One-step vulcanization of Cd(OH)Cl nanorods to synthesize CdS/ZnS/PdS nanotubes for highly efficient photocatalytic hydrogen evolution

Article abstract of DOI:10.1039/c9ta03862k

In this work, a novel strategy, one-step vulcanization of Cd(OH)Cl nanorods in the presence of ZnCl₂ and Na₂PdCl₄, is successfully developed to synthesize CdS/ZnS/PdS nanotubes (NTs) for the first time. In this method, the

Full text of DOI:10.1039/c9ta03862k

View Article Online
View Journal
Journal of
M at erials Chemistry A
Accepted Manuscript
This article can be cited before page numbers have been issued, to do this please use: G. Sun, S. Mao, D.
Ma, Y. Zou, Y. Lv, Z. Li, C. He, Y. Cheng and J. Shi, J. Mater. Chem. A, 2019, DOI: 10.1039/C9TA03862K.
Volume
4
Number
1
7
January 2016 Pages 1–330
This is an Accepted Manuscript, which has been through the
Royal Society of Chemistry peer review process and has been
accepted for publication.
Journal of
Materials Chemistry A
Accepted Manuscripts are published online shortly after
Materials for energy and sustainability
www.rsc.org/MaterialsA
acceptance, before technical editing, formatting and proof reading.
Using this free service, authors can make their results available
to the community, in citable form, before we publish the edited
article. We will replace this Accepted Manuscript with the edited
and formatted Advance Article as soon as it is available.
You can find more information about Accepted Manuscripts in the
author guidelines.
Please note that technical editing may introduce minor changes
to the text and/or graphics, which may alter content. The journal’s
standard Terms & Conditions and the ethical guidelines, outlined
in our author and reviewer resource centre, still apply. In no
event shall the Royal Society of Chemistry be held responsible
for any errors or omissions in this Accepted Manuscript or any
consequences arising from the use of any information it contains.
ISSN 2050-7488
PAPER
Kun Chang, Zhaorong Chang et al.
Bubble-template-assisted synthesis of hollow fullerene-like
MoS nanocages as a lithium ion battery anode material
2
rsc.li/materials-a

Page 1 of 26
Journal of Materials Chemistry A
View Article Online
DOI: 10.1039/C9TA03862K
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
One-step vulcanization of Cd(OH)Cl nanorods to synthesize CdS/ZnS/PdS
nanotubes for highly efficient photocatalytic hydrogen evolution
a
a
a
a
a
a
b
Guotai Sun, Siman Mao, Dandan Ma, Yajun Zou, Yixuan Lv, Zhihui Li, Chi He, Yonghong
a
a,
Cheng, Jian-Wen Shi, *
a
State Key Laboratory of Electrical insulation and Power Equipment, Center of Nanomaterials for
Renewable Energy, School of Electrical Engineering, Xi'an Jiaotong University, Xi'an 710049,
China.
b
Department of Environmental Science and Engineering, School of Energy and Power Engineering,
1
1
1
1
1
1
1
1
1
1
2
2
2
Xi’an Jiaotong University, Xi’an 710049, China
Corresponding author:
Jian-Wen Shi, E-mail: jianwen.shi@mail.xjtu.edu.cn
1

Journal of Materials Chemistry A
Page 2 of 26
View Article Online
DOI: 10.1039/C9TA03862K
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
Abstract
In this work, a novel strategy, one-step vulcanization of Cd(OH)Cl nanorods in the presence of
ZnCl and Na PdCl is successfully developed to synthesize CdS/ZnS/PdS nanotubes (NTs) for the
2
2
4
first time. With this method, the three components (CdS, ZnS and PdS) are fully combined together
at nano-scale in the CdS/ZnS/PdS NTs, creating a large number of intimate contact interfaces. As a
result, the optimized CdS/ZnS/PdS NTs exhibit a significantly enhanced photocatalytic H evolution
2
rate of 1021.1 μmol/h (10 mg of catalyst), which is 11.4 and 16.3 times higher than that of the
pristine CdS NTs and ZnS nanoparticles (NPs), respectively, and is the maximum reported in CdS-
based photocatalysts under similar experimental conditions. Moreover, the apparent quantum
efficiency of the optimal sample can reach 26.1 % at 365 nm wavelength. The improved
photocatalytic performance can be attributed to the synergistic effects of the hollow tubular structure,
the CdS/ZnS heterostructure and the PdS co-catalyst. Due to the hollow tubular structure, both the
inner and outer surfaces of CdS/ZnS/PdS NTs can act as the reaction sites to rapidly consume
electrons and holes, effectively suppressing their recombination. Both the CdS/ZnS heterostructure
and the PdS co-catalyst can efficiently promote the separation and transfer of charge carriers. This
work may provide a new method for the design and construction of new photocatalysts with highly
efficient H production.
2
Keywords: Photocatalysis; Hydrogen evolution; Water splitting; Heterostructure; CdS nanotube
2

Page 3 of 26
Journal of Materials Chemistry A
View Article Online
DOI: 10.1039/C9TA03862K
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
6
6
6
6
6
6
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
1. Introduction
Hydrogen is a promising energy source because of its clean product and high combustion heat.
Photocatalytic H evolution from water splitting to solve energy and environmental issues has
2
1
attracted extensive attention since the pioneering report by Fujishima and Honda in 1972. A large
number of semiconductors, such as TiO2, 2-5 C N ,
6-10
and transition metal sulfides, 11-18 have been
3
4
widely developed as photocatalysts for hydrogen evolution. Among the numerous photocatalysts,
CdS has drawn increasing attention due to its narrow bandgap (2.4 eV) and the suitable band
1
9
structure for photocatalytic H evolution reaction. However, the practical application of CdS is
2
still severely restricted by the rapid recombination of photo-generated charge carriers. 20-22
Several strategies have been developed to promote the separation and transfer of photo-
generated charge carriers, such as morphology control, 15, 23-27 heterostructure construction, 28-33 and
co-catalyst deposition. 34-42 It has been demonstrated that one-dimensional (1D) structure can realize
a fast and long-distance electron transport, 43 resulting in enhanced separation efficiency of
photoexcited electrons and holes. Therefore, 1D CdS nanomaterials have been widely developed,
such as CdS nanorods, 32 nanowires, 44 and nanobelts. 45 Meanwhile, the hollow-structured
photocatalysts are attracting more and more attention due to several unique advantages including
low density, high light-harvesting efficiency, and more reaction sites. 46-48 As an important member,
hollow porous CdS photocatalyst has been widely investigated. 15 However, the hollow CdS
nanotubes (NTs) have been reported only once, 49 where the hollow CdS NTs were successfully
prepared, but no studies were made on their properties. Heterostructure construction is another
effective means to promote the separation and migration of charge carriers. As a promising
heterostructure, CdS/ZnS has attracted a lot of interest in recent years. 32, 50-52 It has been reported
3

