Updated on 2025/03/28

写真a

 
SAMJESKE Gabor Arwed
 
Organization
Graduate School of Science Professor
Graduate School
Graduate School of Science
Undergraduate School
School of Science Department of Chemistry
Title
Professor
External link

Degree 1

  1. Dr. rer. nat. ( 2003.5   Bonn University ) 

Research Interests 1

  1. fuel cell catalysts, catalyst synthesis, XAFS

Research History 1

  1. The University of Electro-Communications Innovation Research Center for Fuel Cells   Project Professor

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Professional Memberships 5

  1. Electrochemical Society of Japan

  2. Chemical Society of Japan

  3. International Society of Electrochemistry

  4. Electrochemical Society

  5. American Chemical Society

 

Papers 34

  1. Variation of Local Structure and Reactivity of Pt/C Catalyst for Accelerated Degradation Test of Polymer Electrolyte Fuel Cell Visualized by Operando 3D CT-XAFS Imaging Reviewed International journal

    CHEMNANOMAT   Vol. 8 ( 4 )   2022.4

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    Language:Japanese   Publishing type:Research paper (scientific journal)  

    DOI: 10.1002/cnma.202200008

    Web of Science

    Scopus

  2. <i>Operando</i> Imaging of Ce Radical Scavengers in a Practical Polymer Electrolyte Fuel Cell by 3D Fluorescence CT-XAFS and Depth-Profiling Nano-XAFS-SEM/EDS Techniques Reviewed International journal

    Matsui, H; Takao, S; Higashi, K; Kaneko, T; Samjeské, G; Uruga, T; Tada, M; Iwasawa, Y

    ACS APPLIED MATERIALS & INTERFACES   Vol. 14 ( 5 ) page: 6762 - 6776   2022.2

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:ACS Applied Materials and Interfaces  

    There is little information on the spatial distribution, migration, and valence of Ce species doped as an efficient radical scavenger in a practical polymer electrolyte fuel cell (PEFC) for commercial fuel cell vehicles (FCVs) closely related to a severe reliability issue for long-term PEFC operation. An in situ three-dimensional fluorescence computed tomography-X-ray absorption fine structure (CT-XAFS) imaging technique and an in situ same-view nano-XAFS-scanning electron microscopy (SEM)/energy-dispersive spectrometry (EDS) combination technique were applied for the first time to perform operando spatial visualization and depth-profiling analysis of Ce radical scavengers in a practical PEFC of Toyota MIRAI FCV under PEFC operating conditions. Using these in situ techniques, we successfully visualized and analyzed the domain, density, valence, and migration of Ce scavengers that were heterogeneously distributed in the components of PEFC, such as anode microporous layer, anode catalyst layer, polymer electrolyte membrane (PEM), cathode catalyst layer, and cathode microporous layer. The average Ce valence states in the whole PEFC and PEM were 3.9+ and 3.4+, respectively, and the Ce3+/Ce4+ ratios in the PEM under H2 (anode)-N2 (cathode) at an open-circuit voltage (OCV), H2-air at 0.2 A cm-2, and H2-air at 0.0 A cm-2 were 70 ± 5:30 ± 5%, as estimated by both in situ fluorescence CT-X-ray absorption near-edge spectroscopy (XANES) and nano-XANES-SEM/EDS techniques. The Ce3+ migration rates in the electrolyte membrane toward the anode and cathode electrodes ranged from 0.3 to 3.8 μm h-1, depending on the PEFC operating conditions. Faster Ce3+ migration was not observed with voltage transient response processes by highly time-resolved (100 ms) and spatially resolved (200 nm) nano-XANES imaging. Ce3+ ions were suggested to be coordinated with both Nafion sulfonate (Nfsul) groups and water to form [Ce(Nfsul)x(H2O)y]3+. The Ce migration behavior may also be affected by the spatial density of Ce, interactions of Ce with Nafion, thickness and states of the PEM, and H2O convection, in addition to the PEFC operating conditions. The unprecedented operando imaging of Ce radical scavengers in the practical PEFCs by both in situ three-dimensional (3D) fluorescence CT-XAFS imaging and in situ depth-profiling nano-XAFS-SEM/EDS techniques yields intriguing insights into the spatial distribution, chemical states, and behavior of Ce scavengers under the working conditions for the development of next-generation PEFCs with high long-term reliability and durability.

