Production of hydrogen peroxide by combination of semiconductor-photocatalysed oxidation of water and photocatalytic two-electron reduction of dioxygen

Article abstract of DOI:10.1039/c6ra06814f

The production of hydrogen peroxide from water and dioxygen was achieved by combination of semiconductor-photocatalysed oxidation of water and photocatalytic two-electron reduction of dioxygen with [Ru^II((MeO)₂bpy)₃]²

Full text of DOI:10.1039/c6ra06814f

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Production of hydrogen peroxide by combination
of semiconductor-photocatalysed oxidation of
water and photocatalytic two-electron reduction
of dioxygen†
Cite this: RSC Adv., 2016, 6, 42041
Received 15th March 2016
Accepted 19th April 2016
a
b
a
c
Yusuke Isaka, Yusuke Yamada,* Tomoyoshi Suenobu, Tatsuo Nakagawa
DOI: 10.1039/c6ra06814f
de
and Shunichi Fukuzumi*
www.rsc.org/advances
The production of hydrogen peroxide from water and dioxygen was
We have previously reported that H O can be produced by
2
2
achieved by combination of semiconductor-photocatalysed oxidation combination of thermal water oxidation using water oxidation
of water and photocatalytic two-electron reduction of dioxygen with catalysts and photocatalytic two-electron reduction of O using
2
II
2+
0
0
14–16
[
Ru ((MeO)
2 3
bpy) ]
((MeO)
2
bpy ¼ 4,4 -dimethoxy-2,2 -bipyridine) in Ru complexes as photocatalysts.
and O reduction were performed in parallel in a reaction
vessel, produced H could be decomposed in the presence of
When the water oxidation
3+
the presence of Sc in water under visible light irradiation.
2
2 2
O
water oxidation catalysts to preclude the production of H
higher concentrations.
2 2
O at
2 2
Hydrogen peroxide (H O ) has attracted considerable interest as
a green fuel that can be used in one-compartment fuel cells free
of expensive membranes with theoretical maximum output
potential of 1.09 V, which is comparable to that of a hydrogen
We report herein the photocatalytic production of H O from
2
2
H O and O using a two-compartment cell composed of
2
2
a semiconductor photocatalyst anode in one cell and a carbon
1–7
fuel cell (1.23 V).
H
2
O
2
has also merited increasing attention
3+
cloth cathode in the presence of Ru complexes and Sc in an
as a green oxidant, because only water is produced as the
2
O -saturated aqueous solution in the other cell to achieve
8–11
reduced product.
H O is currently produced by an industrial process
2 2
higher concentrations of H O as compared with those with
2
2
a one-compartment cell.
composed of sequential hydrogenation and oxidation of an
alkyl anthraquinone, which is not environmentally benign
because of many reasons, such as utilisation of toxic solvents,
consumption of large amounts of energy, and requirement for
A schematic representation of the two-compartment cell
employed in this study is shown in Fig. S1,† where WO3 or
17
BiVO was used as a photoanode for photooxidation of water
4
and a carbon mesh cathode was used for photoreduction of O2
by Ru complexes. The two compartments were separated by
a Naon membrane.
12,13
multiple reaction steps.
2 2
It is highly desired to produce H O
from water and dioxygen in the air using solar energy.
II
2+
0
0
When [Ru ((MeO)
2
bpy)
3
]
((MeO)
2
bpy ¼ 4,4 -dimethoxy-2,2 -
bipyridine, 1) was employed as a photocatalyst for two-electron
reduction of O in the presence of Sc (100 mM) in an O -satu-
2 2
3+
a
Department of Material and Life Science, Graduate School of Engineering, Osaka
University, ALCA, Japan Science and Technology Agency (JST), Suita, Osaka
rated aqueous solution, photocurrent generation was observed as
shown in Fig. 1a, where no or little photocurrent was observed in
5
65-0871, Japan
1
8
II
2+
the absence of O . When [Ru ((MeO) bpy) ] was replaced by
b
2
2+
2
3
Department of Applied Chemistry and Bioengineering, Graduate School of
Engineering, Osaka City University, Osaka 558-8585, Japan. E-mail: ymd@a-chem.
eng.osaka-cu.ac.jp
II
[
Ru (Me
2
3
phen) ]
(Me
2
phen ¼ 4,7-dimethyl-1,10-phenathroline,
2) under otherwise the same conditions, the photocurrent was
signicantly smaller by two orders of magnitude (Fig. 1b).
When monochromic light (l ¼ 450 nm) was continuously
irradiated to acidic aqueous solutions of 1 and 2, formation of
c
Unisoku Co., Ltd, Kasugano 2-4-3, Hirakata, Osaka 573-0131, Japan
d
Department of Chemistry and Nano Science, Ewha Womans University, Seoul 120-
7
50, Korea
e
Faculty of Science and Technology, Meijo University, ALCA, Japan Science and
Technology Agency (JST), Nagoya, Aichi 468-8502, Japan. E-mail: fukuzumi@chem.
eng.osaka-u.ac.jp
III
corresponding Ru complexes was conrmed for both solutions
by UV-Vis measurements (Fig. 2 and S2†). While over 90% of 1
III
3+
originally present in the solution existed as [Ru ((MeO) bpy) ]
†
Electronic supplementary information (ESI) available: Experimental details, 5
2
3