Journal of Materials Chemistry A
Page 4 of 26
View Article Online
DOI: 10.1039/C9TA03862K
6
6
6
7
7
7
7
7
7
7
7
7
7
8
8
8
8
8
8
8
8
8
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
that CdS/ZnS exhibited relatively high activity in photocatalytic hydrogen evolution due to the
effective suppression of electron-hole recombination. 32 However, CdS/ZnS is usually synthesized
through two-step method, for example, ZnS nanocrystals were grown on CdS nanorods, 32 or CdS
nanoparticles were deposited on ZnS nanoparticles, 52 thus the resultant heterostructures usually
present a clear interface between the two semiconductors, resulting in their limited contact, which
is unfavorable for the transfer of photogenerated electrons and holes. As a result, the photocatalytic
H evolution rate of CdS/ZnS is still far below the actual application requirements. Additionally,
2
co-catalyst deposition has been widely demonstrated to promote the separation and migration of
charge carriers, and Pt, 12, 40, 53 Au, 48, 50, 54 and PdS, 15, 40 have been widely utilized as co-catalysts
to boosting photocatalytic H evolution. It should be noted that co-catalyst is usually deposited on
2
the surface of the main-catalyst by photo-deposition, thus only limited interface contacts between
co-catalyst and main-catalyst can be formed, which is unfavorable for the effective transfer of
charge carriers.
Based on the above considerations, in this work, we skillfully combined the three strategies
together to synthesize 1D CdS/ZnS/PdS NTs, where CdS and ZnS constructed heterostructure and
PdS played as co-catalyst. It is worth mentioning that a novel strategy, one-step vulcanization of
Cd(OH)Cl nanorods in the presence of ZnCl and Na PdCl , was successfully developed for the first
2
2
4
time to synthesize CdS/ZnS/PdS NTs. With this method, the three components (CdS, ZnS and PdS)
were fully combined together at nano-scale, which created a large number of intimate contact
interfaces. Although the obtained CdS/ZnS/PdS NTs exhibited a low crystallinity as other hollow
porous CdS photocatalyst reported, 15 the hollow tubular structure and the full mixing of three
components at nanoscale made up for the defect of low crystallinity. As a result, the optimized
4

Page 5 of 26
Journal of Materials Chemistry A
View Article Online
DOI: 10.1039/C9TA03862K
8
9
9
9
9
9
9
9
9
9
9
9
0
1
2
3
4
5
6
7
8
9
CdS/ZnS/PdS NTs exhibited a notably enhanced photocatalytic H evolution rate of 1021.1 μmol/h
2
(corresponding to 102.11 mmol/g/h, 10 mg of catalyst), which was the maximum reported in CdS-
based photocatalysts under the similar experimental conditions. The reasons for significantly
improved photocatalytic performance were discussed in details.
2. Experimental section
2.1 Synthesis of Cd(OH)Cl nanorods
As the precursor, Cd(OH)Cl nanorods were firstly prepared according to a previous report, 49
as follows: Firstly, the NaOH solution (1 M, 30 mL) was poured into the CdCl solution (1 M, 30
2
mL) containing 3 wt% polyvinyl pyrrolidone (PVP) under stirring to produce precipitate. Then, the
o
obtained precipitate was successively heated at 90 C for 12 h in an oil bath, filtered, washed with
o
distilled water and ethanol, and finally dried at 60 C in a vacuum oven, resulting in Cd(OH)Cl
1
00
01
02
03
04
05
06
07
08
09
10
nanorods.
1
1
1
1
1
1
1
1
1
1
2.2. Synthesis of CdS NTs
Typically, the obtained Cd(OH)Cl nanorods (570.6 mg) were firstly dispersed into 25 mL of
aqueous solution under magnetic stirring, and then the thioacetamide (289.1 mg) was added into the
suspension. After half an hour, a yellow precipitate was obtained, which then was centrifuged,
o
washed with distilled water and ethanol for several times, and finally dried at 40 C in a vacuum
oven, resulting in CdS NTs.
2.3. Synthesis of CdS/ZnS, CdS/PdS, and CdS/ZnS/PdS NTs
The CdS/ZnS NTs were synthesized by the same procedure as the synthesis of CdS NTs except
that a certain amount of ZnCl was added into 25 mL aqueous solution. The weight ratio of ZnS to
2
CdS was adjusted by the added amount of ZnCl under the condition that the amount of Cd(OH)Cl
2
5

