ChemCatChem
10.1002/cctc.201901128
FULL PAPER
air intrusion during sampling. In the absence of H
2
, the samples
Autoclave experiments
2
For the autoclave experiments 2 mg of Pd, or 2.33 g of ZrO were
were purged throughout the experiment using N
2
.
suspended in 100 ml 20 mM Tris. As for the previous experiments
the pH was adjusted to 7.5 with HCl before the reaction vessel was
transferred into an aerated autoclave. The autoclave was then
Table 2. Overview of gases used during the experiments
pressurized with H
0 bar H . Throughout the experiments the powder suspensions
were stirred with a paddle stirrer to avoid sedimentation. Samples
2 2
to give final partial pressures of 0.2 bar O and
H
2
partial pressure / %
H
2
partial pressure / bar
Purity / %
4
2
1
5
0
0
0
00
1.01
≥ 99.995
were taken during two weeks and the concentrations of H
2
O
2
as well
-
-
-
2
3
4
5.1 x 10
5.1 x 10
5.1 x 10
0.00
as OH were monitored.
.5
.05
(100 % N
2
)
≥ 99.999
Acknowledgements
The Swedish Nuclear and Fuel Waste Management Company
SKB) is gratefully acknowledged for financial support.
(
Uranyl reduction by H
To measure the kinetics of UO
partial pressure below 1 bar, different gas mixtures were used (table
2
2
+
2
reduction depending on the H
2
Keywords: ε-particles • heterogeneous catalysis • hydrogen •
-
2
3
). 8 mg of Pd were suspended in HCO solution and the mixture
palladium • spent nuclear fuel
was deoxygenized through purging for 30 min in the custom made
setup as described above. The gas flow was kept constant at 0.9 l
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-
1
min and the sample was stirred using a magnetic stirrer throughout
up to 2050, IAEA-RDS-1/38, 2018.
the experiment.
After the 30 min equilibration time, 0.56 ml 5 mM uranyl nitrate were
[
2]
B. Faybishenko, J. Birkholzer, D. Sassani, P. Swift, Eds.,
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injected into the reaction vessel through the septum using
hypodermic needle to reach a total volume of 280 ml, a HCO
a
-
3
concentration of 2 mM and a uranyl concentration of 0.01 mM. U(VI)
concentrations were measured over time.
[
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H
2
O
2
reactivity as a function of the H
To determine the reactivity of H
concentrations were measured over time as a function of H
2
partial pressure
towards H on Pd, H
partial
2
O
2
2
2 2
O
2
J. W. T. Spinks, R. J. Woods, An Introduction to Radiation Chemistry,
pressure below 1 bar. 8 mg of Pd powder were suspended in water
and the mixture was left to deoxygenize through purging for 30 min.
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After this equilibration time H
into the reaction vessel using a hypodermic needle to a total volume
of 280 ml and a H concentration of 0.22 mM. The gas flow was
kept constant at 0.9 l min and the sample was stirred using a
2 2
O was injected through the septum
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O
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-
1
magnetic stirrer throughout the experiment.
were measured over time.
H
2
O
2
concentrations
[
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Catalytic decomposition of H O
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For experiments where the production of surface bound OH was
measured simultaneously to H
powder were added to a 20 mM tris solution and the pH was
adjusted to 7.5 using HCl. The mixture was purged with N to
deoxygenize for 30 min and H was added to a concentration of 5
mM and a total volume of 25 ml. As a comparison to the Pd case,
the same experiment was performed using 63 mg of ZrO powder
instead of Pd. The background consumption of was
determined in the absence of any powder. All samples were stirred
using a magnetic stirrer, purged with N and protected from light
as well as CH O concentrations
2 2
O decomposition, 30 mg of Pd
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2
2
O
2
[
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2 2
H O
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throughout the experiment.
were measured over time.
H
2
O
2
2
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