Hierarchical CdS nanostructure by Lawesson's reagent and its enhanced photocatalytic hydrogen production

Article abstract of DOI:10.1039/c4ra15138k

Lawesson's reagent (LR) has been effectively exploited for the synthesis of hierarchical architectures of cadmium sulphide (CdS) nanostructures for the first time. The X-ray diffractograms of the as synthesised CdS nanostructures confirm the formation of hexagonal CdS. The broadness of the XRD peaks clearly indicates the nanocrystalline nature of CdS with average crystallite size of 4 nm. A FESEM study revealed the formation of hierarchical nanostructures, whereas a TEM study showed that the hierarchical arrangement is composed of nanosized CdS particles. A band-gap i.e. 2.4 eV was derived from diffuse reflectance spectroscopy. The photoluminescence spectrum showed an emission peak at 535 and 568 nm which can be attributed to band-edge emission and surface emissions or possible metal vacancies, respectively. Considering the band-gap within the visible region, the photocatalytic hydrogen evolution performance of these CdS nanostructures was performed under visible light irradiation from hydrogen sulphide and water, respectively. Utmost hydrogen evolution i.e. 14136 μmol h^-1 g^-1 and 2065 μmol h^-1 g^-1 was observed over a naked CdS nanostructure via H₂S and water decomposition, respectively. The amount of hydrogen obtained by H₂S splitting is much higher as compared to earlier reports. This journal is

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Journal Name
RSCPublishing
ARTICLE
Hierarchical CdS Nanostructure by Lawesson’s
Reagent and its Enhanced Photocatalytic Hydrogen
Production
Cite this: DOI: 10.1039/x0xx00000x
Received 00th January 2012,
Accepted 00th January 2012
a
a
a
Vikram U. Pandit, Sudhir S. Arbuj, Ranjit R. Hawaldar, Pradnya V.
a
b
a
Kshirsagar, Amarsinh J. Deshmukh, Jalindar D. Ambekar, Uttam P.
Mulik, Suresh W. Gosavi, Bharat B. Kale*
DOI: 10.1039/x0xx00000x
a
c
a
www.rsc.org/
Lawesson’s reagent (LR) has been effectively exploited for the synthesis of hierarchical
architectures of Cadmium sulphide (CdS) nanostructures for the first time. The X-ray
diffractograms of the as synthesised CdS nanostructures confirms the formation of hexagonal
CdS. The broadness of XRD peaks clearly indicates the nanocrystalline nature of CdS with
average crystallite size of
4 nm. FESEM study revealed the formation of hierarchical
nanostructures, whereas TEM study showed that the hierarchical arrangement is composed of
with nanosized CdS particles. A band-gap i.e. 2.4eV was derived from diffuse reflectance
spectrum. Photoluminescence spectrum showed emission peak at 535 and 568 nm which can be
attributed to band-edge emission and surface emissions or possible metal vacancies,
respectively. Considering the band-gap within visible region, the photocatalytic hydrogen
evolution performance of these CdS nanostructures was performed under visible light irradiation
fromhydrogen sulphide and water, respectively. Utmost hydrogen evolution i.e.14,136
and 2,065 mol/h/g were observed over a naked CdS nanostructure via H S and water
S splitting is much higher
ꢀmol/h/g
ꢀ
2
decomposition, respectively. The amount of hydrogen obtained by H
as compared to earlier reports.
2
1
2
1
. Introduction
lithography. Hence, a lot of efforts have been concentred to
study the effect of manipulation of size, shape and crystal
Over the last few decades, nanostructured materials have been
at the centre of attention owing to their fascinating sizeꢀ
dependent optical, electronic, thermal, mechanical, chemical,
and physical properties. These nanomaterial display unique
properties not only from their bulk counterparts but also from
those of the atomic or molecular precursors from which they
are synthesized. For the fabrication of nextꢀgeneration
optoelectronic devices and for fulfilling the energy demand the
13
structure of CdS materials on their optoelectronic properties.
