A practical method to characterize proton exchange membrane fuel cell catalyst layer topography: Application to two coating techniques and two carbon supports

Abstract

The coating technique and the type of carbon support can strongly affect the surface topography, the homogeneity and the thickness of the catalyst layers of Proton Exchange Membrane fuel cells. These features can in turn strongly modify the local diffusion properties of the layer and the final cell performance, but literature about catalytic layers does not often address such issues. This work aims at studying the topography of proton exchange membrane fuel cell catalyst layers by means of 3D characterization methods. For that purpose, two types of slurries, made of Nafion Ⓡ and carbon black or a carbon xerogel, have been coated on a Kapton Ⓡ sheet by film-casting and by spray-coating. The surface topography of the samples was characterized by contact profilometry and 3D laser scanning microscopy. The data obtained with both methods were processed in order to obtain accurate 3D representations of the surface of the layers. Contact profilometry allows to perform measurements over the entire surface of the sample (5 cm × 5 cm). Layers obtained by film-casting turn out to be very smooth, but also thinner at the edges of the coating. For layers prepared by spray-coating, the reproducibility and the homogeneity are improved; however, the surface displays a higher roughness. With 3D laser scanning microscopy measurements, only a small part of the sample was analyzed (0.25 cm 2) with a high definition, allowing to characterize more precisely the surface topography. The comparison of both techniques has been enriched by the simulation of the profilometer tip motion at the surface of the observed 3D microscopy profile, giving insight into the observed differences. The 3D microscopy measurements proved to be more accurate, but not representative of the whole sample, especially for less homogeneous layers prepared by filmcasting.

Manufacturing catalyst-coated membranes by ultrasonic spray deposition for PEMFC: Identification of key parameters and their impact on PEMFC performance

“…8(a) blue line). Additionally, the difference in homogeneity across configurations is consistent with the results obtained by Deschamps et al [42], who compared the topography of sprayed layers obtained with 2 configurations of run paths and with an accumulation of 160 run paths at 33 mm height. It should be noted that the authors needed a large accumulation of layers to reach an average thickness of 6.3 µm with the commercial carbon XC-72R from Cabot ® .…”

“…In addition, the topology of the coatings can change depending on the spray pattern. Deschamps et al [42] tested two spraying configurations with and without spacing at the nozzle return and showed that the topology of the obtained deposited layers varies with the spraying configurations, suggesting a possible variation in PEMFC performance.…”

“…Other, less controllable variables influence the final shape or property of the coating. For example, Deschamps et al [42] showed that the roughness of the coating layer varies with the carbon samples and the thickness of the coating: the measured roughness of the deposited layer doubled when the thickness layer was doubled for a given carbon sample. After correlating the coating parameters with the thickness profile, we investigated the effect of the coating parameters on PEMFC performance.…”

Development of a double-side ordered membrane electrode assembly based on titanium nitride nanoarrays

“…However, it imposes higher requirements on the manufacturing process. 32,33 Several methods have been proposed for the preparation of MEAs, including scraping, 34 transfer printing 35 and spraying. 36 Park et al 37 demonstrated a scraping method via a pre-expanded PEM, and the results showed that the height and speed of the scraper can be adjusted according to the state of the paste, to realize the reproducibility of the scraping process.…”

Carbon xerogels combined with nanotubes as solid-phase extraction sorbent to determine metaflumizone and seven other surface and drinking water micropollutants

“…Furthermore, these materials are characterized by having high porosity and surface area, controllable pore size, and also having the possibility of being shaped as desired 22 , 23 . These attributes make CXs attractive materials for several applications, including fuel cells 24 , 25 , catalysis 26 – 28 and adsorption for both water treatment 29 , 30 or analytical chemistry 31 , 32 . Regarding water treatment by adsorption, some authors have been studying CXs for removal of specific PSs and CECs: (i) Moral-Rodriguez et al 33 studied different CXs for the adsorption of diclofenac; (ii) Álvarez et al 34 applied CXs as adsorbents for the removal of caffeine and diclofenac; and (iii) Carabineiro et al 35 studied the adsorption capacity of CXs for the antibiotic ciprofloxacin.…”