Photon Factory Activity Report 2017 #35 (2018)

BL-12C/2017G533, 2015G127

XAFS Characterization of High-Loaded, Size-Regulated Pt Nanoparticles
Prepared from Pt4 Complex and Polymer on Carbon Support
Satoshi MURATSUGU*1, Kentaro ICHIHASHI1, Mizuki TADA1,2
1
2

Department of Chemistry, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8602, Japan.
Research Center for Materials Science (RCMS) & Integrated Research Consortium on Chemical
Science (IRCCS), Nagoya University, Furo, Chikusa, Aichi 464-8602, Japan.

1 Introduction
We succeeded in preparing size-regulated Pt
nanoparticles from carbon-attached Pt tetranuclear (Pt4)complex precursors (Pt loading: maximum 4 wt%) andorganic polymer matrix overlayers and demonstrating thedurability of Pt nanoparticle catalyst on organic reactions(e.g. N-alkylation reaction).[1] We next investigated amethod to prepare size-regulated Pt nanoparticle catalyst
to increase Pt loading for electrocatalyst. A newly
prepared Pt4 complex was polymerized together withpolymer precursor under the presence of multi-walledcarbon nanotubes (MWCNTs), and successive reduction
yielded size-regulated Pt nanoparticles with high Pt
loading. The oxidation states and the local coordination
structures of the Pt4 complex and MWCNT-supported Pt
nanoparticle were investigated by Pt LIII-edge XAFS.

reduced to ca. zero. The white line peak of Pt LIII-edge
XANES of A was decreased, indicated that the Pt
oxidation stare of was reduced to ca. zero, supporting theEXAFS data. Two contributions from Pt-C/O (CN = 0.6 ±0.5, R = 0.205 ± 0.003 nm) and Pt-O/N (CN = 0.5 ± 0.4,R = 0.219 ± 0.003 nm) were observed. TEM image
analyses of A exhibited small Pt nanoparticles of 1.1–1.6
nm with the narrow size distribution (0.3~0.5 nm). The Pt
loading of A was increased to ca. 12 wt. These results
indicate that we succeeded in increasing Pt loading while
keeping the small size of Pt nanoparticles.

2 Experimental
A newly prepared Pt4 complex (1) and a Pt nanoparticle
rsample after reduction (A) were prepared, respectively.
Pt LIII-edge XAFS was measured in a transmission
mode at 20 K at the BL-12C station with a Si(111)
double-crystal monochromator. Ionization chambers
filled with pure N2 and pure Ar were used to monitor
incident and transmitted X-rays, respectively. EXAFS
spectra were analysed using ATHENA and ARTEMIS
programs. k3-Weighted EXAFS oscillations were Fouriertransformed into R-space, and curve-fitting analysis wasperformed in R-space with coordination number (CN),interatomic distance (R), Debye-Waller factor (σ2), andcorrection-of-edge energy (∆E0). Phase shifts andbackscattering amplitudes were calculated by the FEFF8code.
3 Results and Discussion
The local coordination structures of the Pt4 complexand Pt nanoparticles were analyzed by Pt LIII-edge
EXAFS (Figure 1). 1 had Pt-Pt bond at 0.250 ± 0.001 nm(Coordination number (CN): 2.3 ± 0.3) and two Pt-O
bonds at 0.200 ± 0.002 nm (CN: 2.3 ± 0.6) and 0.219 ±0.002 nm (CN: 1.6 ± 0.6), which were very similar to thePt4(CH3COO)8 complex.
The bond distances of the Pt-Pt coordination in A after
the reduction were fitted as 0.275 ± 0.001 (CN = 4.0 ±1.0), whose value was identical to Pt0 foil (R = 0.277 ±0.001). This result indicates that the Pt species wasFigure. 1: k3-Weighted Pt LIII-edge EXAFS Fouriertransforms of 1 and A.
[1] S. Muratsugu, S. Miyamoto, K. Sakamoto, K.
Ichihashi, C.-K. Kim, N. Ishiguro, M. Tada, 2017, 33,10271–10282.
* smuratsugu@chem.nagoya-u.ac.jp