Mapping Platinum Species in Polymer Electrolyte Fuel Cells by Spatially Resolved XAFS Techniques

Takao, Shinobu; Sekizawa, Oki; Nagamatsu, Shin‐ichi; Kaneko, Takuma; Yamamoto, Takashi; Samjeské, Gabor; Higashi, Kõtarõ; Nagasawa, Kensaku; Tsuji, Takuya; Suzuki, Motohiro; Kawamura, N.; Mizumaki, Masaichiro; Uruga, Tomoya; Iwasawa, Yasuhiro

doi:10.1002/anie.201408845

Cited by 43 publications

(51 citation statements)

References 49 publications

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“…(A) Scanning photoelectron microscopy (SPEM) images of a membrane electrode assembly (MEA) measured at 72 eV (Pt 4f) and 284 eV (C 1s) . (B) 2D‐mappings of Pt concentration and valence state in an MEA cathode catalyst layer derived by the Pt L III ‐edge scanning nano‐XAFS technique . (C) 3D‐light‐element distribution in the MEA cathode catalyst layer derived by X‐ray ptycho‐tomography technique …”

Section: Introductionmentioning

confidence: 99%

Operando XAFS Imaging of Distribution of Pt Cathode Catalysts in PEFC MEA

Matsui

Maejima

Ishiguro

et al. 2018

The Chemical Record

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Three‐dimensional imaging using X‐ray as a probe is state‐of‐the‐art for the characterization of heterogeneous materials. In addition to simple imaging of sample morphology, imaging of elemental distribution and chemical states provides advanced maps of key structural parameters of functional materials. The combination of X‐ray absorption fine structure (XAFS) spectroscopy and three‐dimensional imaging such as computed tomography (CT) can visualize the three‐dimensional distribution of target elements, their valence states, and local structures in a non‐destructive manner. In this personal account, our recent results on the three‐dimensional XAFS imaging for Pt cathode catalysts in the membrane electrode assembly (MEA) of polymer electrolyte fuel cell (PEFC) are introduced. The distribution and chemical states of Pt cathode catalysts in MEAs remarkably change under PEFC operating conditions, and the 3D XAFS imaging revealed essential events in PEFC MEAs.

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Section: Introductionmentioning

confidence: 99%

Operando XAFS Imaging of Distribution of Pt Cathode Catalysts in PEFC MEA

Matsui

Maejima

Ishiguro

et al. 2018

The Chemical Record

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“…[6] Recently,t here have been remarkable developments in X-ray imaging techniques [7] and XAFS imaging is promising for revealing non-uniform behavior in practical materials. [8] We previously reported the spatial distribution of Ce oxidation states in individual particles of Pt/CZ catalysts by spatially resolved scanning nano-XAFS. [9] Ex situ nano-XAFS analysis revealed differences in Ce oxidation states in individual Pt/CZ particles with different oxygen contents.…”

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confidence: 99%

Imaging of Oxygen Diffusion in Individual Platinum/Ce₂Zr₂O_x Catalyst Particles During Oxygen Storage and Release

et al. 2016

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The spatial distribution of Ce 3+ and Ce 4+ in each particle of Ce 2 Zr 2 O x in athree-wayconversion catalyst system was successfully imaged during an oxygen storage/release cycle by scanning X-ray absorption fine structure (XAFS) using hardX-raynanobeams.For the first time,nano-XAFS imaging visualizeda nd identified the modes of non-uniform oxygen diffusion from the interface of Pt catalyst and Ce 2 Zr 2 O x support and the active parts in individual catalyst particles.Heterogeneous solid catalysts are utilized for various chemical processes and are intrinsically non-uniform with respect to structure.S olid catalysts are typically in powder form, which is an assembly of non-uniform particles with different structural components (morphology,s urface structure,d omain boundary,o xygen content, and so forth). [1] In practice,the reactivity of asolid catalyst is evaluated based on the average of these structural components,and as aresult it remains difficult to understand the real variation of the active parts in ah eterogeneous catalyst. To solve this problem, spatially resolved imaging of chemical states in an individual catalyst particle is highly sought to reveal the active parts and non-uniform reaction modes at the nanoscale.Ce is ak ey element for the oxygen storage/release function in at hree-way catalyst system for clean-up of gaseous automobile exhaust;aredox process between Ce 3+ and Ce 4+ controls oxygen content in these catalyst systems. [2] However,itiswell-known that only Ce species with extensive surface defects can contribute to the redox process in pure ceria, which offers insufficient oxygen storage/release capacity.C e 2 Zr 2 O x (CZ; x = 7-8) solid-solution crystal contains an ordered arrangement of Ce and Zr atoms and exhibits excellent oxygen storage/release properties. [3] Almost 90 %ofthe Ce atoms in CZ bulk can participate in the redox

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“…Spatially resolved X-ray fine structure (XAFS) maps were collected with a dedicated nano-XAFS microscope (up to 228 225 nm 2 in resolution). [66] The as-collected 2D maps (example in Figure 8) evidenced the presence of Pt oxidized species in specific areas of the CL, namely in the zone close to the membrane/CL interface (~3 mm of distance from the interface) and in micro-cracks larger than 2 mm. In these locations it was observed not only a reduction in Pt loading, in agreement with a pronounced dissolution in proximity to the membrane observed via conventional TEM investigations, [65a] but also an increase in Pt valence and in Pt-O coordination numbers.…”

Section: Imaging the Catalyst Degradationmentioning

confidence: 95%

Experimental Methodologies to Understand Degradation of Nanostructured Electrocatalysts for PEM Fuel Cells: Advances and Opportunities

et al. 2016

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The development and application of advanced experimental tools is a major driving force in modern electrocatalysis. This is particularly true for stability studies with nanostructured oxygen reduction reaction electrocatalysts for PEM fuel cells. Indeed, our understanding of the catalyst degradation mechanisms could not have been achieved without the arsenal of analytical tools developed over the last decades. This contribution aims at highlighting the value of such a multi-faceted analytical toolbox. Several classes are examined: from techniques applied for dissolution studies with bulk electrodes, to ex situ and in situ investigations with model high-surface-area catalysts. Finally, electrochemical and imaging methods employed to characterize catalyst layers are presented. The respective features, advantages, problems and possible future developments are discussed

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Mapping Platinum Species in Polymer Electrolyte Fuel Cells by Spatially Resolved XAFS Techniques

Cited by 43 publications

References 49 publications

Operando XAFS Imaging of Distribution of Pt Cathode Catalysts in PEFC MEA

Operando XAFS Imaging of Distribution of Pt Cathode Catalysts in PEFC MEA

Imaging of Oxygen Diffusion in Individual Platinum/Ce₂Zr₂O_x Catalyst Particles During Oxygen Storage and Release

Experimental Methodologies to Understand Degradation of Nanostructured Electrocatalysts for PEM Fuel Cells: Advances and Opportunities

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Mapping Platinum Species in Polymer Electrolyte Fuel Cells by Spatially Resolved XAFS Techniques

Cited by 43 publications

References 49 publications

Operando XAFS Imaging of Distribution of Pt Cathode Catalysts in PEFC MEA

Operando XAFS Imaging of Distribution of Pt Cathode Catalysts in PEFC MEA

Imaging of Oxygen Diffusion in Individual Platinum/Ce2Zr2Ox Catalyst Particles During Oxygen Storage and Release

Experimental Methodologies to Understand Degradation of Nanostructured Electrocatalysts for PEM Fuel Cells: Advances and Opportunities

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Imaging of Oxygen Diffusion in Individual Platinum/Ce₂Zr₂O_x Catalyst Particles During Oxygen Storage and Release