Synchrotron X-ray Radiography as a Highly Precise and Accurate Method for Measuring the Spatial Distribution of Liquid Water in Operating Polymer Electrolyte Membrane Fuel Cells

Chevalier, S.; Gao, Nan; George, Michael G.; Lee, Jason K.; Banerjee, Rupak; Liu, H.; Shrestha, Pranay; Muirhead, Daniel; Hinebaugh, James; Tabuchi, Yuichiro; Kotaka, Toshikazu; Bazylak, Aimy

doi:10.1149/2.0041702jes

Cited by 48 publications

(27 citation statements)

References 53 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This attenuation coefficient was obtained through the linear regression of six experimentally measured values over a water thickness range of 0 -1.6 cm. Chevalier et al 32 provided never-before published insight into the precision of synchrotron Xray radiographic imaging of liquid water content in an operating PEM fuel cell; however, the impact of using a constant value for the attenuation coefficient on the accuracy of measuring liquid water content has not yet been reported in the literature. In previous works by Tran et al, 33,34 the attenuation coefficients of homogeneous materials (of varied thicknesses) were experimentally measured in the presence of scattered secondary photons 34 and harmonic photons.…”

Section: E3216mentioning

confidence: 99%

Considering Photon Scattering and Harmonics for Synchrotron X-ray Radiographic Imaging of Polymer Electrolyte Membrane Fuel Cells

Gao

George

Lee

et al. 2017

J. Electrochem. Soc.

View full text Add to dashboard Cite

We predicted the attenuated, undesired secondary scattered, and undesired harmonic components of measured X-ray intensities from synchrotron X-ray radiographic visualizations of liquid water in an operating polymer electrolyte membrane (PEM) fuel cell. The undesired secondary scattered component of the measured intensity increased as a function of the liquid water thickness (traversed by the X-ray beam). This increase in the secondary scattered component led to a decrease in the calibrated attenuation coefficient for liquid water, decreasing the accuracy of water quantification. We recommend calibrating the attenuated coefficient with a range of water thicknesses defined by the maximum expected water thickness present in the PEM fuel cell. The undesired harmonic component of the measured intensity also increased as a function of liquid water thickness, which led to a decrease in the accuracy of the measured liquid water thickness. Operating the polymer electrolyte membrane (PEM) fuel cell at high current densities is a strategy for achieving effective catalyst utilization and decreasing the cost of power.1 However, high current density operation corresponds to high rates of water production, and excess liquid water can lead to the inhibition of reactant transport and poor overall fuel cell performance. Therefore, effective water management is an important design objective for the PEM fuel cell.Synchrotron X-ray radiography, with its high spatial and temporal resolutions, has been used as a diagnostic tool to directly visualize liquid water transport in PEM fuel cells in operando.2-21 Radiographic images of the operating fuel cell during open circuit voltage (OCV) are termed dry-state images because we assume that excess liquid water is not present during this operating regime. For all non-zero current densities, radiographic images are termed wet-state images because of the possible appearance of additional liquid water with respect to the reference dry-state images (obtained at OCV). The cumulative liquid water thickness traversed by the X-ray beam, t w [cm], is quantified for each pixel of a collected two-dimensional (2D) wet-state image using the following relationship 22 derived from the Beer-Lambert law:where μ at [cm −1 ] is the linear attenuation coefficient for a monoenergetic X-ray beam and is a function of the photon energy, and the subscript "w" identifies the material as water. Herein, the measured intensity of the X-ray beam after traversing the sample is referred to as the attenuated intensity. I m,dr y is the measured attenuated intensity of a reference dry-state image (in the absence of liquid water), and I m,wet is the measured attenuated intensity of a wet-state image.The accuracy of liquid water thickness quantities determined from Equation 1 corresponds to the accuracies of the measured attenuated * Electrochemical Society Student Member. 23 determined that the vertical position of the incident beam oscillated with a significant amplitude of 25 μm, which resulted in image artifacts. The auth...

show abstract

Section: E3216mentioning

confidence: 99%

Considering Photon Scattering and Harmonics for Synchrotron X-ray Radiographic Imaging of Polymer Electrolyte Membrane Fuel Cells

Gao

George

Lee

et al. 2017

J. Electrochem. Soc.

View full text Add to dashboard Cite

show abstract

“…The error bars represent the measurement uncertainty with a coverage factor of 3, which corresponded to a confidence interval greater than 99%. The reader is referred to [17] for more details on the procedure to calculate measurement uncertainty. The catalyst coated membrane is omitted from this study since we are focusing on the liquid water accumulation in the GDL materials.…”

