Simulation of Patterned Cathode Catalyst Layer-Electrolyte Interface, with Gaussian Roughness, for Improved PEMFC Power Performance
Authors: Eardley Sam Richard , Andrews James , Du Shangfeng 
Published: May 2020

Proton Exchange Membrane fuel cells (PEMFCs) are becoming an increasingly promising piece of power generation technology that can fit into the changing economy as we strive towards a sustainable energy based future. However, PEMFCs struggle to meet the energy demands of the world, falling short of the capability of other energy sources such as fossil fuels, mainly due to price and energy output compared to the already establish combustion engines. Looking internally into the PEMFC itself, one of the main issues is the limitations of the electrode-membrane interface leading to low ion transfer performance from the catalyst layer to the polymer electrolyte membrane. If we can improve the cathode-membrane interface facilitating the oxygen reduction reaction (ORR) rate at the cathode, the rate limiting step, we can increase the overall performance of the fuel cell.

It is believed that by increasing the interfacial area of the cathode catalyst layer-membrane interface, by applying a prismatic pattern to the morphology, we can thus increase the active surface area for the membrane electrode assembly (MEA). By varying the frequency of prisms, and the relative height of these prisms compared to the fixed total height of the catalyst layer and membrane, the interfacial area can be increased, improving the current density, which would result in an improved overall power performance of the PEMFC.

In this work, with a LiveLink connection between Matlab and multiphysics software COMSOL, we model the electrode-membrane interface to investigate the influence of the operating conditions and the morphology of the membrane surface on the ion-transfer performance of PEMFCs. By varying the number and size of prism peaks applied to the interface, it is shown that we can influence the fuel cell performance whilst maintaining a constant membrane and cathode volume as well as the amount of platinum used in the catalyst layer whilst, due to economies of scale, maintaining a similar cost per membrane compared to a flat membrane interface.

Previous research has shown that there is a negative impact on power performance when the cathode catalyst layer-electrolyte interface is patterned with a low number of peaks with small relative heights compared to the total height of the electrolyte and catalyst layer. However, at higher frequencies of peaks and relative peak heights, an improvement of up to 25% was achieved in the power performance, and a 21% improvement was seen in the polarization curve.

However, this model suggests perfectly smooth interfaces between the electrolyte and the catalyst layer. In reality, there would be a level of roughness to this interface, which would have an impact on the results of the simulated fuel cell performance.

This research looks into how the application of the roughness to the interface, created using a combination of Gaussian and Uniform wave functions, will impact any previous results observed, and allow us to simulate a model that fits better with the real world findings.

The results obtained here could help determine the appropriate parameters required to validify our experimental work, and provide reference for the future work carried out in this research field.

Figure 1