Journal of Materials Chemistry A
Page 6 of 26
View Article Online
DOI: 10.1039/C9TA03862K
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
nanorods kept constant (570.6 mg). Thus, three CdS/ZnS NTs with different weight ratios of ZnS
to CdS (1 %, 3 % and 5 %) were obtained. For convenience, they were marked as CZ S, CZ S, and
1
3
CZ S, respectively. The synthesis of CdS/PdS NTs was exactly the same as the synthesis of
5
CdS/ZnS NTs except that ZnCl was replaced by Na PdCl (10.62 mg), and the resultant sample
2
2
4
was labelled as CP S where the weight ratio of PdS to CdS NTs was calculated to be 1 %. The
1
CdS/ZnS/PdS NTs were synthesized by the same procedure as the synthesis of CdS NTs except that
both 20.98 mg of ZnCl and 10.62 mg of Na PdCl were added into 25 mL aqueous solution. The
2
2
4
resultant CdS/ZnS/PdS NTs were marked as CZ P S where the weight ratio of ZnS to CdS was 3 %
3
1
and the weight ratio of PdS to CdS was 1%. The preparation process of the CZ P S sample is shown
3
1
in Scheme 1 (the detailed chemical reaction processes were shown in Supporting Information).
In addition, in order to prove the advantages of the one-step vulcanization method, a
counterpart, CdS NTs loaded 1 wt% PdS was prepared by photo-deposition method, as follows: 10
mg of CdS NTs was dispersed in 25 mL of aqueous solution contained 0.35 M Na S and 0.25 M
2
Na SO to form a uniform suspension. Then, 1 mL of Na PdCl aqueous solution (0.1 mg/mL) was
2
3
2
4
added to the suspension and then irradiated with Xe lamp under stirring for 0.5 h. The resultant
product was collected and washed with distilled water for several times, and then was dried at 40 °C,
resulting in CdS/1 wt % PdS.
6

Page 7 of 26
Journal of Materials Chemistry A
View Article Online
DOI: 10.1039/C9TA03862K
1
29
30
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
Scheme 1. Schematic illustration of the preparation of the CZ P S sample.
3
1
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
2.4. Synthesis of ZnS NPs
For comparison, the pristine ZnS NPs were synthesized by the same procedure, as follows:
349.62 mg of ZnCl was firstly dissolved into 25 mL of aqueous solution under magnetic stirring,
2
and then 289.1 mg of thioacetamide was added into the above solution. After half an hour, a white
precipitate was obtained, which then was centrifuged, washed with distilled water and ethanol for
o
several times, and finally dried at 40 C in a vacuum oven, resulting in ZnS NPs.
2.5. Photocatalytic hydrogen evolution
The photocatalytic H evolution experiments were performed in a top-irradiation quartz cell
2
connected to a photocatalytic H evolution system (CEL-SPH2N, Beijing). 10 mg of the as-prepared
2
photocatalyst was suspended in 25 mL of distilled water including 0.25 M of sodium sulfite and
0.35 M of sodium sulfide as sacrificial agents. The total illumination time of each measurement was
3 h, which was provided by a 225 W Xe lamp (320-780 nm). The TCD gas phase chromatograph
(GC-9720) was employed to determine the amount of H evolution. The carrier gas was nitrogen
2
o
(N ). The reaction temperature was controlled at around 6 C by a water-cooling circulation system.
2
2.6. Characterization
X-ray powder diffraction (XRD) patterns of the samples were obtained on a Bruker D2 Phaser
7

Journal of Materials Chemistry A
Page 8 of 26
View Article Online
DOI: 10.1039/C9TA03862K
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
diffractometer using Cu K radiation (λ = 1.5418 Ǻ) at a voltage of 40 kV and a current of 30 mA.
α
Transmission electron microscopy (TEM) images and high-resolution TEM (HRTEM) images were
conducted by using a JEOL JEM2100 TEM operated at 200 kV. Scanning electron microscopy
(SEM) images were carried out on a FEI Quanta 250 SEM. The specific surface area and pore
distribution were recorded on a Quantachrome Autosorb IQ analyzer. UV-visible absorption spectra
were measured by a V-670 spectrophotometer with an integrating sphere. Photoluminescence (PL)
spectra were obtained on an Edinburgh Instruments FLS980 spectrometer using a 325 nm excitation
wavelength. X-ray photoelectron spectroscopy (XPS) measurement was performed on a Thermo
Fisher Scientific ESCALAB spectrometer with aluminum K radiation.
α
2.7. Photoelectrochemical measurement
Photocurrent experiments and electrochemical impedance spectra (EIS) were measured by
using a CHI 660E in a standard three-electrode system with the photocatalyst-coated FTO as the
working electrode, Ag/AgCl as a reference electrode and Pt plate as the counter electrode. 1 M of
Na SO aqueous solution was applied as the electrolyte. A 225W Xe lamp was used as simulated
2
4
solar light source and light on and off was transformed in every 20 s.
3. Results and discussion
The XRD was carried out to reveal the crystal phase information of the as-prepared samples.
The Cd(OH)Cl nanorods exhibited the typical diffraction peaks of hexagonal Cd(OH)Cl (JCPDS
74-1047) (Fig. S1a). The diffraction peaks of CdS NTs and ZnS NPs matched well with the
hexagonal CdS phase (JCPDS 41-1049) and cubic ZnS phase (JCPDS 79-0043), respectively (Fig.
1). The other nanotube samples, such as CZ S, CP S and CZ P1S, shared the similar diffraction
3
1
3
peaks as CdS NTs except that their XRD peaks were wider than that of CdS NTs (Fig. 1), indicating
8

Page 9 of 26
Journal of Materials Chemistry A
View Article Online
DOI: 10.1039/C9TA03862K
1
69
70
71
72
that the introduction of Zn and/or Pd can restrain the crystallinity of hexagonal CdS. 49 For the
diffraction peaks of CdS/ZnS composites, there were no obvious peaks of ZnS due to the small
added amount of ZnS. 55 Similarly, no obvious diffraction peaks of PdS were observed for the
CZ P S sample, probably because the amount of PdS is too small.
1
1
1
3
1
1
1
73
74
Fig. 1. XRD patterns of CdS, CdS/ZnS, CdS/PdS, CdS/ZnS/PdS NTs and ZnS NPs.
1
1
1
1
1
1
1
1
1
1
1
1
75
76
77
78
79
80
81
82
83
84
85
86
The morphology and microstructure of the as-synthesized samples were characterized by TEM
and SEM measurements. As shown in Fig. S1b, the as-prepared precursor, Cd(OH)Cl presented the
morphology of nanorod with a diameter of about 120 nm and a length of about 300-600 nm. After
vulcanization treatment by using thioacetamide, the interior of the nanorod was hollowed out to
form the structure of the nanotube, and as a result, the pristine CdS exhibited the tubular structure
with an outer diameter of about 150 nm and a wall thickness of about 25 nm (Fig. 2a). Compared
with the smooth surface of Cd(OH)Cl nanorods, the surface of CdS NT was rough a little, and some
fine nanoparticles could be observed, which can be attributed to the fact that the CdS NT was consist
of numerous nanoparticles with a diameter of about 6 nm. Further amplification, we found that the
lattice fringe with a d spacing of 0.336 nm from the HRTEM image of pristine CdS NTs (Fig. 2b),
which matches well with the (002) plane of the hexagonal CdS structure, confirming that Cd(OH)Cl
has been transformed to CdS due to the vulcanization treatment, which is consistent with the result
9

