3B01
Significantly Enhanced Hydrogen-storage Capacity and Speed in Pd
Nanocrystals Coating with Cu3(BTC)2, BTC = 1,3,5-benzenetricarboxylate)(Grad. Sch. Sci. of Kyoto Univ. 1, JST-CREST2, Grad. Sch. Sci. of Osaka Pref. Univ. 3,
HVEM of Kyushu Univ. 4）○ Guangqin LI1; Hirokazu KOBAYASHI1,2; Hiroshi
KITAGAWA1,2; Yoshiki KUBOTA3; Shoichi TOH4; Tomokazu YAMAMOTO4; Syo
MATSUMURA4[Introduction] Efficient hydrogen storage methods are necessary in order to store thegas more safely, while obtaining a sufficient energy density for power generation fromnext generation devices such as fuel cells.
Palladium (Pd) nanocrystals1 are one
candidate as a hydrogen-storage material
because of a high hydrogen-storage capacity,and the ability to form a stable hydride underambient pressure and temperature. On theother hand, metal-organic frameworks (MOFs)
are porous, organic–inorganic hybrid solids

Fig.1 The structure of HKUST-1

with zeolite-like structures and properties.
MOFs are promising materials for applications in gas storage2, catalyst3 and separation4.
However, MOFs adsorb an insignificant amount of hydrogen at room temperature. Dueto their extraordinarily high surface area and well defined pore structure, MOFs can beused for the stabilization of metal nanoparticles with adjustable size. For example,
HKUST-15 is composed of copper(II) as the metal ion and 1,3,5-benzenetricarboxylate
as the ligand (structure shown in Figure 1).
HKUST-1 can store large amount ofhydrogen at 77 K. It is expected to be a
coating material for hydrogen storage.
In this study, we have synthesized andFig.2 Pd@HKUST-1 coating materialfor hydrogen storagecharacterized Pd nanocrystals coating withHKUST-1 (Pd@HKUST-1). The structure of

Pd@HKUST-1 was shown in Figure 2. Its hydrogen storage properties have been
investigated. Pd@HKUST-1 shows high capacity and rapid speed of hydrogen-storage
property.
[Experiment] Pd@HKUST-1 was synthesized by a liquid-phase method. At first, Pd
nanocrystals were prepared by a reduction of Na2PdCl4 using ascorbic acid. The
mixture of Cu(NO3)2∙3H2O and benzene 1,3,5-tricarboxylic acid in ethanol solution wasstirred at ambient temperature in the presence of the obtained Pd nanocrystals.
[Results and discussion] The powder X-ray diffraction (XRD) pattern of Pd@HKUST1 consisted of two kinds of Pd and HKUST-1 patterns (Fig. 3). Figure 4 shows TEM
image of Pd@HKUST-1. From the TEM image, it was found that the nanofilms wereobserved around the surface of Pd nanocrystals with mean diameter of ca. 10 nm.
STEM-EDS maps demonstrated that the nanofilms include Cu element derived fromHKUST-1. The differences of hydrogen-storage properties between Pd andPd@HKUST-1 have been investigated by hydrogen pressure composition isotherms(PCT). From the PCT result, Pd@HKUST-1 showed rapid and high-capacity hydrogenstorage in Pd nanocrystals covered with metal-organic framework.

Fig. 3 XRPD patterns of samples

Fig. 4 TEM image of Pd@HKUST-1

Reference ：(1) M. Yamauchi et al. J. Phys. Chem. C, 2008, 112, 3294. (2) L. J. Murray et al. Chem. Soc. Rev. 2009,38, 1294–1314. (3) J. Lee et al. Chem. Soc. Rev. 2009, 38, 1450–1459. (4) E. D. Bloch et al. Science
2012, 30, 1606–1610. (5) S. S. Y. Chui et al. Science 1999, 283, 1148-1150.