wt% under both conditions, but the cell experienced unstable performance over time at 80 °C, with a decrease in cell voltage during constant current holds. Adding more ionomer to the cathode decreased the rate of cell degradation, which we hypothesize is due to increased water retention. The graded cathode, with more ionomer close to the AEM, appears to be the best strategy to minimize the observed instability.

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Figure 1