    DOI: 10.1021/acsami.1c22336

    Web of Science

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    PubMed

  3. Ultrafine Pt-Ni nanoparticles in hollow porous carbon spheres for remarkable oxygen reduction reaction catalysis Reviewed International journal

    Wan, XK; Samjeské, G; Matsui, H; Chen, C; Muratsugu, S; Tada, M

    DALTON TRANSACTIONS   Vol. 50 ( 20 ) page: 6811 - 6822   2021.5

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:Dalton Transactions  

    Ultrafine bimetallic Pt-Ni nanoparticles, which catalyze the oxygen reduction reaction (ORR) efficiently, were successfully prepared in hollow porous carbon spheres (HPCSs) under the assistance of organic molecules. 2,2′-Dipyridylamine (dpa) was found to be most effective in preparing homogeneous small Pt-Ni nanoparticles (2.0 ± 0.4 nm) without the phase separation of Pt and Ni during synthesis, and the assistance of the organic molecules was investigated for the alloy nanoparticle formation. The Pt-Ni nanoparticle/HPCS catalyst synthesized in the presence of dpa exhibited remarkable electrochemical performance in the ORR showing a high mass activity of 3.25 ± 0.14 A mg-1Pt at 0.9 VRHE (13.5-fold higher relative to a commercial Pt/C catalyst), a large electrochemical surface area of 105 ± 8 m2 g-1Pt, and high durability. After 60 000 cycles of accelerated durability testing, the mass activity was still 12.3 times higher than that of the commercial Pt/C catalyst.

    DOI: 10.1039/d1dt00647a

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  4. Visualization and understanding of the degradation behaviors of a PEFC Pt/C cathode electrocatalyst using a multi-analysis system combining time-resolved quick XAFS, three-dimensional XAFS-CT, and same-view nano-XAFS/STEM-EDS techniques Reviewed International journal

    Higashi, K; Takao, S; Samjeské, G; Matsui, H; Tada, M; Uruga, T; Iwasawa, Y

    PHYSICAL CHEMISTRY CHEMICAL PHYSICS   Vol. 22 ( 34 ) page: 18919 - 18931   2020.9

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    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Physical Chemistry Chemical Physics  

    We developed a multi-analysis system that can measure in situ time-resolved quick XAFS (QXAFS) and in situ three-dimensional XAFS-CT spatial imaging in the same area of a cathode electrocatalyst layer in a membrane-electrode assembly (MEA) of a polymer electrolyte fuel cell (PEFC) at the BL36XU beamline of SPring-8. The multi-analysis system also achieves ex situ two-dimensional nano-XAFS/STEM-EDS same-view measurements of a sliced MEA fabricated from a given place in the XAFS-CT imaged area at high spatial resolutions under a water-vapor saturated N2 atmosphere using a same-view SiN membrane cell. In this study, we applied the combination method of time-resolved QXAFS/3D XAFS-CT/2D nano-XAFS/STEM-EDS for the first time for the visualization analysis of the anode-gas exchange (AGEX) (simulation of the start-up/shut-down of PEFC vehicles) degradation process of a PEFC MEA Pt/C cathode. The AGEX cycles bring about serious irreversible degradation of both Pt nanoparticles and carbon support due to a spike-like large voltage increase. We could visualize the three-dimensional distribution and two-dimensional depth map of the amount, oxidation state (valence), Pt2+ elution, detachment, and aggregation of Pt species and the formation of carbon voids, where the change and movement of the Pt species in the cathode catalyst layer during the AGEX cycles did not proceed exceeding the 1 μm region. It is very different from the case of an ADT (an accelerated durability test between 0.6-1.0 VRHE)-degraded MEA. We discuss the spatiotemporal behavior of the AGEX degradation process and the degradation mechanism.

