Satoru Kosaka

Photodegradation of toluene over TiO2−xNx under visible light irradiation

We report the photooxidation of toluene over nitrogen doped TiO(2) (TiO(2-x)N(x)) under visible light irradiation. The photocatalytic oxidation of toluene in air over TiO(2-x)N(x) powders was studied using diffuse reflectance Fourier transform infrared spectroscopy (DRIFTS), gas chromatography (GC), ion chromatography (IC), and gas chromatography mass spectrometry (GC-MS), focusing on the photocatalytic decomposition processes of toluene. Results obtained indicate that toluene, weakly adsorbed on the catalyst surface, is initially photooxidized to benzaldehyde which adsorbs onto the TiO(2-x)N(x) surface more strongly, leading to the formation of ring-opening products such as carboxylic acids and aldehydes. No gaseous intermediates were detected during the photooxidation. Major intermediates adsorbed at the catalyst surface were oxalic acid, (COOH)(2), acetic acid, CH(3)COOH, formic acid, HCOOH, and pyruvic acid, CH(3)COCOOH, whereas more complicated carboxylic species, including propionic acid, CH(3)CH(2)COOH, isovaleric acid, (CH(3))(2)CHCH(2)COOH, and succinic acid, (CH(2)COOH)(2), were also found in the early stage of the photooxidation. These intermediate products were gradually photodegraded to CO(2) and H(2)O under visible light irradiation.

Nonreciprocal Propagation Characteristics of 526 GHz Submillimeter-Wave in Transversely Magnetized Two-Layer Parallel-Plate Waveguide Containing p-InSb Slab

The magnetic field dependence of 526 GHz submillimeter-wave propagation in two-layer waveguides containing p-type InSb slabs was studied in detail while varying the ambient temperature, and the results were compared with theoretical predictions. It was shown that, at the liquid nitrogen temperature, the submillimeter-wave propagation loss is very small, typically 0.3 dB/mm, and that fabrication of a submillimeter-wave image guide employing a p-InSb slab may be possible. At the dry ice temperature, slow surface wave resonance was clearly observed and a nonreciprocity of at least 15 dB was obtained with an insertion loss of 5 dB. These results indicate that the construction of nonreciprocal devices in submillimeter-wave monolithic integrated circuits may be possible. It is also suggested that this nonreciprocal wave propagation can be controlled by injecting plasma in the InSb slab.

Acetylene-Treated Titania Nanotube Arrays (TNAs) as Support for Oxygen Reduction Reaction (ORR) Platinum Thin Film Catalysts

AbstractPlatinum layers show higher specific oxygen reduction reaction (ORR) activities than nanoparticles, and smooth monolayers of platinum on polycrystalline gold have been achieved by electrodeposition from CO-saturated solutions. Since Pt monolayers are interesting catalytic systems, this methodology was attempted on acetylene-treated titania nanotubes (TNAs) with high conductivity. However, the investigation of the as-treated TNAs found that probably nanotubes with an oxygen-containing graphitic overlayer were formed. It was observed that deposition after partial oxidative removal of the overlayer led to very low ORR activities while deposition on the intact overlayer gave rise to the highest activities obtained in our research so far. This is attributed to a “tie-layer” effect, in which the carbon layer screens the negative effects of the underlying TiO2 layer. The interesting effects of the graphitic overlayer on the ORR activity of the Pt deposits on acetylene-treated TNAs offer a strategy to mitigate the unfavorable interactions of the Pt/TiO2 interface. However, the carbon layer in this study was found not to be stable upon potential cycling. Graphical AbstractOnly Gold Lets Platinum be Platinum: Monolayer amounts of Pt, electrodeposited under CO termination, so far, only show specific activities comparable to polycrystalline platinum if deposited on polycrystalline gold. TiO2 modifications as supports facilitate higher activities only at enhanced conductivities, which usually sacrifice their stability.

Possibility of Submillimeter Slow Surface Wave Resonance in a Two-Layer Parallel-Plate Waveguide Containing n-Type or p-Type InSb Slab

The magnetic field dependence of submillimeter wave propagation in a two-layer parallel-plate waveguide containing n-type or p-type InSb slab has been experimentally studied at 526 GHz and 671 GHz. In each case, a resonant peak appeared on the transmission corresponding to the theoretically predicted slow surface wave resonance. Particularly with n-InSb, nonreciprocity of at least 20 dB was experimentally observed for transmission at the applied magnetic field of 0.2 T.

