We have been developing an X-ray photoelectron tracking imager based on a glass capillary plate (CP) gas detector for cosmic X-ray polarimetry applications. The optical imaging system consists of a CP gas detector filled with a noble-gas mixture and a cooled CCD camera coupled to an optical lens system. The performance of the optical imaging CP gas detector as an X-ray polarimeter was investigated with highly polarized, well-monochromized, and well-collimated X-ray beams at the synchrotron radiation facilities in SPring-8 and KEK-PF. Owing to the fine imaging capability of the optical imaging CP gas detector, images of X-ray photoelectron tracks were clearly observed for the polarized X-rays. A modulation factor of 26% was obtained for a 15 keV polarized X-ray beam, for which the energy resolution was 13%. We report on the properties of the optical imaging CP gas detector as an X-ray polarimeter and describe the outlook on future developments on the basis of the measured characteristics and the results of Monte Carlo simulations.
State‐sensitive XAFS was enabled combined with high‐energy‐resolution (ΔE = 0.3 eV@5.5 keV) X‐ray fluorescence spectrometry and applied to Au sites of An/TiO2 and Sn promoter sites of Pt‐Sn/SiO2. Each state of interfacial Au sites located on Ti/O atoms and negatively/positively charged Aun clusters was discriminated. Feasibility of more direct information of on‐site catalysis via frontier orbital‐sensitive XAFS was demonstrated.
Recent combined experimental and theoretical efforts have led to progress in the understanding of hydrogen oxidation and oxygen reduction reactions in fuel cells. The hydrogen anode in the polymer electrolyte fuel cell needs to be tolerant of CO concentrations in the tens of ppm in the reformed natural gas fuel. We have found that various Pt-M (M = Fe, Co, Ni, Ru) nanoparticulate alloys have significantly greater tolerance than pure Pt, and also, the area-specific hydrogen oxidation activity is higher. We have been able to explain the CO tolerance and catalytic activity with a novel metal-to-metal hydrogen spillover mechanism that is based on density functional theory calculations. The latter have also been supported by in situ spectroscopic measurements, both X-ray absorption and infrared reflection-absorption.
Two-dimensional X-ray absorption spectroscopy was carried out to observe the reaction distribution in a LiCoO2 composite electrode from the shift of the peak top energy in Co K-edge X-ray absorption spectra. The influence of ionic transportation to the inhomogeneous reaction was evaluated by using the model electrode, which sandwiched the LiCoO2 composite electrode between an aluminum foil and a polyimide ion blocking layer. When the model electrode was charged with the currents of 6, 9, and 12 mA cm–2, the observed capacities were 51, 20, and 12 mAh g–1 and the charged areas visualized from the shift of the peak top energy in Co K-edge X-ray absorption spectra were formed within ca. 700, 500, and 200 μm from the edge of the electrode, respectively. The observed reaction distribution indicated that the electrochemically active region decreases with increasing the current density because of the large potential loss of the electrochemical processes.
Abstract The generation of highly dispersed PdO over zeolite supports was studied using in situ energy-dispersive XAFS (DXAFS) technique. From the comparison with the Na-ZSM-5, it was found that the oxidation as well as the spontaneous dispersion of Pd was promoted through the interaction between PdO and acid sites of H-form zeolites.
Abstract Invited for this month′s cover is the group of Prof. Dr. Hiroki Habazaki at Hokkaido University with their collaborators from Kanagawa University, Kyoto University, and the National Institute of Advanced Industrial Science and Technology. The image shows the oxygen evolution reaction on brownmillerite‐type Ca 2 FeCoO 5 categorized as an oxygen‐deficiency‐ordered perovskite in a basic solution. The Communication itself is available at 10.1002/cssc.201700499 .