Journal of Materials Chemistry A
Page 10 of 26
View Article Online
DOI: 10.1039/C9TA03862K
1
1
1
1
1
1
1
1
1
1
87
88
89
90
91
92
93
94
95
96
of XRD. When ZnCl or/and Na PdCl was added to trigger the sulfidizing process of Cd(OH)Cl,
2 2 4
the resultant CdS/ZnS (Fig. S2a), CdS/PdS (Fig. S2c), and CdS/ZnS/PdS (Fig. 2c) still exhibited
tubular structure with roughly equal diameter and rougher surface. By comparison, the pristine ZnS
displayed the uniform granular morphology with a diameter of about 5-7 nm (Fig. 2g), and the
interplanar spacing of 0.27 nm belonging to (200) plane of cubic ZnS was observed (Fig. 2h).
Further amplifying the tubular wall of CZ P S, three kinds of lattice fringes, 0.336, 0.27 and 0.23
3
1
nm, were detected, which correspond to (002), (200) and (202) planes of CdS, ZnS and PdS,
respectively. 15, 40, 55 The three sulfides connected intimately with each other to form close contact
interfaces of CdS-ZnS (Fig. 2d), CdS-PdS (Fig. 2e) and CdS-ZnS-PdS (Fig. 2f), resulting in a
ternary heterostructure.
1
0

Page 11 of 26
Journal of Materials Chemistry A
View Article Online
DOI: 10.1039/C9TA03862K
1
1
97
98
99
00
01
02
Fig. 2. TEM images of the CdS NTs (a, b), CZ P S (c-f) and ZnS (g, h).
3
1
1
2
2
2
Fig. S3 shows the SEM images of the as-prepared samples, which is the same as that revealed
by TEM images. By making comparisons of these SEM images, three points can be concluded: 1)
nanotubes were formed, whether for the pristine CdS or the binary CdS/ZnS, or the ternary
CdS/ZnS/PdS; 2) the surface of nanotubes became rougher and rougher with the increase of ZnS
1
1

Journal of Materials Chemistry A
Page 12 of 26
View Article Online
DOI: 10.1039/C9TA03862K
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
03
04
05
06
07
08
09
10
11
12
13
14
15
16
17
18
19
20
21
22
23
content; 3) Some flocculent substances attached on the outer surface of nanotubes were formed in
the presence of Na PdCl , which can be ascribed to the formed PdS NPs. These flocculent
2
4
substances should have contribution to the improvement in the specific surface area (SBET) of sample.
As confirmed by the results of N adsorption and desorption (Fig. S4), the S of the CZ P S
2
BET
3 1
2
2
sample (87.82 m /g) was apparently larger than that of CdS NTs (64.71 m /g).
As a typical sample, the CZ P S sample was further characterized by HAADF STEM imaging
3
1
(Fig. 3a) and EDS elemental mappings (Fig. 3b-e). These dots represented the distribution of Cd
and S elements were uniform and dense (Fig. 3b, c) and outlined a hollow tubular structure.
Compared with Cd and S, the dots represented Zn and Pd elements were uniform and scattered (Fig.
3d, e), which can be attributed their low dosages. It should be noted that Zn and Pd were distributed
throughout the tube wall. There was no obvious interface between the distribution of Zn (or/and Pd)
and Cd (or/and S), indicating that ZnS and PdS were fully combined with CdS at nano-scale, which
is totally different with the commonly used vulcanization method where only vulcanizing agent
(thioacetamide, here) was added, 28, 29 without metal precursors of target sulfides (ZnCl and
2
Na PdCl in current work). Thus, a clear interface usually occurs between the vulcanized product
2
4
and the precursor, 28 resulting in limited contact interface between them (semiconductors), which is
unfavorable for the transfer of photogenerated electrons and holes. In order to clarify the percentages
of S, Cd, Zn and Pd in the as-prepared samples, EDS was carried out (Fig. S5), and the obtained
data were summarized in Table S1. Clearly, the percentages of Zn and Pd in the as-prepared samples
were close to their dosages, suggesting that all additions of Zn and Pd have been converted to their
corresponding sulfides and combined with CdS together.
1
2

Page 13 of 26
Journal of Materials Chemistry A
View Article Online
DOI: 10.1039/C9TA03862K
2
2
24
25
26
27
28
29
30
31
32
33
34
35
36
Fig. 3. HAADF STEMimage (a) and EDS mappings (b-e) of the CZ P S sample.
3
1
2
2
2
2
2
2
2
2
2
2
2
The XPS of the CZ P S sample was conducted to investigate the chemical composition and
3 1
elemental valence state. The XPS survey scan (Fig. 4a) confirmed the existence of Cd, S, Zn, Pd,
O and C elements. The peak of C at 284.6 eV mainly attributed to the double side tape for the
5
6
preparation of test sample, including the CO adsorbed on the surface of sample. The peak of O
2
5
7
1s can be ascribed to the CO and H O absorbed on the surface of the sample. The spectrum of S
2
2
2p was divided into two peaks with binding energies at 161.0 and 162.2 eV (Fig. 4b), corresponding
2
-
58
to S 2p3/2 and S 2p , respectively, suggesting the existence of S in the sample. Similarly, the
1/2
spectrum of Cd 3d exhibited two peaks at 404.6 and 411.3 eV (Fig. 4c), corresponding to Cd 3d5/2
5
9
and Cd 3d , respectively. Meanwhile, the two peaks centered at 1020.9 and 1044.1 eV in the
3
/2
spectrum of Zn 2p (Fig. 4d) were assigned to Zn 2p and Zn 2p , respectively, indicating the
3
/2
1/2
2
+ 60
oxidation state of Zn . Besides, the peaks at 336.3 and 341.6 eV attributed to Pd 3d and Pd 3d3/2
5
/2
1
3