Studies have also been devoted for the synthesis and
characterization of various nanostructures, such as nanotubes,
nanowires, nanorods, and nanobelts.
1
ꢀ3
14ꢀ15
The ideal bandꢀgap of
CdS in bulk as well as nano form makes it an attractive
semiconductor for photocatalytic applications like Hydrogen
sulphide (H S) and water splitting. A large quantity of H S is
2
2
produced in oil refineries which possess
environmental threat. Once produced, it remains for many years
in environment thereby causing pollution. Till date, only few
techniques have been effectively used for treating this H S. Of
all the H S produced globally, a negligible amount is utilized to
produce sulphur by Claus process for agricultural and
pharmaceutical industries.
as it produces large amount of waste and is also energy
intensive. Oil refineries or natural gas extraction satisfy the
basic demand for fuel of the uncontrollably growing global
a
serious
4
ꢀ
use of nanoscale semiconductor nanostructures is imperative.
5
Oflate, lasers, sensors and field emitters using nanomaterial
have been demonstrated by many researchers. Instead of all the
efforts till date, there exists a quest to find better, cheaper and
16
2
2
6
ꢀ7
efficient nanomaterial.
In this context, cadmium sulphide with a band gap 2.4 eV is a
promising candidate owing to its wide ranging applications in
nonlinear optical devices, flatꢀpanel displays, lightꢀemitting
diodes, lasers,
17ꢀ19
This process is not ecoꢀfriendly
8
9
10ꢀ11
logic gates, and transistors, wide application
in telecommunications, data storage, and nearꢀfield optical
This journal is © The Royal Society of Chemistry 2013
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population and hence their operations cannot be terminated. Cadmium sulphide nanostructures thus synthesized were
Therefore, there is an immediate demand to convert characterized by Xꢀray diffraction (ModelꢀD8, Advance,
environmentally hazardous side products like H S into viable Bruker AXS). The samples were also characterized with field
2
2
0ꢀ21
fuel sources like H2.
emission scanning electron microscope (FESEM) and
Hydrogen is an ideal fuel for future owing to its clean and transmission electron microscopy (TEM, model Philips, EMꢀ
renewable nature. Hydrogen can be produced by gasification CMꢀ12) to determine the morphology and particle size
from biomass, methane reforming, through the electrolysis of respectively. The optical properties were recorded using UVꢀ
1
6,22ꢀ23
H O or H S and photocatalytic cleavage of H S or H O.
visibleꢀnear infrared (UVꢀVisꢀNIR) spectrophotometer (Perkin
2
2
2
2
Of all the processes, the photocatalytic processes using solar Elmer lambdaꢀ950 spectrometer). Photoluminescence spectra
energy for hydrogen production seems to be the most were recorded by the photoluminescence spectrometer Perkinꢀ
environmentally safe and less energy intensive methodology as ElmerꢀLSꢀ55. The formation of side products during the
1
solar energy is free of cost and abundantly available.
reaction was confirmed by H NMR (VarianꢀNMRꢀMercury
Among all the available catalysts, CdS is a promising 300). The quantification of H and O was carried out using Gas
2
2
photocatalyst for H S as well as H O splitting due to suitable Chromatograph (Model Shimadzu GCꢀ14B, MSꢀ5 Å column,
2
2
position of the conduction band edge that is more negative than TCD, Ar carrier).
+
27
the reduction potential of H /H . Many approaches for
2
2
.3. Photocatalytic activity measurement
improving the hydrogen production rate and photoꢀstability of
the photocatalyst have been investigated/are under
2
.3.1. PHOTOCATALYTIC H2S SPLITTING
2
8
investigation. For example, CdS loaded with MoS coꢀloaded
2
The Hydrogen evolution was performed in a quartz photo
reactor using 0.1 g CdS with the help of a Xeꢀ lamp light source
(Oriel) of intensity 450W.
was filled with 250 mL, 0.25 M aqueous KOH and purged with
argon for 30 min. Hydrogen sulphide (H S) was bubbled
through the solution for 60 min. at the rate of 2.5 mL min .