gures [UV-Vis absorption spectra of solutions and the electrode, schematic aer 3500 s of photoirradiation, only 22% of 2 was observed as
III
3+
representation of a two-compartment cell, phosphorescence spectrum, time [Ru (Me
phen)
]
aer light irradiation (Fig. S3†). Thus the
2
3
course of photocurrent and oxygen generation], estimation of the O amount,
2
increased photocurrent observed for 1 as compared to 2 was due to
and calculation of the simulated spectrum. See DOI: 10.1039/c6ra06814f
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Fig. 1 Photocurrent (at 0.30 V vs. SCE) under photoirradiation by a Xe
II
2+
lamp (l > 420 nm) of (a) [Ru ((MeO)
2
bpy)
3
]
(160 mM) or (b)
-saturated (blue
II
2+
[
2 3
Ru (Me phen) ]
(160 mM) in an O
lines) aqueous solution (8.0 mL) of Sc (100 mM).
2
- (red lines) or N
2
3+
II
2+
Fig. 3 (a) Transient absorption spectra of [Ru ((MeO)
in an O -saturated H
profiles of bleaching at 500 nm due to [Ru ((MeO)
2
3
bpy) ]
(20 mM)
2
2
O after laser excitation at l ¼ 355 nm. (b) Time
III 3+
2
bpy)
3
]
in the
3+
absence (black line) and presence (blue line) of Sc (75 mM).
Fig. 2 Changes in the UV-Vis absorption spectrum of an aqueous
Fig. 4 (a) Photocurrent (at 0.25 V vs. SCE) under photoirradiation of
II
2+
II
2+
solution of (a) [Ru ((MeO)
2
bpy)
3
]
(40 mM) and (b) [Ru (Me
2
phen)
3
]
3+
BiVO
420 nm). (b) O
applied potential of 0.52 V vs. SCE measured by using an O
4
anode in an aqueous solution of Sc (100 mM) with a Xe lamp (l
evolution during photocurrent generation at an
sensor.
3+
(
40 mM) containing Sc (100 mM) under photoirradiation by mono-
>
2
III
chromic light (l ¼ 450 nm). Absorption spectrum of (a) [Ru ((MeO)
2
-
3+
III
3+
3+
2
3
bpy) ]
(40 mM) and (b) [Ru (Me
2
3
phen) ]
in the presence of Sc
(
100 mM) in water are also shown in the figures (orange lines). pH of
the aqueous solutions are adjusted to 1.0 by adding aq. H
the samples.
2 4
SO for all of
BiVO
4 3 2
was replaced by WO , the rate of O evolution became
signicantly reduced (Fig. 4b and S5†).
Formation of holes in the photoexcited BiVO was observed
4
III
19
increased concentration of Ru species in situ that can oxidise the by absorption around l ¼ 600 nm as reported previously with
electrode to generate photocurrent.
a new technique for subnanosecond transient absorption
measurement, RIPT (Randomly-Interleaved-Pulse-Train)
s ) was comparable to that from method (Fig. 5). The lifetime of an observed hole was elon-
II
The rate constant of electron transfer from [Ru ((MeO)
2
-
2
+
9
ꢁ1 ꢁ1
20
bpy)
[
3
] * to O
2
(4.9 ꢀ 10 M
II
2+
9
ꢁ1
ꢁ1
Ru (Me
2
phen)
3
] * (6.1 ꢀ 10
M
s ) where asterisk gated when a positive voltage was applied to the electrode
possibly because recombination of electrons and holes was
In the presence of Sc (100 mM), back electron transfer from retarded by accelerated consumption of electrons at the elec-
1
4
indicating the photoexcited states of the complexes (Fig. S4†).
3
+
ꢁ
III
3+
O c to [Ru ((MeO) bpy) ] examined by nanosecond laser trode (Fig. 5b).
2
2
3