Journal of Materials Chemistry A
Page 14 of 26
View Article Online
DOI: 10.1039/C9TA03862K
2
+ 40
2
2
2
37
38
39
were observed in Fig. 4e, suggesting the presence of Pd . Moreover, the percentages of Zn and
Pd in the CZ P S sample were also measured by XPS. As shown in Table S2, their percentages
3
1
were close to their dosages, in agreement with the result of EDS.
2
2
40
41
Fig. 4. XPS survey spectrum (a) and high-resolution XPS spectra of S 2p (b), Cd 3d (c), Zn 2p (d)
2
2
2
2
2
2
2
2
2
2
42
43
44
45
46
47
48
49
50
51
and Pd 3d (e) of the CZ P S sample.
3
1
The UV-vis absorption spectra of the as-prepared samples are shown in Fig. 5a, and the
corresponding Tauc plots used to estimate the band gaps (Table S3) of the samples by applying the
1
/2
equation α(hν) = A(hν - E ) ; (where α is the absorption coefficient, hν is the photon energy, A is a
g
constant, and E is the band gap energy) are displayed in Fig. S6. The CdS NTs presented strong
g
absorption from the UV to visible light region (200-600 nm) due to its narrow band gap (2.4 eV).
1
9, 61
By comparison, the pristine ZnS NPs only exhibited relatively strong absorption in the UV
region (200-350 nm) because of its wide band gap (3.6 eV). 62, 63 Owing to the low percentage of
ZnS, CdS/ZnS NTs presented the UV-visible absorption spectrum similar to CdS NTs with a slight
blue shift. Meanwhile, the absorption edge of CdS/PdS NTs showed an obvious red shift to longer
1
4

Page 15 of 26
Journal of Materials Chemistry A
View Article Online
DOI: 10.1039/C9TA03862K
2
2
2
52
wavelength in comparison with pristine CdS NTs owing to the very narrow band gap of PdS (1.6
53
54
eV). 64 As for the ternary CdS/ZnS/PdS, CZ P S exhibited the UV-visible absorption similar to
3
1
CP S with a slight blue shift.
1
2
2
55
56
Fig. 5. The UV-vis absorption spectra (a) and the average photocatalytic hydrogen evolution (10
mg of catalyst) (b) of the as-prepared samples, the UV-vis absorption spectrum and AQE data of
the CZ P S sample (c), the cycling tests (after every cycle, the sample was placed for a week for the
2
2
2
2
2
2
2
2
57
58
59
60
61
62
63
64
3
1
next use) for photocatalytic hydrogen evolution over the CZ P S sample (d).
3
1
The photocatalytic hydrogen evolution rates over these samples under simulated solar light
irradiation without adding any other co-catalysts are displayed in Fig. 5b, and the corresponding
time courses of H evolution are shown in Fig. S7. The pristine CdS NTs presented a H evolution
2
2
rate (89.2 μmol/h), which is relatively higher than that of the CdS with other solid structures, such
as nanoparticles, nanorods, nanospheres, etc., 23, 24, 40, 65 suggesting that the hollow tubular structure
1
5

Journal of Materials Chemistry A
Page 16 of 26
View Article Online
DOI: 10.1039/C9TA03862K
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
is very helpful to improve the photocatalytic hydrogen evolution. It seems very understandable that
the inner surface of nanotubes also acts as the reaction sites to rapidly consume electrons for
hydrogen evolution, which effectively suppresses the recombination of photogenerated electrons
and holes. By comparison, the pristine ZnS NPs showed a lower H evolution rate (62.6 μmol/h)
2
than that of the pristine CdS NTs owing to its wide band gap. For the CdS/ZnS NTs, the H evolution
2
rate increased firstly from 178.4 μmol/h of CZ S to 673.5 μmol/h of CZ S, and then decreased to
1
3
156.2 μmol/h of CZ S, suggesting the percentage of ZnS has an important effect on the H evolution
5
2
rate of CdS/ZnS, and 3 wt% of ZnS is the optimal concentration for the highest H evolution rate.
2
The reason can be attributed to the fact that the moderate addition of ZnS can construct effective
heterojunction with CdS to promote the separation and transfer of charge carries, while superfluous
ZnS can reduce the number of photogenerated charge carries due to its wider band gap than CdS.
Similarly, the introduction of PdS also promoted the H evolution rate of CdS NTs, which increased
2
to 584.8 μmol/h of CP S sample from 89.2 μmol/h of pristine CdS NTs (a 6.6-fold increase). It has
1
been widely confirmed that PdS is an excellent hole-captured co-catalyst. 15, 40, 66 Therefore, the
enhanced H evolution rate of CP S sample can be ascribed to the efficient capture of
2
1
photogenerated holes in the valence band of CdS resulted from the PdS co-catalyst, which inhibits
the recombination of photogenerated electrons and holes and promote their separation and transfer.
Meanwhile, the photocatalytic H evolution rate of CdS loaded 1 wt% PdS by photo-deposition
2
exhibited a lower H evolution rate (223.6 μmol/h) than that of CP S sample (584.8 μmol/h),
2
1
suggesting the one-step vulcanization method is superior to the photo-deposition method. Notably,
due to the synergistic effect caused by ZnS and PdS, the CZ P S sample reached up to the maximum
3
1
value (1021.1 μmol/h), which is 11.4 and 16.3 times higher than that of the pristine CdS NTs and
1
6