Section: Effect Of Hydrophilic Coating On Liquid Water Accumulation Imentioning

confidence: 99%

“…X-ray synchrotron radiography is a powerful tool for visualizing liquid water in the opaque fuel cell during operation, with high spatial and temporal resolution [17]- [19] Some authors have visualized liquid water in the GDL containing 137-2 hydrophilic components using methods such as neutron imaging [20] and cryo-SEM [16]. Mukundan et al [20] used neutron radiography to visualize liquid water in the GDL and showed that hydrophilic alumosilicate fibers in the MPL created wicking pathways for liquid water.…”

Section: Introductionmentioning

confidence: 99%

Hydrophilic Microporous Layer Coatings for Polymer Electrolyte Membrane Fuel Cells

Shrestha¹,

Banerjee²,

Lee³

et al. 2017

Proceedings of the 4th International Conference of Fluid Flow, Heat and Mass Transfer (FFHMT'17)

View full text Add to dashboard Cite

-Polymer electrolyte membrane (PEM) fuel cells are energy conversion devices that are promising components of a sustainable energy system. However, conventional fuel cells suffer from performance degradation at low humidification. To address poor performance under low humidity conditions, we investigate the effect of custom hydrophilic microporous layer (MPL) coatings on liquid water distributions in gas diffusion layers (GDLs), observed in operando using X-ray synchrotron radiography. The visualization was performed during low humidity operating conditions at 60°C, with inlet gas relative humidity (RH) of 50%. Hydrophilic MPLs were coated onto commercial hydrophobic GDLs, and electrical output and simultaneous liquid water measurements were measured, using a fuel cell test station and X-ray synchrotron radiography respectively. The hydrophilic materials showed lower values of membrane resistance (quantified by high frequency resistance) compared to the benchmark hydrophobic GDL. The relatively lower membrane resistance was attributed to improved membrane hydration under low humidity conditions. Correspondingly, the catalyst layer (CL)-MPL interface contained larger quantities of liquid water with the addition of the hydrophilic coating. However, excess liquid water at the cathode side of the GDL led to high oxygen mass transport losses at high current densities. Understanding gained from this study can be used to optimize wettability of the MPL to operate the fuel cell at low or no external humidification.

show abstract

“…[36][37][38][39][40][41][42][43][44][45] Synchrotron X-ray imaging is a powerful tool for visualizing and quantifying compositional and structural changes within opaque electrochemical devices with high spatial and temporal resolutions. [36][37][38][39][40][41][42][43][44][45] Synchrotron X-ray imaging is a powerful tool for visualizing and quantifying compositional and structural changes within opaque electrochemical devices with high spatial and temporal resolutions.…”

Section: Introductionmentioning

confidence: 99%

Graded Microporous Layers for Enhanced Capillary‐Driven Liquid Water Removal in Polymer Electrolyte Membrane Fuel Cells

Shrestha

Ouellette

Lee

et al. 2019

Adv Materials Inter

View full text Add to dashboard Cite

A novel microporous layer (MPL) is designed and fabricated with spatially graded poly(tetrafluoroethylene) (PTFE) to alleviate liquid water flooding in the cathode gas diffusion layer (GDL) of the polymer electrolyte membrane (PEM) fuel cell. In operando GDL liquid water distributions are examined using synchrotron X‐ray radiography and oxygen mass transport resistance via electrochemical characterizations, and it is found that the graded PTFE content in the MPL results in enhanced PEM fuel cell performance at high current densities (≥ 1.0 A cm−2). Specifically, less liquid water accumulates within the cathode GDL substrate, and the oxygen mass transport resistance is substantially lowered. This lower substrate water content is attributed to enhanced capillary‐driven removal of liquid water through the use of the graded MPL. This study demonstrates how strongly the spatial distributions of wettability and pore size of the MPL influence the performance of the PEM fuel cell.

show abstract

Synchrotron X-ray Radiography as a Highly Precise and Accurate Method for Measuring the Spatial Distribution of Liquid Water in Operating Polymer Electrolyte Membrane Fuel Cells

Cited by 48 publications

References 53 publications

Considering Photon Scattering and Harmonics for Synchrotron X-ray Radiographic Imaging of Polymer Electrolyte Membrane Fuel Cells

Considering Photon Scattering and Harmonics for Synchrotron X-ray Radiographic Imaging of Polymer Electrolyte Membrane Fuel Cells

Hydrophilic Microporous Layer Coatings for Polymer Electrolyte Membrane Fuel Cells

Graded Microporous Layers for Enhanced Capillary‐Driven Liquid Water Removal in Polymer Electrolyte Membrane Fuel Cells

Contact Info

Product

Resources

About