Development of low temperature fuel cell holders for Operando x-ray micro and nano computed tomography to visualize water distribution

Abstract

Synchrotron x-ray imaging techniques, like x-ray computed tomography (CT) and radiography have proven instrumental in expanding the communities knowledge of complex transport and reaction kinetics in electrochemical devices such as fuel cells and electrolyzers. This work presents the development of novel x-ray CT imaging techniques for operando visualization of water within low temperature fuel cells at spatial resolutions spanning the micro and nano scales. The design of operando sample holders, for both micro x-ray CT and nano CT experiments is described in depth, and prototypes of these sample holders were evaluated across a set of requirements, the most important of which are x-ray transmissibility, electrical conductivity and mechanical stability. Water segmentation from micro x-ray CT data was enabled by an image subtraction method, where the image without water is subtracted from the one with water. Through iterative experimentations, the operando nano CT cell was developed to optimize mechanical compression, electric conductivity and gas flow. While three-dimensional fuel cell reconstructions were shown possible, there remain challenges to overcome at typical lower energies (8 keV) due to beam damage, whereas it is not as significant for higher energies (>17.5 keV).

Pathway to Complete Energy Sector Decarbonization with Available Iridium Resources using Ultralow Loaded Water Electrolyzers

“…Radiography imaging was used to capture oxygen transport in the channels. The data was collected with the cell in-plane and through-plane configuration, using 5 ms exposure time for total time of 2 min per operating condition, refer to Kulkarni et al for the experimental arrangement . Constant current holds of 1–5 A and OCV was used to observe oxygen transport.…”

“…The HHV-based conversion efficiency was calculated by dividing the thermoneutral voltage (1.412 V) by the cell voltage. for the experimental arrangement 61 . Constant current holds of 1 A -5 A and OCV was used to observe oxygen transport.…”

Continuum Modeling of Porous Electrodes for Electrochemical Synthesis

“…Therefore, the water fraction and distribution within catalyst layers is one of the large uncertainties associated with multiphase volume-averaged macroscale models. Currently, experimental methods are still not sufficiently precise to measure the water or electrolyte content in the catalyst layer as a function of potential …”

“…Currently, experimental methods are still not sufficiently precise to measure the water or electrolyte content in the catalyst layer as a function of potential. 294 Because the liquid content in the catalyst layer cannot be measured easily, modeling is particularly useful for elucidating the impact of liquid saturation on electrochemical synthesis. Weng et al 60 were the first to simulate three water saturation states for the catalyst layer of a silver GDE for CO 2 reduction: a flooded catalyst layer, a uniformly wetted catalyst layer, and a catalyst layer that is described by a water-retention curve (Figure 25).…”

Observation of water droplets in microporous layers for polymer electrolyte fuel cells by X-ray computed nano-tomography

“…X-ray computed tomography (CT) has been used as a non-destructive observation method to visualize the liquid water distribution in PEFCs. Threedimensional (3D) visualization of the dynamic behavior of liquid water in a GDL substrate during operation was investigated using operando X-ray micro-CT (Eller & Bu ¨chi, 2014;Nagai et al, 2019;Kulkarni et al, 2020). However, there is no literature on observations of the shape of liquid water droplets within the nanosize pores of an MPL due to the limited spatial resolution of X-ray micro-CT.…”