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In this work, we performed transient reflection measurements using the pump–probe protocol to investigate the influence of lattice defects induced by 380 keV argon (Ar) ions on the phonon dynamics of interlayer shearing (E 2 g 1 ) and in-plane carbon stretching (E 2 g 2 ) modes in highly oriented pyrolytic graphite (HOPG). The frequency and decay rate of E 2 g 1 - and E 2 g 2 -mode phonons were changed significantly at the fluence of 1 × 10 14 ions/cm 2. This indicated that significant structural changes in HOPG due to 380 keV Ar-ion irradiation were expressed as changes in the frequency and decay rate of phonons. In HOPG irradiated with 380 keV Ar + at the fluence of 1 × 10 14 ions/cm 2 , our measurement results indicated that compressive and tensile stresses contributed to in-plane and interlayer graphite structures, respectively. [ABSTRACT FROM AUTHOR]

Glassy carbon substrates were implanted with 100 keV platinum ions. The implanted samples were analyzed using cross-sectional transmission electron microscopy (TEM) and x-ray photoelectron spectroscopy. Ion beam sputtering significantly affected the depth profile during platinum-ion implantation. Cross-sectional TEM revealed that the implanted platinum atoms were in the amorphous state and did not aggregate. Chemical state analysis of the platinum-ion-implanted glassy carbon substrates suggested that lattice defects in the substrates owing to the platinum-ion implantation caused the platinum–carbon interaction with electron transfer from platinum to carbon. [ABSTRACT FROM AUTHOR]

Proton exchange membrane fuel cells (PEMFCs) have attracted considerable attention as distributed power sources for automotive and residential applications. In PEMFCs, platinum (Pt) nanoparticles supported on carbon materials are used as electrocatalysts for oxygen reduction reactions. However, improved durability of the electrocatalysts is urgently required for commercialization purposes. We describe an ion implantation technique for the preparation of Pt nanoparticles with superior catalytic properties, suitable for fuel cell applications. The Pt nanoparticles were obtained by implanting a glassy carbon (GC) substrate with 100 keV Pt-ions, followed by electrochemical etching and a heat treatment. Electrochemical measurements of the Pt nanoparticles prepared by the proposed implantation technique demonstrated superior durability when compared to those prepared by the conventional magnetron sputtering method. We suggested that the defective structure of the GC substrate, caused by the Pt-ion implantation, has led to the improved electrochemical stability of the GC substrate and Pt-carbon support interactions, thereby enhancing the durability of our Pt nanoparticles. [ABSTRACT FROM AUTHOR]

X-ray absorption spectroscopy measurements were performed for the C K-edge of Pt nanoparticles on Ar+-irradiated carbon supports in order to elucidate the origin of improved catalyst performance after the introduction of vacancies into the carbon support. We observed a change in the electronic structure at the interface between the Pt nanoparticles and the carbon support after vacancy introduction, which is in good agreement with theoretical results. The results indicated that vacancy introduction resulted in a drastic change in the Pt–C interactions, which likely affected the d-band center of the Pt nanoparticles and led to the enhancement of the oxygen reduction reaction in catalysts. [ABSTRACT FROM AUTHOR]

The ion beam-induced defects in carbon supports for platinum (Pt) nanoparticles have been found to enhance the catalytic activity. Highly oriented pyrolytic graphite (HOPG) was irradiated with 380 keV argon ions (Ar + ), and Pt nanoparticles were then deposited on it by a radio frequency (rf) magnetron sputtering method. The Pt nanoparticle size on Ar + -irradiated HOPG and the carbon structure at the interface were investigated by transmission electron microscope (TEM) and Raman spectroscopy, respectively. The observed size of Pt nanoparticles on the irradiated HOPG was larger than that on the non-irradiated HOPG. Raman spectra indicated that vacancy-like defects were formed on the HOPG surface by Ar + -irradiation at the fluences between 1.0 × 10 12 and 1.0 × 10 13 ions/cm 2 , and sp 3 defects were induced by irradiation more than 5.0 × 10 13 ions/cm 2 . These defective structures on the HOPG would promote the Pt particle growth. [ABSTRACT FROM AUTHOR]

X-ray absorption spectroscopy measurements were performed for the C K-edge of Pt nanoparticles on Ar + -irradiated carbon supports in order to elucidate the origin of improved catalyst performance after the introduction of vacancies into the carbon support. We observed a change in the electronic structure at the interface between the Pt nanoparticles and the carbon support after vacancy introduction, which is in good agreement with theoretical results. The results indicated that vacancy introduction resulted in a drastic change in the Pt-C interactions, which likely affected the d-band center of the Pt nanoparticles and led to the enhancement of the oxygen reduction reaction in catalysts.