Photocatalyst (CdS) was introduced in to the reactor and
irradiated with the visibleꢀlight source at a constant stirring
with continuous H S bubbling (2.5 mL/min). The excess H S
was trapped in (0.5 M) NaOH solution. The amount of evolved
H was measured using graduated gas burette and analyzed
with Pt and PdS, incorporation of CdS particles into the
mesopores of TiꢀMCMꢀ41 and introduction of graphene
1
9ꢀ20
2
9ꢀ32
The cylindrical quartz reactor
nanosheets into CdS have been used.
In general, there are
different factors that control the H production rate on CdS
2
2
photocatalyst, such as morphology, particle size, phase
ꢀ
1
3
3ꢀ37
structure and crystalline nature.
A variety of approaches
have been proposed to enhance the photocatalytic activity of
CdS photocatalyst, including the synthesis of CdS nano
material’s with various morphologies (nanowires, nanorods,
2
2
3
8ꢀ46
nanospheres, nanosheets etc.) and quantumꢀsized CdS.
In
2
spite of recent advances in synthesis of nanomaterial, the
production of CdS nanostructures still requires an expensive
template and harsh conditions, which limit largeꢀscale
using Gas Chromatograph (Model Shimadzu GCꢀ14B, MSꢀ5 Å
column, TCD, Ar carrier). The schematic of H S splitting setup
is depicted in supporting information (Fig. S1).
2
47ꢀ49
production or commercialization of the process.
With all these clues in mind and our experience
1
7ꢀ25
in H2S
2
.3.2. PHOTOCATALYTIC HYDROGEN GENERATION FROM WATER
splitting for H production using UVꢀvisible light, we decided
2
Photocatalytic hydrogen generation experiments were conducted
in a two neck 250 mL borosilicate round bottom flask. In a
typical run, 0.1 g of catalyst (containing 0.5 wt% Pt loading)
was suspended in an aqueous solution and irradiated under a
to explore the efficacy of ultraꢀsmall CdS nanostructures
produced by using an inexpensive and simple procedure with
Lawesson’s reagent as a sulphur source for visibleꢀlight driven
photocatalytic hydrogen generation from H S and H O.The
formation mechanism and optical properties have also been
discussed.
2
2
4
00 W high pressure mercury vapour lamp with continuous
stirring. In this study, we used three types of
scavengers/sacrificial reagents viz. methanol, Na S and Na SO
3
2
2
as well as benzyl alcohol. The Ptꢀloaded CdS photocatalysts
were prepared by a photochemical deposition method. For this
purpose, powder photocatalyst was stirred in a 25% methanol
aqueous solution containing H PtCl and irradiated under Hg
2
. Experimental
2
.1.Synthesis of CdS flowers
2
6
In a dry 100 ml beaker, 2g of cadmium nitrate was dissolved in
small amount of water and in another 100ml beaker 0.70 g of
Lawesson’s reagent (97%, Spectrochem) was dissolved in
chloroform. Both the solutions were transferred to150 ml teflon
coated hydrothermal reactor and kept for 90ºC for 15 h. The
yellow solids are filtered and washed with water and copious
amount of chloroform to remove unreacted starting materials.
5
0
lamp for 4 h. The mercury vapour lamp was kept vertically in
the quartz tube, provided with a water circulation arrangement
in order to minimize the heating effect due to IR radiation. The
evolved gases were collected in a eudiometer tube having a
septum arrangement to remove the gas for GC analysis. Prior to
each photocatalytic experiment; the reaction mixture was
purged with ultra pure grade Argon gas for 15 min to flush out
dissolved gases in the reaction mixture. The eudiometer tube is
filled with a saturated solution of NaCl to avoid the dissolution
of evolved gas.
