Dead-ended anode polymer electrolyte fuel cell stack operation investigated using electrochemical impedance spectroscopy, off-gas analysis and thermal imaging

In situ diagnostic techniques provide a means of understanding the internal workings of fuel cells so that improved designs and operating regimes can be identified. Here, a novel metrology approach is reported that combines current and temperature mapping with water visualisation using neutron radiography.The approach enables a hydro-electro-thermal performance map to be generated that is applied to an air-cooled, open-cathode polymer electrolyte fuel cell. This type of fuel cell exhibits a particularly interesting coupled relationship between water, current and heat, as the air supply has the due role of cooling the stack as well as providing the cathode reactant feed via a single source. It is found that water predominantly accumulates under the cooling channels (thickness of 70-100 µm under the cooling channels and 5-25 µm in the active channels at 0.5 A cm KeywordsAir-cooled open-cathode polymer electrolyte fuel cell; water mapping; neutron imaging; temperature mapping; current mapping.

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“…otherwise confined to open-cathode fuel cells [23][24][25] or the outer surface of a cell or stack [26,27].…”

Section: Current and Temperature Mapping In Fuel Cellsmentioning

confidence: 99%

“…Combined temperature and current mapping studies offer an extra dimension of information and allow the impact of each parameter on the other to be assessed [15,26,19,27]; however, the other important component in this equation, water, needs to be considered in unison to see the whole picture.…”

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confidence: 99%

The Hydro-electro-thermal Performance of Air-cooled, Open-cathode Polymer Electrolyte Fuel Cells: Combined Localised Current Density, Temperature and Water Mapping

Meyer

Ashton

Jervis

et al. 2015

Electrochimica Acta

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“…In this study, two stacks are compared (Stack-A and Stack-B), with the only difference being the anode GDL ( Figure 1). The test station supplied dry hydrogen (with a purity of 99.995 %) at ambient temperature to the anodes and air was forced through the stack by a single fan (SanAce 36, Sanyo Denki, Japan) to the open-cathode channels [65]. The fan, which provides cooling and air supply to the cathode, was controlled by a programmable power supply (3649A Agilent, UK), and installed on top of an aluminium air funnel (Figure 1).…”

Section: Fuel Cell Testingmentioning

confidence: 99%

“…The operation of this fuel cell in terms of cathode design, cooling and active channels and materials, has been described in previous reports, and is summarised in Figure 1 [65,66]. The cathode is operated in flow-through mode, with an air flow rate of 1 × 10 -3 m 3 s -1 .…”

Section: Fuel Cell Testingmentioning

confidence: 99%

“…An in-house computer-controlled system controlled the air, hydrogen, cooling and electrical valves (LabVIEW, National Instruments, USA) as well as recording and presenting data using a data acquisition card (USB 6363, National Instruments, USA). Ambient temperature, pressure (absolute) and relative humidity (RH) were measured at 25 °C  0.2 C, 0.97  0.02 bar and 40 %, respectively, during all tests.The operation of this fuel cell in terms of cathode design, cooling and active channels and materials, has been described in previous reports, and is summarised in Figure 1 [65,66]. The cathode is operated in flow-through mode, with an air flow rate of 1 × 10 -3 m 3 s -1 .…”

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confidence: 99%

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Effect of gas diffusion layer properties on water distribution across air-cooled, open-cathode polymer electrolyte fuel cells: A combined ex-situ X-ray tomography and in-operando neutron imaging study

Meyer

Ashton

Boillat

et al. 2016

Electrochimica Acta

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2 Highlights First description of in-plane water distribution using neutron imaging in an aircooled, open-cathode fuel cell. High water content identified under cathode land area, whereas anode water content is relatively homogeneous. Water distribution in anode GDL directly linked to dispersion of PTFE. Anode GDL composition shown to affect water content and distribution in cathode. Combined X-ray computed tomography, SEM/EDS and TGA used to characterise GDL structure and composition. AbstractIn-situ diagnostic techniques provide a means of understanding the internal workings of fuel cells under normal operating conditions so that improved designs and operating regimes can be identified. Here, an approach is used which combines exsitu characterisation of two anode gas diffusion / microporous layers (GDL-A and GDL-B) with X-ray computed tomography and in-situ analysis using neutron imaging of operating fuel cells. The combination of TGA, SEM and X-ray computed tomography reveals that GDL-A has a thin microporous layer with 26 % PTFE covering a thick diffusion layer composed of 'spaghetti' shaped fibres. GDL-B is covered by two microporous media (29 % and 6.5 % PTFE) penetrating deep within the linear fibre network. The neutron imaging reveals two pathways for water management underneath the cooling channel, either diffusing through the cathode GDL to the active channels, or diffusing through the membrane and towards the 3 anode. Here, these two behaviours are directly affected by the anode gas diffusion PTFE content and porosity. KeywordsGas diffusion layer; air-cooled open-cathode; X-ray computed tomography; neutron imaging; water management. IntroductionPolymer electrolyte fuel cells (PEFC) fuelled with hydrogen are among the most promising energy conversion technologies for a broad range of applications, including portable, stationary and automotive power delivery. However, understanding the cell water management is crucial for performance optimisation.Flooding impedes reactant transport (water mainly concentrating at the cathode) and reduces the surface area of the catalyst, causing significant if not catastrophic decay in cell performance, and dehydration can lead to cracks and irreversible damage [1][2][3]. The gas diffusion layer (GDL) provides a pathway for electron transport, ensures even reactant delivery and helps water management within each cell. The water balance between flooding and membrane dehydration is a function of the GDL's structure, porosity and PTFE (hydrophobic) content. Here, two commercial GDLs with microporous layers are characterised ex-situ by capturing the design and structure via X-ray computed tomography (CT), along with its polytetrafluoroethylene (PTFE) / carbon distribution via SEM/EDS analysis and thermogravimetric analysis (TGA); in-situ 'visualisation' of the water distribution in the in-plane orientation was performed using neutron radiography. These techniques can be correlated with one another to gain new insights into the water management role of the GDL in fuel c...

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In Situ and Operando Characterization of Proton Exchange Membrane Fuel Cells

2019

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For proton-exchange-membrane fuel cells (PEMFCs) to become a mainstream energy source, significant improvements in their performance, durability, and efficiency are necessary. To improve their durability, there must be a solid understanding of how the structural and electrochemical processes are affected during operation to propose mitigation strategies. To this aim, in situ and operando characterization techniques locally identify structural and electrochemical processes, which cannot be captured using conventional techniques. Nevertheless, linking these properties in the same geometric area has been challenging due to its inherent limitations, such as sample size and imaging resolution. This has created a knowledge gap in structure-to-electrochemical performance relationships as operation and degradation unevenly affect different areas of the cell.

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Dead-ended anode polymer electrolyte fuel cell stack operation investigated using electrochemical impedance spectroscopy, off-gas analysis and thermal imaging

Cited by 73 publications

References 40 publications

The Hydro-electro-thermal Performance of Air-cooled, Open-cathode Polymer Electrolyte Fuel Cells: Combined Localised Current Density, Temperature and Water Mapping

The Hydro-electro-thermal Performance of Air-cooled, Open-cathode Polymer Electrolyte Fuel Cells: Combined Localised Current Density, Temperature and Water Mapping

Effect of gas diffusion layer properties on water distribution across air-cooled, open-cathode polymer electrolyte fuel cells: A combined ex-situ X-ray tomography and in-operando neutron imaging study

In Situ and Operando Characterization of Proton Exchange Membrane Fuel Cells

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