ash photolysis measurements was decelerated signicantly
4
The combination of the BiVO photoanode and carbon mesh
cathode in the presence of [Ru ((MeO) bpy) ] and Sc gave
2 3
3
+
ꢁ
18
II
2+
3+
due to the strong binding of Sc to O
2
c
as shown in Fig. 3.
When BiVO was employed as photocatalyst for the photo- the best performance in terms of the photocatalytic production
4
oxidation of water under visible light irradiation, photocurrent of H O from H O and O as shown in Fig. 6.
2
2
2
2
2
generation as well as O evolution was observed (Fig. 4). When
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Scheme 1 Catalytic cycle of the photocatalytic production of H
from H O and O using a Ru photocatalyst and a semiconductor
photocatalyst. Ru * and O
complex and superoxide radical anion, respectively.
2 2
O
2
2
II
ꢁ
II
2
c denotes the photoexcited state of Ru
III
4 2
Electrons in conduction band of BiVO reduce [Ru ((MeO) -
3
+
II
2+
bpy)
In conclusion, H
by combination of BiVO
photocatalytic two-electron reduction of dioxygen with
3
]
to regenerate [Ru ((MeO)
was produced from water and dioxygen
-photocatalysed oxidation of water and
2 3
bpy) ] .
2 2
O
4
II
2+
3+
[
Ru ((MeO) bpy) ] in the presence of Sc in water using
2 3
4
Fig. 5 (a) Transient absorption spectra of photoexcited BiVO . (b)
a two-compartment cell under visible light irradiation. This
Absorbance at l ¼ 700 nm relative to absorbance at 0 ms without bias
study provides a promising way for production of H O2 as
2
voltage (blue line) and at 0.5 V vs. SCE (red line).
a solar fuel. The further improvement of the catalytic activity
and stability is now in progress.
Acknowledgements
This work was supported by ALCA and SENTAN (Development
of Systems and Technology for Advanced Measurement and
Analysis) programs of Japan Science and Technology Agency
(JST), Japan and JSPS KAKENHI (Nos 24350069 and 15K14223 to
Y. Y.). We thank Mr Kido Okamoto, Unisoku Co., Ltd., for the
setup of the RIPT instrument with our electrodes.
Notes and references
Fig.
compartment cell composed of a semiconductor photocatalyst anode
BiVO (green line and blue line) or WO (red line)) in one cell and
a carbon cloth cathode in the presence of [Ru ((MeO)
2 2
6 Production of H O under photoirradiation of a two-
1
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4
3
II
2+
2 3
bpy) ]
(160
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2+
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Based on above-mentioned results, the photocatalytic
production of H
2
O
2
from H
2
O and O
2
is summarised in Scheme
II
2+
1
. Electron transfer from [Ru ((MeO)
2
ꢁ
bpy)
3
] * to O
2
occurs to
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III
3+
3+
produce [Ru ((MeO)
to O
2
ꢁ
bpy)
3
]
and O
2
c . Strong binding of Sc
ꢁ
3+
2
c
to give O c –Sc complex prohibits back electron
2
ꢁ
3+
III
3+
transfer from the O
2
c –Sc complex to [Ru ((MeO)
2
bpy)
3
] .
ꢁ
3+
+
The O c –Sc complex disproportionates in the presence of H
2
to produce H O . On the other hand, the photoexcitation of
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4
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