Pore Structural Characterization of Fuel Cell Layers Using Integrated Mercury Porosimetry and Computerized X-ray Tomography

Abstract

The pore structure of the cathode catalyst layer of proton-exchange membrane (PEM) fuel cells is a major factor influencing cell performance. The nanostructure of the catalyst layer has been probed, using a novel combination of mercury porosimetry with computerised X-ray tomography (CXT), even though the nanopores were below the nominal CXT resolution. The method allows probing of the macroscopic spatial variability in the accessibility of the nanostructure. In particular, mercury entrapment within the catalyst layer showed a pronounced regular spatial patterning corresponding to the already higher X-ray absorbing regions of the fresh catalyst layer. The initial, greater X-ray absorption was due to a higher local concentration of carbon-supported platinum catalyst. This was due to segregation of ionomer away from these areas, caused by the particular screen printing catalyst layer deposition method used, which both enhanced the accessibility of the origin regions and, concomitantly, reduced the accessibility of the destination regions.

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

“…Atomic Force Microscopy can also be used to measure the roughness of the surface [38]. X-ray microtomography [38,39] allows to reconstruct the 3D morphology of a catalyst layer; however the resolution as described in the two cited references allows only to visualize cracks and the largest pores (~5 µm). Paradoxically, PEMFC catalyst layer characterization by profilometry measurements are much less frequent, probably because this technique requires to produce coatings on very flat model surfaces.…”

Comparison of the impact of moisture on methane adsorption and nanoporosity for over mature shales and their kerogens

“…The intrusion of mercury was recorded 233 from 0-4137 bar. The volume of mercury entering the shale pores at a given pressure can be 234 converted to pore volume and size using the Washburn equation for slit/angular shaped pores.235A contact angle of 151.5° and a surface tension of 475.5 mN/m for mercury intrusion in shale 236 was used to provide a pore size distribution from 231 μm to 2 nm(Wang et al, 2016).237Correction methods were applied by running a blank penetrometer to remove any intrusion 238 detected from an empty penetrometer(Malik et al, 2016).…”

Two-Phase Dynamics and Hysteresis in the PEM Fuel Cell Catalyst Layer with the Lattice-Boltzmann Method

“…Examples of these insufficient methods include using stochastic geometries or methods that cannot account for the density ratio. As such, we will be looking at hysteresis, which not only is difficult to see in continuum models as well as experimentally, 43,68,96,97,103 but also is critical to examining flooding in PEMFC electrodes. 5,6 As noted previously, the way we model hysteresis is to simulate MIP with different capillary pressures in the x direction.…”

“…As such, experimental literature values vary wildly for many of the CCL, with variations by three to four orders of magnitude. [65][66][67][68][94][95][96][97] This was why this is ideally used as the test case for LBM, as we can run the simulation through a bed of packed spheres to analytically and visually describe the filling of the spherical geometry. Here, a 90 × 90 × 90 voxel geometry of spheres with a void fraction of 0.3004 was filled via the infinite film with varying capillary pressures.…”