2
.2 Characterization:
2
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3
. Results and Discussion
To investigate the morphology of the as prepared
CdSnanopowders at macroscopic scale, FESEM study was
performed. Fig 2a&b shows FESEM images of the CdS sample
prepared at 10h. The magnified image (Fig. 2, b) clearly shows
porous nanostructure with arrangement of thin nanosheets
having petal like structures. Fig. 2 c and d shows FESEM
images of CdS prepared at 15h, where magnified image shows
twin puffy flowers having elongated spikes with pointed tips.
The spike arranged in circular fashion, originating from the
centre.The sizes of these flowers are in the range of 3ꢀ5 µm.
3
.1. Materials characterization
3
.1.1. XꢀRAY ANALYSIS
The XRD pattern of the asꢀsynthesized CdS at 10 and 15 h are
depicted in Fig. 1. The product prepared at 10 h of reaction time
shows broad and noisy peaks indicating amorphous nature of
product. However, the reflection peak position(s) validates the
formation of hexagonal CdS.
3
.1.3. TEM ANALYSIS
TEM images for as prepared CdS nanostructures along with
selected area diffraction pattern (SAED) are shown in Fig. 3.
From the TEM images, it can be seen that the flowers are
formed via selfꢀassembling of very thin nanopetals which are
1
7
created by selfꢀalignment of 5 to 10 nm CdS nanoparticles.
The petals are curving in nature which was also seen in
FESEM. Few more TEM images are provided in supporting
information (Fig. S2). TEM images (S2) clearly shows the petal
surface with the tiny nanoparticles. The Concentric fused rings
can be observed in the SAED pattern and matches with the
hexagonal phase of CdS thereby supporting XRD analysis
(
inset of Fig. 3 b).
Fig.1. XRD pattern of Cadmium Sulphide nanostructures
Furthermore, to obtain wellꢀdefined crystalline CdS, the
reaction was performed at 15 h. Xꢀray powder diffraction
(
=
XRD) pattern (Fig. 1) for this sample displays peaks at 2θ
24.8 , 26 , 27.8 , 44 , and 52.5 corresponding to (100), (002),
º
º
º
º
º
(
101), (110) and (112) crystal planes of hexagonal CdS (JCPDS
No.41ꢀ1049), respectively. The broad XRD peaks indicate the
formation of nanoꢀstructured CdS. The average crystallite size
calculated using Scherrer’s formula is found to be 4 nm.
Fig. 3.TEM micrograph of CdS nanoparticles and SAED image (inset of Fig. 3b).
3
.1.2. MORPHOLOGICAL STUDY BY FEꢀSEM
3
.1.4. UVꢀVIS SPECTROPHOTOMETRY
Fig.2. FESEM images of Cadmium sulphide nanostructure (a, b) 10h and c, d) 15h)
This journal is © The Royal Society of Chemistry 2012
Fig.4. DRS spectra of Cadmium sulphide nanostructures
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The optical properties of as prepared CdS nanopowders were (B) with wellꢀknown mechanism (See supporting information
5
2ꢀ54
studied
using
UVꢀvisible
spectrophotometer
and scheme S1).
The monomer (B) forms a complex with
photoluminescence spectrometry. Fig.
4
depicts diffuse cadmium as shown in the scheme 1. Further, this complex upon
reflectance spectra of as prepared CdS nanoflowers. The band decomposition under hydrothermal conditions forms cadmium
edge was observed at around 530 nm which corresponds to the sulphide and side products A and unreacted starting monomer
band gap of 2.4 eV. The absorbance maxima observed to be B. The as formed CdS using Lawesson’s reagent was
around 450 nm indicating the blue shift in the absorbance exclusively characterized by XRD and TEM described above.
1
7ꢀ18,51
maxima depicts the formation of nanoꢀsized CdS.
The side products A and B formed in this reaction was analysed
and confirmed by using H NMR (supporting information S3
1
3
.1.5. PHOTOLUMINESCENCE SPECTRA
and S4 respectively) and Mass spectroscopy. Both the side
1
products are having nearly same H NMR spectrum but only in
case of the A, the aromatic protons are slightly more deshielded
than the B due to electro negativity of oxygen which can be
clearly seen in the schematic of the mechanism (scheme1).The
replacement of sulphur by the oxygen from monomer B is a
further evidence for the formation of cadmium sulphide.
During hydrothermal reaction, the intermediate complex
slowly decomposed and tiny nuclei of CdS were formed (see
scheme 2A). Initially, tiny nuclei of CdS are produced in the
supersaturated solution and further growth of nanoparticles take
place with time (Scheme 2b). Under prolonged hydrothermal
conditions, the CdS nuclei were grown to form CdS
nanocrystals. The newly formed CdS nanoparticles are
spontaneously aggregated to minimize their surface energy.
These nanoparticles further grow anisotropically along the 2D
direction results formation of thin nanopetals like
morphology (Scheme2b&c).
Fig.5. Photoluminescence spectra of CdS
A PL spectrum (Fig.5) of powdered CdS was taken at an
excitation wavelength of 350 nm. A broad emission peak
centred at 550 nm with slight hump at 580 nmwas observed.
After deconvolution of the original spectra, two separate peaks
at 535 and 568 nm were seen. The PL peak at 535 nm attributed
to bandꢀedge emission whereas, the peak at 568nm is
3
4
Scheme. 2. Growth mechanism for CdS nanostructure
corresponds to surface emissions or possible metal vacancies.
3
.1.6. FORMATION AND GROWTH MECHANISM
5
2
Initially, these nanopetals are transformed into curving
nanopetals due to the surface strain created by vapor
pressure of solvent at hydrothermal condition (scheme 2c).
At prolonged hydrothermal reaction time, further growth is
hindered due to reduction in the precursor concentration.
Hence, with prolong reaction time, these curving nanopetals are
The probable mechanism for the formation of cadmium
sulphide nanostructures by using Lawesson’s reagent (L.R) can
be envisioned as follows.
selfꢀassembled and form a 3D hierarchical nanostructure i.e
.
flower like structure (depicted in scheme 2d).Additionally, the
use of chloroform as a solvent for this reaction is aiding the
formation of CdS nanostructures. Generally, the dielectric
constant of solvents governs the morphology of the product.
The use of ethylenediamine gives rod like morphology which is
well known for one dimensional growth due to its pristine
structure whereas ethylene glycol produce spherical particles.
It is quite well known that the use of different solvents with
Scheme 1. Mechanism of formation of CdS
different
dielectric
constant
produces
different
5
2
Cadmium nitrate (aqueous), reacts with LR compound which morphologies. The BET surface area of CdS nanostructure
on dissolution with chloroform, dissociate to form a monomer was observed to be 54 m /g.
2
4
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ART38ICLE
improves the hydrogen evolution rate. Chemical interactions
between cadmium sulphide and another semiconductor or metal
3
.1.7. PHOTOCATALYTIC H2S SPLITTING
Photocatalytic study was performed using synthesized cadmium will affect the low energy surface states of cadmium sulphide,
sulphidefor Hydrogen generation using H S. Fig. 6 represents leading to an enhanced activity.
2
the graph of H evolution as function of irradiation time. The Hence, under the given experimental conditions, the presence
2
Hydrogen production rate achieved was 14,136 µmol/h/g which of a sacrificial agent, an electron sink in the form of Pt on the
is much higher than earlier reports for the same photocatalyst surface and the size of the photocatalyst particles have
1
7ꢀ26
(
supporting information Table S1).
It also showed good perceptible influence on the photocatalytic hydrogen
stability under the same experimental conditions.
