Catalysis Science & Technology
Paper
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H2 and N2 evolution was almost saturated at around 30 and
10 μmol (H2/N2 ratio of 3.0), which corresponded to the
initial amount of NH3 (20 μmol), indicating that NH3 was
almost completely decomposed to H2 and N2 (eqn (2)) over
Au(0.25 × 4)/TiO2(723) under irradiation of visible light.
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2NH3 → N2 + 3H2
(2)
To evaluate the stability of Au/TiO2 in H2 and N2 pro-
duction from NH3, Au(0.25 × 4)/TiO2(723) was used again.
Irradiation of the reaction mixtures under visible light again
induced evolution of H2 and N2, and the formation continued
from 40 h to 80 h without deactivation.
Conclusions
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Gold (Au)-loaded titanium(IV) oxide (Au/TiO2) having both
smaller and larger Au particles was successfully prepared by
the multi-step (MS) photodeposition method. The Au particle
distribution and photoabsorption properties of Au/TiO2 can
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co-existence of large (>10 nm) and small (<5 nm) Au particles
was indispensable for higher activities, which contributed to
strong photoabsorption due to surface plasmon resonance (SPR)
and efficient H2 evolution (proton reduction), respectively.
Au/TiO2 having a bimodal Au distribution can be applied for
the stoichiometric decomposition of ammonia to H2 and
nitrogen under visible light irradiation. On the other hand, in
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oxygen (O2), small Au particles are not requisite because O2 is
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Acknowledgements
This work was partly supported by a Grant-in-Aid for Scientific
Research (no. 23560935) from the Ministry of Education, Culture,
Sports, Science, and Technology (MEXT) of Japan. The authors
(H. K. and A. T.) are grateful for financial support from the
Iketani Science and Technology Foundation. One of the authors
(A. T.) appreciates the Japan Society for the Promotion of
Science (JSPS) for the Research Fellowship for Young Scientists.
Notes and references
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