Page 17 of 26
Journal of Materials Chemistry A
View Article Online
DOI: 10.1039/C9TA03862K
2
2
2
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
87
ZnS NPs, respectively. We consulted carefully the photocatalytic H evolution rates over different
2
88
89
90
91
92
93
94
95
96
97
98
99
00
01
02
03
04
05
06
07
08
CdS-based photocatalysts reported in literatures (Table S4), and found that the 1021.1 μmol/h is
the current maximum value.
The apparent quantum efficiency (AQE) over the CZ P S sample corresponding to different
3
1
wavelengths (365, 380, 420, and 500 nm) was surveyed. As displayed in Fig. 5c, the AQE decreased
gradually with the increasing irradiation wavelength, which is in accordance with the trend of UV-
vis absorption spectra (the specific values of AQE at different wavelengths are listed in Table S5).
The AQE attained the maximum value of 26.1 % under the irradiation of the 365 nm light, which
can stimulate both CdS and ZnS to generate charge carriers. The cycling tests for photocatalytic
hydrogen evolution were carried out to investigate the stability of the CZ P S sample. Each cycle
3
1
was conducted for 3 h. After one cycle, the tested sample was remained in the solution for a week
for the next use. As shown in Fig. 5d, the hydrogen evolution rate presented almost no decrease
after six cycles (18 h), suggesting that the CZ P S sample possesses an excellent photocatalytic
3
1
stability. Besides, the XRD pattern of the CZ P S sample after six cycles maintained the same as
3
1
the fresh sample (Fig. S8), further demonstrating its excellent photocatalytic stability.
The photoluminescence spectroscopies (PL) were conducted at the excitation wavelength of
325 nm to confirm the charge separation ability of the as-synthesized samples. As shown in Fig. 6a,
the emission peaks centered at about 470 nm, corresponding to the fast recombination of photo-
generated electrons and holes. ZnS presented the highest PL intensity (the inset in Fig. 6a), in
accordance with its lowest H evolution rate. The CdS/ZnS NTs exhibited lower PL intensity than
2
that of the pristine ZnS NPs, and the PL intensity of CZ S sample was lower than that of the pristine
3
CdS NTs, indicating that the heterostructure constituted of CdS and ZnS can effectively promote
1
7

Journal of Materials Chemistry A
Page 18 of 26
View Article Online
DOI: 10.1039/C9TA03862K
3
3
3
3
09
10
11
12
the mobility of charge carriers. Due to the synergic effect of ZnS and PdS, the CZ P S sample
3 1
showed the lowest PL intensity, which matches well with its highest H evolution rate. The result
2
demonstrates that the ternary CZ P S sample with a hollow tubular structure possesses superior
3
1
ability of charge separation and migration.
3
3
13
14
Fig. 6. PL spectra (a), transient photocurrent responses (the applied voltage and the light intensity
2
3
3
3
3
3
3
3
3
3
3
3
3
3
3
15
16
17
18
19
20
21
22
23
24
25
26
27
28
are 0 V and 112 mW/cm , respectively) (b) and electrochemical impedance spectroscopies (c) of
the as-prepared samples.
The transient photocurrent responses (TPR) of as-prepared samples are displayed in Fig. 6b.
The pristine CdS NTs presented a relatively low photocurrent intensity owing to the fast
recombination of electrons and holes. For the CdS/ZnS composites, the photocurrent intensity
became higher than the value of the pristine CdS NTs, demonstrating the heterostructure between
CdS and ZnS can efficiently facilitate the separation and migration of photo-generated charge
carriers. Moreover, it can be obviously observed that the CZ P S sample exhibited the highest
3
1
photocurrent intensity, corresponding to the largest efficiency of charge separation and migration,
which matches well with the results of PL spectra (Fig. 7a). The electrochemical impedance
spectroscopies (EIS) of all the samples were measured to investigate the ability of charge migration.
As shown in Fig. 6c, the CZ P S sample exhibited the smallest semicircle among all the samples,
3
1
suggesting that interfacial electron transfer resistance of the CZ P S sample was significantly
3
1
reduced. The results of PL, TPR and EIS confirmed that the CZ P S sample possesses the optimal
3
1
1
8

Page 19 of 26
Journal of Materials Chemistry A
View Article Online
DOI: 10.1039/C9TA03862K
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
29
charge separation ability, the highest efficiency of charge separation and migration, and the lowest
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
resistance of charge transfer among all the samples, respectively, resulting in its highest
photocatalytic H evolution rate. The root cause can ultimately be attributed to the synergistic effect
2
of the CdS/ZnS heterojunction and the PdS co-catalyst.
To further investigate the charge transfer pathway, time courses of the hydroxyl radicals (·OH)
concentration over the ZnS, CZ S and CZ P S samples were measured. The terephthalic acid (TA)
3
3 1
was used as a tracer due to the facts that the reaction product (2-hydroxyterephthalic acid, TAOH)
of ·OH and TA can produce fluorescence and the fluorescence intensity is positively correlated with
the concentration of ·OH. As shown in Fig. S9a, as time went on, all the three samples exhibited
the increasing fluorescence intensity with minor differences, suggesting that the ·OH was
continually produced under irradiation. Additionally, the increase rate of fluorescence intensity of
the CZ S and CZ P S samples was slightly higher than that of ZnS sample, which can be attributed
3
3 1
to the inhibition of electron-hole recombination in ZnS resulted from the fact that the
photogenerated electrons in ZnS can be effectively transferred to CdS by means of the CdS/ZnS
heterojunction. According to the previous reports, the valence band (VB) position of CdS (+1.88
−
eV) is more negative than E(•OH/H O) (+2.27 V vs NHE) and E(•OH/OH ) (+2.38 V vs NHE)
2
−
while the VB position of ZnS (+2.56 eV) is more positive than E(•OH/H O) and E(•OH/OH ) (Fig.
2
S9b). 28 As a result, only the holes in the VB of ZnS can react with H O or OH to produce ·OH.
−
2
Therefore, the fluorescence result demonstrates that the photogenerated holes are retained in the VB
of ZnS, not transferred to the VB of CdS following the I-type charge carrier-transfer mode, and PdS
does not play a role in increasing the number of holes photogenerated in the VB of ZnS.
1
9