    DOI: 10.1039/d0cp01356k

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  5. Feed gas exchange (startup/shutdown) effects on Pt/C cathode electrocatalysis and surface Pt-oxide behavior in polymer electrolyte fuel cells as revealed using <i>in situ</i> real-time XAFS and high-resolution STEM measurements Reviewed International journal

    Samjeské, G; Kaneko, T; Gunji, T; Higashi, K; Uruga, T; Tada, M; Iwasawa, Y

    PHYSICAL CHEMISTRY CHEMICAL PHYSICS   Vol. 22 ( 17 ) page: 9424 - 9437   2020.5

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:Physical Chemistry Chemical Physics  

    The synchronizing measurements of both cyclic voltammograms (CVs) and real-time quick XAFSs (QXAFSs) for Pt/C cathode electrocatalysts in a membrane electrode assembly (MEA) of polymer electrolyte fuel cells (PEFCs) treated by anode-gas exchange (AGEX) and cathode-gas exchange (CGEX) cycles (startup/shutdown conditions of FC vehicles) were performed for the first time to understand the opposite effects of the AGEX and CGEX treatments on the Pt/C performance and durability and also the contradiction between the electrochemical active surface area (ECSA) decrease and the performance increase by CGEX treatment. While the AGEX treatment decreased both the ECSA and performance of MEA Pt/C due to carbon corrosion, it was found that the CGEX treatment decreased the ECSA but increased the Pt/C performance significantly due to high-index (331) facet formation (high-resolution STEM) and hence the suppression of strongly bound Pt-oxide formation at cathode Pt nanoparticle surfaces. Transient QXAFS time-profile analysis for the MEA Pt/C also revealed a direct relationship between the electrochemical performance or durability and transient kinetics of the Pt/C cathode.

    DOI: 10.1039/c9cp06895c

    Web of Science

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Presentations 3

  1. Nitrogen-doped Hollow Porous Carbon Sphere Encapsulated PtNixRhy-alloy Nanoparticles as Methanol Oxidation Electrocatalysts in Alkaline Electrolyte

    Gabor Samjeske, Xian-Kai Wan, Hirosuke Matsui, Takeshi Tokida, Chaoqi Chen, Satoshi Muratsugu, Mizuki Tada

    102nd CSJ Annual Meeting  2022.3.25  The Chemical Society of Japan

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    Event date: 2022.3

    Language:English   Presentation type:Oral presentation (general)  

    Venue:Online  

  2. On-site SO2 poisoning of PEFC Pt Cathode Catalyst for operando Pt LIII-edge XAFS analysis

    Koshin Sato, Hirosuke Matsui, Gabor Samjeske, Tomoya Uruga, Mizuki Tada

    102nd CSJ Annual Meeting  2022.3.25  The Chemical Society of Japan

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    Event date: 2022.3

    Language:Japanese   Presentation type:Oral presentation (general)  

    Venue:Online Meeting  

  3. Enhanced Oxygen Reduction Reaction Activity and Durability by 2,2'-Dipyridylamine Assisted Encapsulation of PtNi Nanoparticles into Hollow Porous Carbon Spheres

    Gabor Samjeske, Xian-Kai Wan, Hirosuke Matsui, Chaoqi Chen, Satoshi Muratsugu, Mizuki Tada

    101st CSJ Annual Meeting (2021)  2021.3.19  The Chemical Society of Japan

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    Event date: 2021.3

    Language:English   Presentation type:Oral presentation (general)  

    Venue:Online Meeting  

 

Teaching Experience (On-campus) 1

  1. Core Inorganic Chemistry

    2021