Investigation of catalyst layer defects in catalyst-coated membrane for PEMFC application: Non-destructive method

Abstract

Summary The commercialization of polymer electrolyte membrane fuel cells has been hindered by durability problems caused by defects in the manufacturing process. We demonstrate for the first time a non‐destructive, non‐contact method that uses optical microscopy and image analysis to identify defects that may lead to failure in catalyst‐coated membranes (CCMs) of polymer electrolyte membrane fuel cells. This method is applied to 2 commercial CCMs produced by the decal transfer technique. Defects in the catalyst layer (CL) at the beginning‐of‐life (BOL) are characterized in terms of their initial size and shape, and their propagation is tracked as the CCMs are aged in a non‐reactive environment. The defected area in one of the commercial CCMs increases from approximately 2.4% of the total CL area at BOL to 10.5% by end‐of‐life (EOL). BOL defects in the CL are found to propagate faster in the CCMs stored for 2 years under atmospheric conditions compared with freshly manufactured CCMs with narrow CL defects. Image analysis of another commercial CCM shows the presence of pores with diameters between 5 and 25 μm that comprise 52% of the total pore area in the CL. Other defects such as scratches and missing/empty catalyst areas are identified and characterized, providing a framework for quality control applications. Finally, the effect of defects on fuel cell performance is characterized by measurement of the open‐circuit voltage (OCV). These experiments show that CCMs with a large number of cracks in the CL exhibit a voltage loss of 2.55 mV/hr, whereas CCMs with thin/missing/empty CL defects show a loss of 1.12 mV/hr.

The effect of ink dilution and evaporation on the microstructures of catalyst layers in polymer electrolyte membrane fuel cells

“…Similarly, if the generated heat is not removed effectively, “hot spots” will occur at the corresponding reaction sites and may cause cracks in the CLs and delamination of the CLs from their membranes, increasing contact resistance . Furthermore, an uneven current density will make temperature distribution uneven and cause various chemical degradation modes, therefore leading to a poor catalyst utilization.…”

A novel method to inspect coating thickness of tristructural isotropic fuel particles

“…Currently, ceramography is the most widely used method to investigate such microstructures . Similarly, scanning electron microscopy (SEM) analysis is also a destructive technique used widely to perform cross‐sectional analysis . In terms of nondestructive inspection, X‐ray phase‐contrast imaging (PCI) is preferred over conventional X‐ray imaging because it can image adjacent coating layers with sharp interfaces without sacrificing time in the examination of TRISO fuel particles .…”

“…5,6 Similarly, scanning electron microscopy (SEM) analysis is also a destructive technique used widely to perform cross-sectional analysis. [7][8][9] In terms of nondestructive inspection, X-ray phase-contrast imaging (PCI) is preferred over conventional X-ray imaging because it can image adjacent coating layers with sharp interfaces without sacrificing time in the examination of TRISO fuel particles. 10,11 Woong Ki Kim et al first applied PCI to visualize the structure of each coating layer, then the Sobel operator and a 3 × 3 average filter were used to extract interfaces between coating layers.…”

Geometric pore surface area and fractal dimension of catalyzed electrodes in polymer electrolyte membrane fuel cells

“…Electrode in polymer electrolyte membrane (PEM) fuel cells is a porous medium, typically composed of two distinct layers: a catalyst layer (CL) and a gas diffusion layer (GDL) . The CL is the platform where the electrochemical reactions occur, and it conventionally consists of catalyst, binding materials, and pores . The materials and structure of the CLs provide the reaction sites, proton and electron pathways, and channels for reactant supply and by‐product removal, which are essential for effective electrical energy conversion .…”

“…1,2 The CL is the platform where the electrochemical reactions occur, and it conventionally consists of catalyst, binding materials, and pores. 3,4 The materials and structure of the CLs provide the reaction sites, proton and electron pathways, and channels for reactant supply and by-product removal, which are essential for effective electrical energy conversion. [5][6][7][8] The GDL, however, is usually made of a carbon paper or cloth covered by a thin layer of carbon particles on the CL side (a.k.a.…”