CO-Terminated Pt/Au Codeposition on Titania Nanotube Arrays (TNAs)

AbstractForming platinum monolayers on less-expensive materials is an ingenious way to enhance the mass activities for oxygen reduction reaction (ORR) and decrease the amount of this scarce and precious metal in fuel cell technology. Previously, we observed low activities of Pt catalysts deposited directly on titania nanotube arrays (TNAs). Here, we propose a gold interlayer between Pt and TiO2. The synthesis is attempted by the codeposition of Pt and Au from CO-saturated solution. The activity of the Pt/Au codeposited catalyst is higher than in the case when Pt is deposited alone. This result suggests that Au is a promising way to enhance ORR activity. The activity of this catalyst, however, is still much lower than that of the Pt monolayer on bulk gold. This is explained by the negative effects of CO, disrupting the chance of monolayer formation by preadsorption to the TNA substrate. Graphical AbstractCO-terminated Pt/Au codeposition on titania nanotube arrays (TNAs)

The Native Oxide on Titanium Metal as a Conductive Model Substrate for Oxygen Reduction Reaction Studies

AbstractVery thin Pt layers on inexpensive substrates are promising oxygen reduction reaction (ORR) catalysts for polymer electrolyte fuel cells (PEFCs). TiOx is considered a suitable substrate but shows problems with conductivity, thus masking chemical effects by semiconductor effects (mismatch in energy states hindering electron transport). The native oxide on metallic Ti (TiOx/Ti) has been used as a novel and promising model substrate for ORR studies eliminating semiconductor effects. A high-coverage “particle” layer with high specific ORR activity was formed via electrodeposition from Ar-saturated solution. While high specific activities could be demonstrated, the concept could not be enhanced to high mass activities by limiting the Pt deposition amount. The approach to quench Pt deposition by introducing CO failed due to its adsorption to the TiOx/Ti substrate before metal deposition and thus the prevention of layer formation. A similar approach for the Pt/Au codeposition was also unsuccessful manifesting the TiOx/Ti-CO incompatibility even further. Graphical AbstractCO, blessing, and curse: Pt deposition from Ar-saturated solution leads to a “film”-like deposit with high specific ORR activity. In contrast, the corresponding CO-saturated solution leads to deposition termination but a smooth monolayer is not formed due to interaction of CO with the TiOx/Ti substrate and, consequently, very low ORR activity is obtained.

Nonreciprocal propagation characteristics of 671 GHz submillimeter wave in image guide consisting of transversely magnetized p-InSb slab

The temperature and magnetic field dependences of 671 GHz submillimeter-wave propagation characteristics in a transversely magnetized image guide consisting of a p-InSb slab have been studied experimentally and theoretically. The result of the theoretical analysis indicates that the propagation loss of this image guide is as small as about 0.116 dB/mm at liquid-nitrogen temperature. As the sample temperature increases to 240 K, a surface wave resonance occurs and a nonreciprocity of more than 20 dB appears in the transmission in an applied magnetic field B of 0.45 T. Experimentally observed results are in good quantitative agreement with theoretical predictions. These findings indicate the possibility of fabricating nonreciprocal devices embedded in a submillimeter-wave image guide consisting of a p-InSb slab. It is also shown that the attenuation of and nonreciprocity in the wave propagation in this image guide can be controlled by injecting plasma into the p-InSb slab.

Inductively Coupled Plasma Mass Spectrometry Study on the Increase in the Amount of Pr Atoms for Cs-Ion-Implanted Pd/CaO Multilayer Complex with Deuterium Permeation

To investigate the nuclear transmutation of Cs into Pr reported in this journal by Iwamura and coworkers, we have measured the amount of Pr atoms in the range as low as ~1×1010 cm-2 using inductively coupled plasma mass spectrometry for Cs-ion-implanted Pd/CaO multilayer complexes before and after deuterium permeation. The amount of Pr was initially at most 2.0×1011 cm-2 and it increased up to 1.6×1012 cm-2 after deuterium permeation. The increase in the amount of Pr could be explained neither by deuterium permeation-stimulated segregation of Pr impurities nor by external contamination from the experimental environment during the permeation. No increase in Pr was observed for permeation with hydrogen. These findings suggest that the observed increase in Pr with deuterium permeation can be attributed to a nuclear origin, as reported by Iwamura and coworkers, although the amount of the increase in Pr is two orders of magnitude less than that reported by them.

Seventy GHz slow surface wave propagation in a waveguide containing transversely magnetized p-type and n-type InSb slabs

Wave propagation characteristics in a 70 GHz waveguide containing transversely magnetized p-type and n-type InSb slabs have been studied experimentally. Surface wave resonance occurs in this configuration. It is also shown that the magnetic field required for slow surface wave resonance is greatly reduced by the addition of the p-layer.