Journal of Materials Chemistry A
Page 20 of 26
View Article Online
DOI: 10.1039/C9TA03862K
3
3
50
51
Scheme 2. Proposed charge transfer mechanism of the CZ P S heterostructure.
3
1
3
3
3
3
3
3
3
3
3
3
3
3
3
52
53
54
55
56
57
58
59
60
61
62
63
64
A schematic of charge transfer was proposed to reveal the mechanism for the improved
photocatalytic performance of the CZ P S sample. As demonstrated by TEM, the CZ P S
3
1
3 1
heterostructure contained three interfaces, CdS/PdS interface, CdS/ZnS interface and PdS/CdS/ZnS
interface, which can form three pathways for the transfer of charge carriers. It has been reported that
the VB position of PdS is estimated to be +1.34 V versus NHE. 15, 40, 66 As displayed in Scheme 2,
at the CdS/PdS interface, as the VB position of PdS is less positive than that of CdS (+1.50 V), PdS
can act as the hole-captured co-catalyst to collect the holes from the VB of CdS, 15, 40, 66 while the
+
excited electrons from the conduction band (CB) of CdS reduce H to produce H (pathway Ⅰ). For
2
the interface between CdS and ZnS, the photogenerated holes of ZnS remained in the VB of itself
and the holes in the VB of CdS can transfer to the energy band of ZnS due to the intrinsic defects
3
2, 55, 67, 68
in ZnS including sulfur vacancies (V ) and interstitial sulfur (I ),
and then both of two
s
S
kinds of holes reacted with sacrificial agents. Meanwhile, the excited electrons in the CB of ZnS
can migrate to the CB of CdS and then generate H (pathway Ⅱ). At the CdS/ZnS/PdS ternary
2
2
0

Page 21 of 26
Journal of Materials Chemistry A
View Article Online
DOI: 10.1039/C9TA03862K
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
65
interface, due to PdS possessed a strong ability of trapping holes, the photogenerated holes of CdS
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
transferred to PdS and then reacted with sacrificial agents. Meanwhile, the holes of ZnS remained
in the VB of itself according to the above-mentioned fluorescence result (Fig. S9a) and then reacted
+
with sacrificial agents. Similarly, the excited electrons of ZnS transferred to CdS to reduce H to H
2
(pathway Ⅲ). Based on the above experimental results, the rational design of PdS/CdS/ZnS
heterostructure can effectively suppress the recombination of charge carriers and significantly
enhance the photocatalytic performance for H evolution.
2
4. Conclusions
In summary, a novel strategy, one-step vulcanization of Cd(OH)Cl nanorods in the presence of
ZnCl and Na PdCl has been successfully developed to synthesize CdS/ZnS/PdS nanotubes. The
2
2
4
as-prepared CZ P S nanotubes exhibited superior photocatalytic H evolution rate of 1021.1 μmol/h,
3
1
2
which was 11.4 and 16.3 times higher than that of the pristine CdS NTs and ZnS NPs, respectively,
and the AQE was as high as 26.1 % under the irradiation of the 365 nm light. In addition, the CZ P S
3
1
sample presented excellent stability for photocatalytic H evolution without apparent decay within
2
six cycles in 18 h. The synergistic effects of hollow structure and ternary heterostructure effectively
promoted the separation and migration of charge carriers, and improved its photocatalytic H2
evolution ability. This work may provide a strategy for the design and preparation of other
photocatalysts for highly efficient H evolution.
2
Acknowledgement
This work was financially supported by the Natural Science Foundation of Shaanxi Province,
China (2019JM-154), the State Key Laboratory of Electrical Insulation and Power Equipment,
Xi’an Jiaotong University, China (EIPE19123, EIPE18311), the Project of National Thousand
2
1

Journal of Materials Chemistry A
Page 22 of 26
View Article Online
DOI: 10.1039/C9TA03862K
3
3
3
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
87
88
89
90
91
92
93
94
95
96
97
98
99
00
01
02
03
04
05
06
07
08
Talents. TEM and SEM were carried out at the International Center for Dielectric Research (ICDR).
EDS mapping was carried out at the Analysis and Test Center of Xi’an Jiaotong University. We
thank Hu Nan, Yanzhu Dai, Chao Li for their help in using TEM, SEM and EDS, respectively.
References
1.
2.
3.
4.
5.
6.
7.
A. Fujishima and K. Honda, Nature, 1972, 238, 37-38.
Y. Ji and Y. Luo, J. Power Sources, 2016, 306, 208-212.
X. Liu, G. Dong, S. Li, G. Lu and Y. Bi, J. Am. Chem. Soc., 2016, 138, 2917-2920.
X. Pan and Y.-J. Xu, J. Phys. Chem. C, 2015, 119, 7184-7194.
Q. Xiang, J. Yu and M. Jaroniec, J. Am. Chem. Soc., 2012, 134, 6575-6578.
T. Xiong, W. Cen, Y. Zhang and F. Dong, ACS Catal., 2016, 6, 2462-2472.
H. Zhao, Y. Dong, P. Jiang, H. Miao, G. Wang and J. Zhang, J. Mater. Chem. A, 2015, 3, 7375-
7381.
8.
9.
X. Lu, K. Xu, P. Chen, K. Jia, S. Liu and C. Wu, J. Mater. Chem. A, 2014, 2, 18924-18928.
Y. Zou, J.-W. Shi, D. Ma, Z. Fan, L. Cheng, D. Sun, Z. Wang and C. Niu, ChemSusChem, 2018,
11, 1187-1197.
10.
11.
J. X. Li, C. Ye, X. B. Li, Z. J. Li, X. W. Gao, B. Chen, C. H. Tung and L. Z. Wu, Adv. Mater.,
2017, 29, 1606009.
Z. Chai, T.-T. Zeng, Q. Li, L.-Q. Lu, W.-J. Xiao and D. Xu, J. Am. Chem. Soc., 2016, 138,
10128-10131.
12.
13.
D. Ma, J.-W. Shi, Y. Zou, Z. Fan, X. Ji, C. Niu and L. Wang, Nano Energy, 2017, 39, 183-191.
T. Simon, N. Bouchonville, M. J. Berr, A. Vaneski, A. Adrović, D. Volbers, R. Wyrwich, M.
2
2

