3D Visualisation of PEMFC Electrode Structures Using FIB Nanotomography

Zils, Susanne; Timpel, Melanie; Arlt, Tobias; Wolz, André; Manke, Ingo; Roth, Christina

doi:10.1002/fuce.201000133

Cited by 63 publications

(51 citation statements)

References 29 publications

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“…[2][3][4][5][6][7][8][9] The diamond blade used in the microtome technique has the advantage of slicing through the electrocatalyst layer without inflicting thermal damage. However, it is difficult to cut through e.g.…”

mentioning

confidence: 99%

Correlating Cathode Microstructure with PEFC Performance Using FIB-SEM and TEM

Okumura

Noda

Matsuda

et al. 2017

J. Electrochem. Soc.

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The cathode electrocatalyst layers of polymer electrolyte membrane fuel cells (PEFCs) are quantitatively investigated for different ratios of Nafion ionomer. This is achieved using focused-ion-beam coupled scanning electron microscopy (FIB-SEM) to reconstruct the three-dimensional microstructure via tomography. Parameters such as the porosity and pore size distribution were calculated from this data. The distributions of Nafion ionomer, carbon support, and platinum nanoparticles were then further clarified using transmission electron microscopy (TEM). Changes in the PEFC performance (notably the I-V characteristics, the electrochemical surface area, the activation overvoltage, and the concentration overvoltage) are thus correlated to electrode microstructure. The electrocatalyst layers of PEFCs have complicated, threedimensional (3D) porous microstructure. This microstructure plays a key role in transporting reactant gases (i.e. hydrogen and oxygen), product water vapor, charge-carrying ions, and electrons either to or from the active sites. Therefore, the overall PEFC performance is linked inextricably to the 3D microstructure of the electrocatalyst layer, and in particular to the Nafion content.1 Making quantitative correlations between the Nafion ratio, the microstructure, and the cell performance is thus essential in order to optimize the performance and efficiency of PEFCs.The microstructure of electrocatalyst layers in PEFCs is generally studied by obtaining microtome sections, or by using focused-ionbeam (FIB) techniques.2-9 The diamond blade used in the microtome technique has the advantage of slicing through the electrocatalyst layer without inflicting thermal damage. However, it is difficult to cut through e.g. individual carbon particles using this method, meaning that the resulting cross-section is typically too rough to analyze the microstructure quantitatively.2 Meanwhile, clear and well-defined cross-sections can be obtained by FIB sectioning. However, in this case there remain difficulties in quantitative observation due to thermal damage and ion damage during the sputtering process, in which the gallium ion beam generates heat locally, melting or damaging the ionomer. This can be mitigated somewhat by cooling the sample using liquid nitrogen, as described by e.g. Katayanagi et al. 2,9Electron microscopy and X-ray computed tomography (CT) are two other common methods to observe electrocatalyst layers in PEFCs. For example, Wargo et al. observed electrocatalyst layers using both nano-CT and FIB-SEM techniques, 3 whilst Litster et al. observed electrocatalyst layers using high-resolution (50 nm) nano-CT. 4 Despite CT having the distinct advantage of being a non-destructive technique, it has the disadvantage of inferior resolution compared with SEM, TEM, or scanning transmission electron microscope (STEM).Therefore, in this study we focus on sectioning samples by FIB, and performing observation using electron microscopy. FIB-SEM has already been utilized as a powerful tool to observe the microstruct...

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mentioning

confidence: 99%

Correlating Cathode Microstructure with PEFC Performance Using FIB-SEM and TEM

Okumura

Noda

Matsuda

et al. 2017

J. Electrochem. Soc.

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“…In the process, a FIB/SEM system was used to obtain the 3D structure of mesoporous samples (Joos et al, 2012;Porta et al, 2013;Siddique and Liu, 2010;Thiele et al, 2011;Wu et al, 2012;Zils et al, 2010). The process involves milling away a slice of the sample as thin as 10~15 nm from the side wall of a trench using FIB, and taking an SEM image of the new surface as illustrated in Figure 1.…”

Section: Fib/sem Imagingmentioning

confidence: 99%

“…For example, using X-ray computed tomography or focused ion beam/scanning electron microscopy (FIB/SEM), one can visualise the interior structure of the catalyst layer at resolutions from 100 nanometres to a few nanometres Zils et al, 2010). These, together with the SEM imaging technology, can unravel the catalyst layer structure and locate the distribution of the catalyst in the agglomerates .…”

Section: Introductionmentioning

confidence: 99%

Reliability of the spherical agglomerate models for catalyst layer in polymer electrolyte membrane fuel cells

Zhang

Ostadi

Jiang

et al. 2014

Electrochimica Acta

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“…There has been an increase over the past few years in use of nano-tomography to characterise CL at resolutions of a few nanometres [4,[18][19][20]29]. This makes simulation of oxygen diffusion and reduction in a real CL feasible, and can be used to directly calculate the electrochemical reaction rate without need to simplify the CL structure [30,31].…”

Section: Introductionmentioning

confidence: 99%