seem to be the active sites, whereas the presence of small Au particles becomes more
important to show high activity for Au on inert materials and ligand-protected Au
clusters. For dehydrogenation of alcohols under inert atmosphere, the TOF sharply
increased with a decrease in the size of Au, reflecting that the active site would
change to the edge and corner Au atoms. For the alkene oxidation, conflicting results
was reported; Au clusters were important for styrene oxidation but Au NPs larger
than 2 nm were active for cyclohexene oxidation. The difference was explained by
the substrate structure, i.e., allylic oxidation of cyclohexene readily takes place,
which do not need O 2 activation. Atomically precise Au clusters protected by
phosphine or thiolate ligands are one of the hot research topics due to small Au
particle size and narrow size distributions. For cyclohexane oxidation, a unique size
dependence was observed; Au 39 /HAP exhibited the highest catalytic activity among
smaller or larger ones. However, the ligands remained on the Au clusters even after
calcination affected the catalytic properties of Au, which sometimes make difficult to
elucidate the true size effect of Au. For alkane oxidation, the presence of subnanometer-sized Au clusters would be a crucial factor which is probably responsible
for the O 2 activation to form oxygen radical species on the sub-nano Au clusters.
To understand the role of supports and the size effect of Au more precisely for
each reaction will help us to design more efficient and sophisticated Au catalysts. In
order to discuss these effects, the developments of preparation method to deposit Au
as sub-nm clusters with narrow size distributions, new support materials, and of
characterization techniques including in situ measurements are highly demanded.
References
1. Haruta M, Kobayashi T, Sano H, Yamada N (1987) Novel gold catalysts for the oxidation of
carbon monoxide at a temperature far below 0
C. Chem Lett 16:405–408. https://doi.org/10.
1246/cl.1987.405
2. Takei T, Akita T, Nakamura I, Fujitani T, Okumura M, Okazaki K, Huang J, Ishida T, Haruta
M (2012) Heterogeneous catalysis by gold. Adv Catal 55:1–126. https://doi.org/10.1016/
B978-0-12-385516-9.00001-6
3. Okumura M, Fujitani T, Huang J, Ishida T (2015) A career in catalysis: Masatake Haruta. ACS
Catal 5:4699–4707. https://doi.org/10.1021/acscatal.5b01122
4. Ishida T, Koga H, Okumura M, Haruta M (2016) Advances in gold catalysis and understanding the catalytic mechanism. Chem Rec 16:2278–2293. https://doi.org/10.1002/tcr.201600046
5. Haruta M, Yamada N, Kobayashi T, Iijima S (1989) Gold catalysts prepared by coprecipitation
for low-temperature oxidation of hydrogen and of carbon monoxide. J Catal 115:301–309.
https://doi.org/10.1016/0021-9517(89)90034-1
6. Hayashi T, Tanaka K, Haruta M (1998) Selective vapor-phase epoxidation of propylene over
Au/TiO 2 catalysts in the presence of oxygen and hydrogen. J Catal 178:566–575. https://doi.
org/10.1006/jcat.1998.2157
7. Huang J, Akita T, Faye J, Fujitani T, Takei T, Haruta M (2009) Propene epoxidation with
dioxygen catalyzed by gold clusters. Angew Chem Int Ed Engl 48:7862–7866. https://doi.org/
10.1002/anie.200903011
8. Hammer B, Norskov JK (1995) Why gold is the noblest of all the metals. Nature 376:238–240.
https://doi.org/10.1038/376238a0
38
T. Ishida et al.
important to show high activity for Au on inert materials and ligand-protected Au
clusters. For dehydrogenation of alcohols under inert atmosphere, the TOF sharply
increased with a decrease in the size of Au, reflecting that the active site would
change to the edge and corner Au atoms. For the alkene oxidation, conflicting results
was reported; Au clusters were important for styrene oxidation but Au NPs larger
than 2 nm were active for cyclohexene oxidation. The difference was explained by
the substrate structure, i.e., allylic oxidation of cyclohexene readily takes place,
which do not need O 2 activation. Atomically precise Au clusters protected by
phosphine or thiolate ligands are one of the hot research topics due to small Au
particle size and narrow size distributions. For cyclohexane oxidation, a unique size
dependence was observed; Au 39 /HAP exhibited the highest catalytic activity among
smaller or larger ones. However, the ligands remained on the Au clusters even after
calcination affected the catalytic properties of Au, which sometimes make difficult to
elucidate the true size effect of Au. For alkane oxidation, the presence of subnanometer-sized Au clusters would be a crucial factor which is probably responsible
for the O 2 activation to form oxygen radical species on the sub-nano Au clusters.
To understand the role of supports and the size effect of Au more precisely for
each reaction will help us to design more efficient and sophisticated Au catalysts. In
order to discuss these effects, the developments of preparation method to deposit Au
as sub-nm clusters with narrow size distributions, new support materials, and of
characterization techniques including in situ measurements are highly demanded.
References
1. Haruta M, Kobayashi T, Sano H, Yamada N (1987) Novel gold catalysts for the oxidation of
carbon monoxide at a temperature far below 0
C. Chem Lett 16:405–408. https://doi.org/10.
1246/cl.1987.405
2. Takei T, Akita T, Nakamura I, Fujitani T, Okumura M, Okazaki K, Huang J, Ishida T, Haruta
M (2012) Heterogeneous catalysis by gold. Adv Catal 55:1–126. https://doi.org/10.1016/
B978-0-12-385516-9.00001-6
3. Okumura M, Fujitani T, Huang J, Ishida T (2015) A career in catalysis: Masatake Haruta. ACS
Catal 5:4699–4707. https://doi.org/10.1021/acscatal.5b01122
4. Ishida T, Koga H, Okumura M, Haruta M (2016) Advances in gold catalysis and understanding the catalytic mechanism. Chem Rec 16:2278–2293. https://doi.org/10.1002/tcr.201600046
5. Haruta M, Yamada N, Kobayashi T, Iijima S (1989) Gold catalysts prepared by coprecipitation
for low-temperature oxidation of hydrogen and of carbon monoxide. J Catal 115:301–309.
https://doi.org/10.1016/0021-9517(89)90034-1
6. Hayashi T, Tanaka K, Haruta M (1998) Selective vapor-phase epoxidation of propylene over
Au/TiO 2 catalysts in the presence of oxygen and hydrogen. J Catal 178:566–575. https://doi.
org/10.1006/jcat.1998.2157
7. Huang J, Akita T, Faye J, Fujitani T, Takei T, Haruta M (2009) Propene epoxidation with
dioxygen catalyzed by gold clusters. Angew Chem Int Ed Engl 48:7862–7866. https://doi.org/
10.1002/anie.200903011
8. Hammer B, Norskov JK (1995) Why gold is the noblest of all the metals. Nature 376:238–240.
https://doi.org/10.1038/376238a0
38
T. Ishida et al.