Page 23 of 26
Journal of Materials Chemistry A
View Article Online
DOI: 10.1039/C9TA03862K
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
09
Döblinger, A. S. Susha, A. L. Rogach, F. Jäckel, J. K. Stolarczyk and J. Feldmann, Nat. Mater.,
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
2014, 13, 1013.
14.
15.
16.
17.
S. Cao, C.-J. Wang, X.-J. Lv, Y. Chen and W.-F. Fu, Appl. Catal., B, 2015, 162, 381-391.
Q. Sun, N. Wang, J. Yu and J. C. Yu, Adv. Mater., 2018, 30, 1804368.
J. Zhang, J. Yu, Y. Zhang, Q. Li and J. R. Gong, Nano Lett., 2011, 11, 4774-4779.
D. Zeng, L. Xiao, W. J. Ong, P. Wu, H. Zheng, Y. Chen and D. L. Peng, ChemSusChem, 2017,
10, 4624-4631.
18.
19.
20.
21.
W. Xu, P. Ye, J. Iocozzia, H. Zhang, Y. Yuan and Z. Lin, J. Mater. Chem. A, 2017, 5, 21669-
21673.
N. Zhang, Y. Zhang, X. Pan, X. Fu, S. Liu and Y.-J. Xu, J. Phys. Chem. C, 2011, 115, 23501-
23511.
J. Zhang, Y. Wang, J. Jin, J. Zhang, Z. Lin, F. Huang and J. Yu, ACS Appl. Mat. Interfaces,
2013, 5, 10317-10324.
Q. Li, B. Guo, J. Yu, J. Ran, B. Zhang, H. Yan and J. R. Gong, J. Am. Chem. Soc., 2011, 133,
10878-10884.
22.
23.
M.-Q. Yang, C. Han and Y.-J. Xu, J. Phys. Chem. C, 2015, 119, 27234-27246.
L. Zhang, X. Fu, S. Meng, X. Jiang, J. Wang and S. Chen, J. Mater. Chem. A, 2015, 3, 23732-
23742.
24.
25.
G. Lin, J. Zheng and R. Xu, J. Phys. Chem. C, 2008, 112, 7363-7370.
J. Feng, J. Liu, G. Wei, J. Zhang, S. Wang, Z. Wang and C. An, RSC Adv., 2014, 4, 36665-
36670.
26.
D. Lang, Q. Xiang, G. Qiu, X. Feng and F. Liu, Dalton Trans., 2014, 43, 7245-7253.
2
3

Journal of Materials Chemistry A
Page 24 of 26
View Article Online
DOI: 10.1039/C9TA03862K
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
27.
28.
L. Xu-Bing, C.-H. Tung and L.-Z. Wu, Nature Reviews Chemistry, 2018, 2, 160-173.
J.-W. Shi, D. Ma, Y. Zou, Z. Fan, J. Shi, L. Cheng, X. Ji and C. Niu, J. Power Sources, 2018,
379, 249-260.
29.
30.
31.
D. Ma, J.-W. Shi, Y. Zou, Z. Fan, J. Shi, L. Cheng, D. Sun, Z. Wang and C. Niu, Nanoscale,
2018, 10, 7860-7870.
X. Zou, P.-P. Wang, C. Li, J. Zhao, D. Wang, T. Asefa and G.-D. Li, J. Mater. Chem. A, 2014,
2, 4682-4689.
J. Hou, C. Yang, H. Cheng, Z. Wang, S. Jiao and H. Zhu, Phys. Chem. Chem. Phys., 2013, 15,
15660-15668.
32.
33.
J. Zhang, L. Wang, X. Liu, X. a. Li and W. Huang, J. Mater. Chem. A, 2015, 3, 535-541.
Y.-P. Yuan, L.-W. Ruan, J. Barber, S. C. Joachim Loo and C. Xue, Energy Environ. Sci., 2014,
7, 3934-3951.
34.
35.
K. Chang, Z. Mei, T. Wang, Q. Kang, S. Ouyang and J. Ye, ACS Nano, 2014, 8, 7078-7087.
L. J. Zhang, R. Zheng, S. Li, B. K. Liu, D. J. Wang, L. L. Wang and T. F. Xie, ACS Appl. Mat.
Interfaces, 2014, 6, 13406-13412.
36.
Y. Ben-Shahar, F. Scotognella, N. Waiskopf, I. Kriegel, S. Dal Conte, G. Cerullo and U. Banin,
Small, 2015, 11, 462-471.
37.
38.
39.
Z. Sun, H. Zheng, J. Li and P. Du, Energy Environ. Sci., 2015, 8, 2668-2676.
W. Zhang, Y. Wang, Z. Wang, Z. Zhong and R. Xu, Chem. Commun., 2010, 46, 7631-7633.
X.-L. Yin, L.-L. Li, W.-J. Jiang, Y. Zhang, X. Zhang, L.-J. Wan and J.-S. Hu, ACS Appl. Mat.
Interfaces, 2016, 8, 15258-15266.
40.
J. Yang, H. Yan, X. Wang, F. Wen, Z. Wang, D. Fan, J. Shi and C. Li, J. Catal., 2012, 290,
2
4

Page 25 of 26
Journal of Materials Chemistry A
View Article Online
DOI: 10.1039/C9TA03862K
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
53
151-157.
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
41.
X. Zong, G. Wu, H. Yan, G. Ma, J. Shi, F. Wen, L. Wang and C. Li, J. Phys. Chem. C, 2010,
114, 1963-1968.
42.
43.
44.
45.
L. Jiang, L. Wang, G. Xu, L. Gu and Y. Yuan, Sustainable Energy Fuels, 2018, 2, 430-435.
Z.-R. Tang, F. Li, