著者

Shrivastava Udit N. Suetsugu Kota Nagano Shusaku Fritzsche Helmut Nagao Yuki Karan Kunal

出版者

Royal Society of Chemistry

雑誌

Soft Matter (ISSN:1744683X)

巻号頁・発行日

vol.16, no.5, pp.1190-1200, 2019-12-16

被引用文献数

21

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Nanometer thin films of Nafion ionomer interfacing with platinum form the functional electrode in many electrochemical devices including fuel cells and electrolyzers. To impart facile proton conduction in Nafion ionomer, sufficient hydration of Nafion ionomer is necessary to create a percolating network of water-filled nanometer sized hydrophilic domains that manifests as macroscopic swelling. This hydration behavior of ionomer thin films is poorly understood especially for films confined on electrochemically relevant Pt substrates. In this work, we present the evolution of hydration-dependent microscopic hydrophilic domains and macroscopic expansion of 55 nm thin Nafion film on a Pt substrate. The cross-correlation among the film macro-expansion from ellipsometry, the micro-expansion from GISAXS, and the water distribution from neutron reflectometry (NR), explains the observed non-affine behavior of the film which can be attributed to the randomly and spatially non-uniform distribution of water domains. A correlation between macroscopic factor (ε/τ) for protonic conductivity, and the domain size and swelling is presented for the first time. In addition, interfacial water between Pt and the ionomer interface estimated at 75% and 84% RH, and increase in domain size with RH, are discussed to explain increased activity and oxygen diffusivity with RH.

著者

Hasan Md. Mahmudul Rakib Riad Hussain Hasnat Mohammad Abul Nagao Yuki

出版者

American Chemical Society

雑誌

ACS Applied Energy Materials (ISSN:25740962)

巻号頁・発行日

vol.3, no.3, pp.2907-2915, 2020-02-24

被引用文献数

15

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Well-defined silver dendrite nanostructures with primary and secondary branches on a glassy carbon electrode (GCE) surface are first demonstrated using a simple wet chemical electroless deposition method without any aid of a surfactant. The properties of dendrite structures were characterized using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). Results of XPS and XRD indicated that most of the silver particles were not oxidized. The obtained silver dendrite GCE (Ag/GCE) showed high electrochemical activity towards catalytic oxidation for ascorbic acid (AA). The oxidation process followed a stepwise mechanism at slower scan rates (υ < 0.15 V s^<-1>) and a concerted mechanism at faster scan rates (υ > 0.15 V s^<-1>). The silver nanostructures are highly stable on the GCE surface and could be employed as an anode for an AA fuel cell.

著者

Salma Umme Zhang Dishen Nagao Yuki

出版者

Wiley-VCH

雑誌

Wiley ChemistrySelect (ISSN:23656549)

巻号頁・発行日

vol.5, no.4, pp.1255-1263, 2020-01-24

被引用文献数

14

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After a fluorene-based anion exchange membrane (AEM) containing 1-isopropyl-2-methylimidazolium with alkyl side chains was prepared, the membrane properties, including OH– conductivities, ion exchange capacity (IEC), water uptake, swelling ratio, and chemical and thermal stabilities of the obtained membrane were assessed. The synthesized membrane exhibited low water uptake and good dimensional stability with adequate hydroxide conductivity. For example, the AEM showed a swelling ratio of 7% and hydroxide conductivity of 46 mS cm^<-1> at 80°C in liquid water. The chemical stability was investigated in 1 M NaOH solution at room temperature and at 80°C. At both temperatures, degradation of the imidazolium cationic groups was observed, although the main chain was chemically stable. All results obtained from this research are expected to provide important direction and insight for AEM synthesis for practical applications in anion exchange membrane fuel cells.

著者

Uddin S. M. Nizam Laokroekkiat Salinthip Rashed Md. Abu Mizuno Shino Ono Kenta Ishizaki Manabu Kanaizuka Katsuhiko Kurihara Masato Nagao Yuki Hamada Tsutomu

出版者

Royal Society of Chemistry

雑誌

Chemical Communications (ISSN:0009241X)

巻号頁・発行日

vol.56, no.7, pp.1046-1049, 2019-12-23

被引用文献数

5

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A new type of artificial giant liposome incorporating ion transport channels and using nanoparticles of metal organic frameworks was demonstrated. The micropores of Prussian blue nanoparticles served as ion transport channels between the outer and inner phases of liposomes.