Paper
RSC Advances
9
Y. Sekine, M. Haraguchi, M. Matsukata and E. Kikuchi,
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5. Conclusions
Methane steam reforming was conducted with and without an 10 S. Ogo and Y. Sekine, Chem. Rec., 2017, 17, 726–738.
electric eld over Pd catalysts loaded on various oxides 11 M. Torimoto, K. Murakami and Y. Sekine, Bull. Chem. Soc.
including CeO
2
, Nb
2
O
5
, and Ta
2
O
5
to elucidate the factors
Jpn., 2019, 92, 1785–1792.
controlling activity of the catalyst support. These catalysts 12 M. Torimoto, S. Ogo, D. Harjowinoto, T. Higo, J. G. Seo,
showed almost identical and low activity by heated catalysis.
Therefore, the structure of supported metal has almost identical
S. Furukawa and Y. Sekine, Chem. Commun., 2019, 55,
6693–6695.
structure (i.e. particle diameter, dispersion). Results of activity 13 Y. Sekine, M. Haraguchi, M. Tomioka, M. Matsukata and
tests conducted with the electric eld demonstrated that all
E. Kikuchi, J. Phys. Chem. A, 2010, 114, 3824–3833.
catalysts showed activity at low temperatures exceeding the 14 T. Kumagai, A. Shiotari, H. Okuyama, S. Hatta, T. Aruga,
thermal equilibrium. The order of activity was Pd/CeO
2
> Pd/
I. Hamada, T. Frederiksen and H. Ueba, Nat. Mater., 2012,
11, 167–172.
Nb > Pd/Ta . Electrochemical impedance spectroscopy
2
O
5
2 5
O
(
EIS) measurements under dry and wet conditions were con- 15 T. Norby, MRS Bull., 2009, 34, 923–928.
ducted to evaluate the surface proton conduction. The order of 16 N. Agmon, Chem. Phys. Lett., 1995, 244, 456–462.
proton transport ability was CeO > Nb O > Ta O , indicating 17 Z. Zuo, Y. Fu and A. Manthiram, Polymers, 2012, 4, 1627–
2
2
5
2 5
that H O adsorption and activation properties over these oxide
1644.
supports differ. Finally, transmittance FT-IR measurements of 18 K. N. Manukumar, B. Kishore, K. Manjunath and
the adsorbed pyridine species on these oxide supports were
G. Nagaraju, Int. J. Hydrogen Energy, 2018, 43, 18125–18135.
measured to evaluate the Lewis acid amount. By introducing 19 R. Manabe, S. Ø. Stub, T. Norby and Y. Sekine, Solid State
O before measurements, the Lewis acid amount decreased,
Commun., 2018, 270, 45–49.
indicating that OH groups formed on a Lewis acid (metal 20 S. Ø. Stub, K. Thorshaug, P. M. Rørvik, T. Norby and
2
H
2
cation). The order of the amount of formed OH groups was
CeO > Nb O > Ta O . The results obtained for EIS and IR
E. Vøllestad, Phys. Chem. Chem. Phys., 2018, 20, 15653–
15660.
2
2
5
2 5
revealed that the dissociative adsorption property of H O and 21 S. Ø. Stub, E. Vøllestad and T. Norby, J. Phys. Chem. C, 2017,
2
the amount of formed OH groups are related strongly to the
proton hopping ability. To summarize this work, as the adsor- 22 B. Scherrer, M. V. F. Schlupp, D. Stender, J. Martynczuk,
121, 12817–12825.
bed and activated amounts of H
2
O become larger, the proton
J. G. Grolig, H. Ma, P. Kocher, T. Lippert, M. Prestat and
conductivity becomes higher, then the catalyst was able to
L. J. Gauckler, Adv. Funct. Mater., 2013, 23, 1957–1964.
achieve high activity in the electric eld for low-temperature 23 S. Miyoshi, Y. Akao, N. Kuwata, J. Kawamura, Y. Oyama,
MSR.
T. Yagi and S. Yamaguchi, Chem. Mater., 2014, 26, 5194–
200.
5
2
4 I. G. Tredici, F. Maglia, C. Ferrara, P. Mustarelli and
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Conflicts of interest
5
146.
5 S. Raz, K. Sasaki, J. Maier and I. Riess, Solid State Ionics,
001, 143, 181–204.
There are no conicts to declare.
2
2
Acknowledgements
26 Y. Hisai, K. Murakami, Y. Kamite, Q. Ma, E. Vøllestad,
R. Manabe, T. Matsuda, S. Ogo, T. Norby and Y. Sekine,
Chem. Commun., 2020, 56, 2699–2702.
This work was supported by JST CREST JPMJCR1423, Japan.
2
7 K. Murakami, Y. Tanaka, R. Sakai, Y. Hisai, S. Hayashi,
Y. Mizutani, T. Higo, S. Ogo, J.-G. Seo, H. Tsuneki and
Y. Sekine, Chem. Commun., 2020, 56, 3365–3368.
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