In 0.25 M KOH solution (pH 12.5), the weak diprotic acid H2S alcohol gave highest H gas evolution around 2,065 µmol/h/g.
production. Among the studied sacrificial reagents, benzyl
2
8
2
(
two pKa values are 7.0 and 11.96) dissociates and maintains In presence of Na S and Na SO rate of H production is 1, 060
2 2 3 2
equilibrium with hydrosulphide HSꢁ ions (1). The CdS absorbs µmol/h/g whereas, in presence of methanol lower rate of H2
light and generates electronꢀhole pairs (2). The photoꢀgenerated generation was observed (223 µmol/h/g).
+
valence band hole (h VB) upon band gap excitation of
2
ꢀ
CdSnanopowder oxidizes the HSꢁ ion to disulphide ion (S2 ),
liberating a proton from the HSꢁ ion (3). The conduction band
ꢀ
electron (e CB) from CdS photocatalyst reduces protons to
produce molecular hydrogen (4).
ꢀ
ꢀ
H S+OH
HS +H O
(1)
(2)
(3)
(4)
2
2
+
ꢀ
Semiconductor CdS
Oxidation: 2HS + 2h VB
Reduction: 2H + 2e CB
h VB + e CB
ꢀ
+
2ꢀ
+
S2 +2H
+
ꢀ
H2
Fig.7. Photocatalytic Hydrogen evolution from water Vs irradiation time
We also performed the H generation in absence of Pt as a coꢀ
2
catalyst and found 103 µmol/h/g of H evolution. The TEM
2
images of Ptꢀloaded CdS are also depicted in supporting
information (Fig.S4). In absence of Pt the formed electronꢀhole
pair recombines rather being getting separated which result
lower H evolution.
2
Considering the earlier reports for H S splitting, the flowers of
2
2
Fig.6. Photocatalytic Hydrogen evolution from H S Vs Time
CdS gave enhanced photocatalytic activity due to high aspect
ratio. If we see the FESEM carefully, each petal has average
size is 0.5 (W) X 1.5(L) µm. Each petal has an average
thickness around 40 to 50 nm. The flower is composed of such
individual petals which ultimately have higher aspect ratio. All
flowers are observed to be puffy in nature and greatly expose to
the light. Hence, maximum surface is exposed to the light
which enhances overall photoꢀabsorption which ultimately
increases photoꢀgenerated charge carriers, significantly. The
photoluminescence study clearly indicates broad emission peak
at 568nm due to defects created by metal vacancies. This
defects may be acting as a midꢀtrap vacancies which decreases
electron and hole recombination by trapping the holes.
Additionally, due to thin petals (plate structure), transport of
electron to the surface also get enhanced. Since, it is well
known that free electrons are responsible for water and H2S
splitting; the enhancement in hydrogen evolution is quite
The efficiency of our photocatalyst was confirmed by the
experiment which showed that in absence of photocatalyst as
well as in dark condition, evolution of hydrogen gas was not
observed from 0.25 M KOH solution flushed with H S gas
2
under the visible light irradiation. Also, we carried out the
recycle study of CdS nanostructures and found almost same
hydrogen production even after three cycles. (see supporting
information Table S2)
1
7
3
.1.8. PHOTOCATALYTIC HYDROGEN GENERATION FROM WATER
The photocatalytichydrogen generation was carried out using
prepared CdS nanostructures in presence of three different
sacrificial reagents viz., a) methanol b) 0.1M Na S and 0.04M
2
Na SO and c) 2ml Benzyl alcohol dissolved in 5ml acetic acid.
