ring energy of 2.5 GeV and a stored current of 250-350 mA
(Proposal No. 2014P003) in a transmittance mode. The storage
ring was operated at 8 GeV. A Si(111) single crystal was used
to obtain a monochromatic X-ray beam. The EXAFS analysis
was performed using the REX version 2.5 program (RIGAKU).
The parameters for the EXAFS analyses were provided by
the FEFF6.
Energy-Dispersive X-ray (EDX) Spectroscopy: EDX was
measured with a Shimadzu Rayny EDX-700HS. The operating
tube current and voltage were 100 ¯A and 15 kV, respectively.
Rh was used as X-ray tube.
2. Experimental
2.1 Materials. Graphite (SP-1) was purchased from BAY
CARBON Inc. Single-wall carbon nanotube was purchased
from Carbon Solutions Inc. NaNO3, KMnO4, H2SO4, H2O2,
poly(methylhydrosiloxane) (PMHS) and hydrazine hydrate
were purchased from Wako Pure Chemical Industries, Ltd.
1,1,3,3-Tetramethyldisiloxane, MePh2SiH, NaBH4, Et3SiH,
and 1,5-cyclooctadiene were purchased from Tokyo Chemical
Industries Co., Ltd. IrO2, ethylene glycol, and 1,4-dioxane were
purchased from Kanto Chemical Co., Ltd. Activated carbon,
PtO2, and Ir were purchased from Aldrich Chemical Co. PtCl2,
PdCl2, RhCl3¢3H2O, and (NH4)2[IrCl6] were purchased from
Tanaka Kikinzoku International k.k. EtOH was purchased from
Kishida Chemical Co., Ltd. All reagents were used without
further purification. [IrCl(cod)]2 was prepared from (NH4)2-
[IrCl6] and 1,5-cyclooctadiene (cod). [Ir(OMe)(cod)]2 was
synthesized from [IrCl(cod)]2.
2.2 Methods. Transmission Electron Microscope (TEM)
Measurement: TEM images were collected from sample
powder dispersed on a carbon-coated copper grid. A STEM
microscope (JEOL JEM-2100F) equipped with a CEOS spheri-
cal aberration corrector (Cs-corrector) was operated at an
acceleration voltage of 200 kV.
X-ray Photoelectron Spectroscopy (XPS) Measurement:
XPS spectra were collected using a monochromatic Al Kα
X-ray source at 1486.6 eV (Shimadzu, Kratos AXIS Ultra) and
operated at 150 W, 15 kV, and 10 mA with a base pressure in
the XPS analysis chamber of 5 © 10¹8 Torr. High-resolution
spectra (C1s and Pt4f) were acquired using pass energy of 20
and 0.1 eV energy steps. All binding energies were referenced
to the hydrocarbon C1s peak at 284.5 eV.
Zeta Potential Measurement: Zeta potential of sample
dispersion was measured by Otsuka Electronics Zeta-potential
& Particle size Analyzer ELSZ-2000N. The concentration of
¹1
sample was adjusted to 0.05 mg mL
.
General Procedure for the Deposition of Pt on GO: For
the preparation of Pt/GO composite, 1 g of 3 wt % aq. disper-
sion of GO was suspended in 20 mL of distilled water. To the
GO dispersion was added 20 mL of EtOH at room temperature.
After being stirred at the same temperature for 5 min, PtCl2
(1 mg) was added and stirred vigorously for 5 min, then Et3SiH
was added and stirred for 1 h to obtain Pt/GO dispersion.
Procedure for the Deposition of Ir on GO:
For the
preparation of Ir/GO, 1 g of 3 wt % aq. dispersion of GO was
suspended in 20 mL of distilled water. To the GO dispersion
was added 20 mL of EtOH at room temperature. After being
stirred at the same temperature for 5 min, [Ir(OMe)(cod)]2
(3.0 mg) was added and stirred vigorously for 5 min, then
Et3SiH (300 ¯L) was added and stirred for 1 h to obtain Ir/GO
dispersion.
General Procedure for the Deposition of Pt on other
Carbon Materials: A carbon material (30 mg) was suspended
in 20 mL of distilled water. To the GO dispersion was added
20 mL of EtOH at room temperature. After being stirred at
the same temperature for 5 min, PtCl2 (1 mg) was added and
stirred vigorously for 5 min, then Et3SiH (60 ¯L) was added
and stirred for 1 h.
Procedure for the Deposition of Pd on GO: For the
preparation of Pd/GO, 1 g of 3 wt % aq. dispersion of GO was
suspended in 20 mL of distilled water. To the GO dispersion
was added 20 mL of EtOH at room temperature. After being
stirred at the same temperature for 5 min, PdCl2 or Pd(OAc)2
(1 mg) was added and stirred vigorously for 5 min, then Et3SiH
(450 ¯L) was added and stirred for 1 h.
Procedure for the Deposition of Rh on GO: For the
preparation of Rh/GO, 1 g of 3 wt % aq. dispersion of GO was
suspended in 20 mL of distilled water. To the GO dispersion
was added 20 mL of EtOH at room temperature. After being
stirred at the same temperature for 5 min, RhCl3¢3H2O (3.0
mg) was added and stirred vigorously for 5 min, then Et3SiH
(300 ¯L) was added and stirred for 1 h.
Atomic Force Microscope (AFM) Measurement: AFM
images were taken using a commercial SPM instrument
(Bruker AXS, California, USA, Multimode 8). This AFM has
an extension of pulsed-force mode with improved image and
force resolution, which is named PeakForce-QNM (Quantita-
tive nano-mechanical). In PeakForce-QNM mode, the probe is
vibrated in 2 kHz, and all force curves for entire scanning
pixels are fulfilled. The heights are determined from the force
curves. For sample preparation, dispersions of GO and Pt/GO
(0.01 wt %) were dropped on freshly cleaved mica substrates,
and then dried in air.
Nuclear Magnetic Resonance (NMR) Measurement:
NMR spectra were recorded using a JEOL JNM-LA400 spec-
trometer. Proton chemical shifts are relative to solvent peaks
[chloroform: 7.27 (1H)].
Fourier-Transfer Infrared Measurement:
Fourier-
transfer infrared (FT-IR) was measured using a Shimadzu
AIM-8800 equipped with IR Tracer-100. Each sample was
dried at 50 °C under reduced pressure, and analyzed with ATR
mode.
General Procedure for the Catalytic Oxidation of
Gas Chromatography (GC) Measurement: GC analysis
was performed with a Shimadzu GC-2010 with ZB5 capillary
column, internal diameter 0.53 mm, film thickness 1.50 ¯m,
length 30 m.
X-ray Absorption Fine Structure (XAFS) Measurement:
EXAFS spectra of Pt LIII and Ir LIII edges were measured
at BL-9C station of the KEK-PF (Tsukuba, Japan) with a
Et3SiH:
The Pt/GO dispersion (1.5 mL) was centrifuged
with distilled water, and then with 1,4-dioxane 3 times to
obtain Pt/GO in 1,4-dioxane (1.5 mL). A test tube was charged
with Et3SiH (0.5 mmol), distilled water (5 mmol), and Pt/GO
dispersion in 1,4-dioxane. The reaction mixture was stirred
at room temperature for 1 h. After reaction, ethyl acetate
was added to extract the product. The product yield was deter-
© 2016 The Chemical Society of Japan