Structure of Pt(111)/ionomer membrane interface and its bias-induced change in membrane electrode assembly

Masuda, Takuya*; Fukumitsu, Hitoshi*; Kondo, Toshihiro*; Naohara, Hideo*; Tamura, Kazuhisa; Sakata, Osami*; Uosaki, Kohei*

Journal of Physical Chemistry C, 117(23), p.12168 - 12171, 2013/06

https://doi.org/10.1021/jp402251z

The structure of the perfluorosulfonated ionomer (PFSI)/Pt(111) interface in a membrane electrode assembly (MEA)-like configuration of a polymer electrolyte membrane (PEM) fuel cell, that is, a vacuum evaporated Pt layer/PEM(Nafion membrane)/PFSI(adhesion Nafion layer)/Pt(111) single crystal, and its bias-induced change were investigated by surface X-ray scattering measurement at an atomic level. Crystal truncation rod measurement shows that PFSI adsorbed on the Pt(111)-(11) surface without bias. When the Pt(111) electrode was positively biased to form Pt oxide, the PFSI layer was detached from the Pt surface and oxygen atoms penetrated into the Pt lattice.

In situ electrochemical, electrochemical quartz crystal microbalance, scanning tunneling microscopy, and surface X-ray scattering studies on Ag/AgCl reaction at the underpotentially deposited Ag bilayer on the Au(111) electrode surface

Uosaki, Kohei*; Morita, Jun*; Katsuzaki, Tomoko*; Takakusagi, Satoru*; Tamura, Kazuhisa; Takahashi, Masamitsu; Mizuki, Junichiro; Kondo, Toshihiro*

Journal of Physical Chemistry C, 115(25), p.12471 - 12482, 2011/06

https://doi.org/10.1021/jp2010502

Ag/AgCl reaction at the Ag bilayer, which was underpotentially prepared on a Au(111) surface, was investigated using electrochemical quartz crystal microbalance (EQCM), scanning tunneling microscopy (STM), surface X-ray scattering (SXS), and electrochemical techniques. When the potential was scanned positively from -200 mV, the Cl ion was adsorbed on the Au(111) electrode surface around 0 mV, and then the phase transition of the adsorbed Cl ion layer from random orientation to ( ) structure took place at around +130 mV. The Ag bilayer and Cl ions were oxidatively reacted to form the AgCl monolayer with ( ) 13.9 structure around +200 mV, accompanied with the formation of AgCl monocrystalline clusters on the AgCl monolayer surface. The structure of the AgCl monolayer on the Au(111) surface was changed from ( )R13.9 structure to (44) structure around +500 mV.

Maintenance of seismic observation systems in HTTR

Kondo, Makoto; Iigaki, Kazuhiko; Motegi, Toshihiro; Emori, Koichi

JAEA-Testing 2009-002, 50 Pages, 2009/08

JAEA-Testing-2009-002.pdf:2.44MB

High Temperature engineering Test Reactor (HTTR) is a test reactor that build on sand layer formed during quaternary era. In principle, nuclear power generation facilities need to be supported on rigid rock formed during tertiary era, and now it is investigated to construct nuclear power generation facilities on sand layer formed during quaternary era for expanding suitable location. For this reason, we installed seismic observation systems in HTTR. And we have performed seismic safety evacuation using measured seismic acceleration in ground and building. This report compiles specifications of seismic observation systems, contents of check for seismic observation systems, check result of seismic observation systems and maintenance of seismic observation systems in HTTR.

Characteristics of Nicrosil versus Nisil thermocouples for the in-core temperature monitoring system in HTTR

Saito, Kenji; Shimizu, Atsushi; Hirato, Yoji; Kondo, Makoto; Kawamata, Takanori; Nemoto, Masumi; Motegi, Toshihiro

JAEA-Technology 2009-015, 52 Pages, 2009/05

JAEA-Technology-2009-015.pdf:10.17MB

As In-core temperature monitoring system, Type N thermocouples arranged at hot plenum block measures the primary coolant temperature at each hot plenum block in order to monitor the condition of the reactor core during the reactor operation. Type N thermocouples should have a long lifetime with high reliability under the high temperature environment of about 1000C, because they are used in HTTR reactor pressure vessel. This report shows that the characteristic change of Type N thermocouples was confirmed from operation and maintenance data of current HTTR.