2
3
For this purpose we used 100 mL DI water and 100 mg Pt
loaded CdS nanostructures.The Pt acts as a coꢀcatalyst and
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justifiable. Additionally, the surface area observed to be fairly for the formation of monomer (B), Fig. S2 TEM images of CdS
1
larger which is also responsible for good activity.
nanostructures and PtꢀCdS, Fig.S3 and S4 H NMR spectra of side
production with earlier
S generation table S2. See
The stability of the photocatalyst is already confirmed by products A and B respectively. Comparison of H
2
performing recycle experiments. The chemistry of photoꢀ reports Table S1 and the recycle study of H
corrosion is well understood in case of CdS for water splitting. DOI: 10.1039/b000000x/
However, in case of H S splitting reaction in presence of
2
2
a
Centre for Materials for Electronic Technology (CꢀMET), Govt of India,
Panchawati, Off Pashan Road, Pune 411008, India. Eꢀmail:
ultimately the formation of Cd ions also negligible. There is a kbbb1@yahoo.com, bbkale@cmet.gov.in; Fax: +91ꢀ20ꢀ25898085; Tel:
sacrificial reagents, the photoꢀcorrosion process is hindered and
+
91ꢀ20ꢀ25898390
continuous supply of H S during reaction which favours the
CdS formation and suppresses the formation of Cadmium ion
2
b
National Chemical Laboratory (NCL), Dr.HomiBhabha Road, Puneꢀ
4
11008, India.
c
or any other cadmium compound. In case of H production
Department of Physics, University of Pune, Puneꢀ411007, India
2
from H S, Cd ions (if formed) may be reacting with the S ions
2
which are already available as per reaction (1) in alkaline References
medium. Even if the Cd ion or CdO formed we can easily
convert it into CdS by treating it with Lawesson’s reagent.
Hence, in technological point of view, catalyst regeneration is
very easy in the present system. In view of the above, there
will not be any leaching and disposal of Cadmium which avoids
the environmental issue. The large scale production of CdS
nanostructures using the Lawesson’s reagent is possible. With
the use of sophisticated equipment’s (Parr reactor) the CdS with
same physicoꢀchemical properties can be reproducible.
1
H. M. Chen, C. K. Chen, R. Liu, L. Zhang, J. Zhang, D. P.
Wilkinson, Chem. Soc. Rev.,2012, 41, 5654ꢀ5671.
X. Chen, C. Li, M. Gratzel, R. Kosteckid, S. S. Mao, Chem. Soc.
Rev., 2012, 41, 7909ꢀ7937.
2
3
4
F. E. Osterloh, Chem. Soc. Rev., 2013, 42, 2294ꢀ2320.
P. Zhang, J. Zhang, J. Gong. Chem. Soc. Rev., DOI:
10.1039/c3cs60438a.
5
6
7
8
J. Ran, J. Zhang, J. Yu, M. Jaroniecc, S. Z. Qiao, Chem. Soc. Rev.,
DOI:10.1039/c3cs60425j.
T. Hisatomi, J. Kubota, K. Domen, Chem. Soc. Rev., 2014, 43, 7520ꢀ
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4
. Conclusions
H. You, S. Yang, B. Dinga, H. Yang, Chem. Soc. Rev., 2013, 42
880ꢀ2904.
H. Kind , H. Yan , B. Messer , M. Law , P. D. Yang , Adv. Mater.
002,14, 158ꢀ160.
,
In summary, we have architectured hierarchical CdS
nanostructures i.e. carnation flower like morphology using
simple hydrothermal method. We have used Lawesson’s
reagent as a sulphur source as well as a capping agent for the
first time. Considering the unique morphology, the possible
formation mechanism has been furnished. The CdS Carnation
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flowers showed highest photocatalytic H evolution i.e. 14,136
2
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µmol/h/g for H S splitting which is much higher than the earlier
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2
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photocatalytic activity is due to puffy flower like morphology
which ultimately enhances photoꢀabsorption and photoꢀ
generated charge carriers. More significantly, the catalyst has
shown very stable activity after recycles. Such kinds of
nanostructures are attractive candidates for solar cell and other
optoelectronic devices. The present investigation will be greatly
helpful for the synthesis of other hierarchically nanostructured
metal chalcogenides from Lawesson’s reagent.
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Schematic representation of H S splitting setup, Scheme S1. Mechanism
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