Mesoporous Carbon Fibers with Tunable Mesoporosity for Electrode Materials in Energy Devices.

To improve the properties of mesoporous carbon (MC), used as a catalyst support within electrodes, MC fibers (MCFs) were successfully synthesized by combining organic-organic self-assembly and electrospinning deposition and optimizing heat treatment conditions. The pore structure was controlled by varying the experimental conditions. Among MCFs, MCF-A, which was made in the most acidic condition, resulted in the largest pore diameter (4-5 nm), and the porous structure and carbonization degree were further optimized by adjusting heat treatment conditions. Then, since the fiber structure is expected to have an advantage when MCFs are applied to devices, MCF-A layers were prepared by spray printing. For the resistance to compression, MCF-A layers showed higher resistance (5.5% change in thickness) than the bulk MC layer (12.8% change in thickness). The through-plane resistance was lower when the fiber structure remained more within the thin layer, for example, +8 mΩ for 450 rpm milled MCF-A and +12 mΩ for 800 rpm milled MCF-A against the gas diffusion layer (GDL) 25BC carbon paper without a carbon layer coating. The additional advantages of MCF-A compared with bulk MC demonstrate that MCF-A has the potential to be used as a catalyst support within electrodes in energy devices.

Development of Porous Pt Electrocatalysts for Oxygen Reduction and Evolution Reactions.

Porous Pt electrocatalysts have been developed as an example of carbon-free porous metal catalysts in anticipation of polymer electrolyte membrane (PEM) fuel cells and PEM water electrolyzers through the assembly of the metal precursor and surfactant. In this study, porous Pt was structurally evaluated and found to have a porous structure composed of connected Pt particles. The resulting specific electrochemical surface area (ECSA) of porous Pt was 12.4 m2 g-1, which was higher than that of commercially available Pt black. Accordingly, porous Pt showed higher oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) activity than Pt black. When the activity was compared to that of a common carbon-supported electrocatalyst, Pt/ketjen black (KB), porous Pt showed a comparable ORR current density (2.5 mA cm-2 at 0.9 V for Pt/KB and 2.1 mA cm-2 at 0.9 V for porous Pt), and OER current density (6.8 mA cm-2 at 1.8 V for Pt/KB and 7.0 mA cm-1 at 1.8 V), even though the ECSA of porous Pt was only one-sixth that of Pt/KB. Moreover, it exhibited a higher durability against 1.8 V. In addition, when catalyst layers were spray-printed on the Nafion® membrane, porous Pt displayed more uniform layers in comparison to Pt black, showing an advantage in its usage as a thin layer.

Frequency of SCEs in Japanese infants exposed to dioxins and PCBs through the breast milk.

Frequency of sister chromatid exchanges (SCEs), which has been considered an index to the synthetic and sharp genotoxic and clastogenic potencies, was examined by using the infant lymphocytes postnatal of around ten months, in order to evaluate the genotoxic or clastogenic potency of exposures to PCBs and dioxins through the breast milk. SCE frequency (mean +/- S.D.) as the control culture treated with the solvent, DMSO, alone (SCEcontrol) was 8.3 +/- 1.1/cell and that as the culture treated with 7,8-benzoflavone (SCEANF) was 11.9 +/- 1.5/cell. In addition, the difference between SCEANF and SCEcontrol, that is, delta SCEs was calculated 3.6 +/- 1.5/cell. The intake of PCBs (mean +/- S.D.) through the breast milk in these infants was 133 +/- 85 mg/kg body weight and that of dioxins 24 +/- 13 TEQ-ng/kg body weight. PCBs intake in the average was about 5,500 times greater than that of dioxins. We however, could not find any significant effect of PCBs on the frequencies of SCEs. Dioxins, on the contrary, showed a significant negative relationship to the frequency of delta SCEs. Therefore, exposure to dioxins through the breast milk seemed to elicit some genotoxic or clastogenic effects on Japanese general infants postnatal of around ten months.

Frequency of SCEs in Japanese infants lactationally exposed to organochlorone pesticides.

Changes in the frequency of sister chromatid exchanges (SCEs) in cultured mammalian cells have been considered as indices to the synthetic and sharp genotoxic and clastogenic potencies. Frequency of SCEs in cultured lymphocyte obtained from infants postnatal of around ten months was examined to evaluate the genotoxic or clastogenic potency of lactational exposures to some organochlorine pesticides such as HCHs, DDT and chlordane in this study. Frequency (median, min.-max.) of SCEs as the control culture treated with the solvent, DMSO, alone (SCE control) was 8.0/cell, 6.5-12.4/cell, that as the culture treated with 7,8-benzoflavone (SCEANF) was 11.8/cell, 9.1-15.6/cell and the difference between SCEANF and SCEcontrol, that is, delta SCEs was 3.9/cell, 0.2:7.2/cell. Lactational exposures (median, min.-max.) to the three organochlorine pesticides were as follows: HCHs; 341 mg/kg body weight, 43-1449 mg/kg body weight, DDT; 272 mg/kg body weight, 33-1361 mg/kg body weight and chlordane; 69 mg/kg body weight, 13-379 mg/kg body weight. The median exposure level to chlordane through the breast milk was one fourth to one fifth times lower than that to HCHs or DDT and probably due to such small amounts of it's intake, we could not find any correlation of chlordane with frequencies of SCEcontrol, SCEANF and delta SCEs in cultured lymphocytes of Japanese infants postnatal of about ten months. In the meantime, frequencies of SCEcontrol and SCEANF showed increasing and decreasing tendencies with the increasing exposure to DDT and also HCHs through the breast milk. In consequence, the frequency of delta SCEs was significantly lowered. Therefore, lactational exposure to DDT and HCHs seemed to elicit some genotoxic or clastogenic effects on Japanese general infants at ages of around the months. These compounds were also considered rather potent S-dependent clastogens than non-S-dependent ones. So, further detailed studies are needed not only to get conclusive findings but also from this viewpoint.