Test results of HTTR control system

Motegi, Toshihiro; Iigaki, Kazuhiko; Saito, Kenji; Sawahata, Hiroaki; Hirato, Yoji; Kondo, Makoto; Shibutani, Hideki; Ogawa, Satoru; Shinozaki, Masayuki; Mizushima, Toshihiko; et al.

JAEA-Technology 2006-029, 67 Pages, 2006/06

JAEA-Technology-2006-029.pdf:3.07MB

The plant control performance of the IHX helium flow rate control system, the PPWC helium flow rate control system, the secondary helium flow rate control system, the inlet temperature control system, the reactor power control system and the outlet temperature control system of the HTTR are obtained through function tests and power-up tests. As the test results, the control systems show stable control response under transient condition. Both of inlet temperature control system and reactor power control system shows stable operation from 30% to 100%, respectively. This report describes the outline of control systems and test results.

Investigation of automatic shutdown of HTTR on May 21st, 2003

Hirato, Yoji; Saito, Kenji; Kondo, Makoto; Sawahata, Hiroaki; Motegi, Toshihiro; Tsuchiyama, Masaru*; Ando, Toshio*; Mizushima, Toshihiko; Nakazawa, Toshio

JAERI-Tech 2004-037, 33 Pages, 2004/04

JAERI-Tech-2004-037.pdf:4.08MB

HTTR (High Temperature Engineering Test Reactor) was operated from May 6th, 2003 to June 18th, 2003 to obtain operation data in parallel loaded operation mode and in safety demonstration tests. Operated with the reactor power at 60% of the rated power on May 21st, HTTR was automatically scrammed by a signalof "Primary coolant flow rate of the Primary Pressurized Water Cooler (PPWC): Low". The cause of the shutdown was the primary gas circulator (A) automatically stopped. The primary coolant flow rate of the PPWC decresed and reached the scram set value due to the gas circulator stop. As a result of investigation, it became clear that the cause of the gas circulator stop was malfunction of an auxiliary relay which monitored electric power of a circuit breaker in power line of the gas circulator. The cause of malfunction was deterioration of the relay under high temperature condition because the relay was installed beside an electric part which was heated up by electricity.

Growth process of Pd thin layers on Au electrode surfaces

Takahashi, Masamitsu; Mizuki, Junichiro; Tamura, Kazuhisa*; Kondo, Toshihiro*; Uosaki, Kohei*

Shinku, 44(3), P. 375, 2001/03

https://doi.org/10.3131/jvsj.44.326

no abstracts in English

Crystal structures of two coupled enzymes accomplishing high-efficient biochemical synthesis of trehalose

Okazaki, Nobuo; Tamada, Taro; Miura, Yutaka*; Feese, M. D.*; Kato, Masaru*; Komeda, Toshihiro*; Takehara, Kyoko*; Kobayashi, Kazuo*; Kondo, Keiji*; Kuroki, Ryota

no journal, , 

The crystal structure of glycosyltrehalose synthase (GTSase) from the hyperthermophilic archaeum Sulfolobus shibatae DSM5389 has been determined to 2.3 A resolution by X-ray crystallography. GTSase converts the glucosidic bond between the last two glucose residues of amylose from an alpha-1,4 bond to an alpha-1,1 bond, making a non-reducing glycosyl trehaloside in the first step of the biosynthesis of trehalose. The structure of GTSase can be divided into five domains. The central domain has the (beta/alpha)8 barrel fold which is conserved in the alpha-amylase family as the catalytic domain. Three invariant catalytic carboxylic amino acids in the alpha-amylase family are also found in GTSase at positions Asp241, Glu269 and Asp460 in the (beta/alpha)8 domain. Our previous study with KM1-GTSase has been shown that the maltooligosaccharides are converted to glycosyltrehalose by an intramolecular transglycosylation mechanism.