Pt-Ni alloy thin films with various compositions were prepared by RF-magnetron sputtering, then their activity was evaluated. By combining a circular plate and rectangular plate of Pt and Ni as the target, Pt-Ni alloy thin films with various compositions were obtained. Although the oxygen reduction current of the Pt film and Ni film were 4.8 mA cm-2 and 1.0 mA cm-2, respectively, the oxygen reduction current of the Pt-Ni alloy thin film was higher than 5 mA cm-2. Among the Pt-Ni alloys, Pt72Ni28 showed the highest oxygen reduction current of 7.2 mA cm-2. These better activities of the Pt-Ni alloy thin films were caused by their higher active surface areas than that of the Pt thin film. It is postulated that the role of Ni increases the surface area by dissolution and inhibiting the oxidation of Pt. Especially, the Pt-Ni thin film with the Ni content higher than 90 at.% showed a higher oxygen reduction activity than Pt. Because the amount of Pt is able to be drastically reduced using the Pt-Ni alloy, it is a very promising material for the oxygen reduction reaction.
The flow of fresh water into the sea, known as submarine groundwater discharge, is one of key factors for understanding the hydrological cycle in sea and land regions. The numerous positions from which fresh water gushes and the amount impedes the understanding of its properties. In our previous study, we detected groundwater discharge points based on the difference between freshwater and seawater by using the Advanced Land Observing Satellite (ALOS) Advanced Visible and Near Infrared Radiometer type 2 (AVNIR-2) outputs with 10 m spatial resolution. Data available for analysis is limited because the AVNIR-2 sensor is a passive sensor that is affected by clouds. In the present study, we analyze the features of water properties around the groundwater discharge points by using ALOS Phased Array type L-band Synthetic Aperture Radar (PALSAR) with 10 m spatial resolution. The results obtained by the proposed method are compared with the results of ground survey and geological and classified maps obtained by AVNIR-2 outputs. The comparison results suggest that the proposed method is effective to analyze features of groundwater discharge points in coastal regions around Mt. Chokaisan.
m-Phenylene diamine-containing compounds were synthesized via a one-pot process and subsequently used as new precipitating agents (PA1 and PA2). The precipitation of Pd and Pt was studied using PA1 and PA2 as metal precipitants. While PA1 exclusively precipitated Pd from a HCl solution containing Pd, Pt, and base metals, PA2 achieved precipitation of both Pd and Pt from the metal-containing HCl solution. Mutual separation of Pd and Pt was achieved by using PA1 and PA2 in the first and second precipitation steps, respectively. Separation tests at varying agent loadings revealed that Pd and Pt were precipitated by forming of an ion-pair composed of a metal chloro-complex anion (i.e., [PdCl4]2－ or [PtCl6]2－) and one precipitating agent molecule (i.e., divalent cation). The stoichiometric ratio of the ion-pairs was in agreement with the atomic ratios estimated from X-ray photoelectron spectroscopy results. Since the precipitation mechanism herein was based on the formation of an ion-pair, the cations of the precipitating agents only recovered Pd and Pt chloro-complex anions when the cations of the base metals were present in the solution. The different hydrophobicities of the precipitating agents enabled mutual separation of Pd and Pt.
The dispersibility of single-walled carbon nanotubes (SWCNTs) in ketone solvents, acetone and methyl ethyl ketone (MEK), was studied. SWCNTs were successfully dispersed in ketone solvents by sonication and the concentrations of the SWCNT dispersions were increased with the sonication time. The size distribution and UV-Vis absorption measurements showed that the SWCNTs in MEK were uniformly and almost individually dispersed. The zeta potentials of the SWCNTs dispersed in ketone solvents negatively increased with the sonication time. Furthermore, the G/D ratios of the dispersed SWCNTs in MEK were decreased as the sonication time increased. The negative zeta potentials and the decrease in G/D ratios are considered owing to introduction of carboxylic acids induced by sonication in ketone solvents. Although the electrical conductivity of the SWCNTs dispersed in MEK was slightly decreased due to the defects, ketone solvents are practicable dispersing solvents for SWCNTs with relatively low boiling points and high accessibility. SWCNT dispersions in ketone solvents would be suitable for antistatic coatings and nano-fillers for polymer reinforcement.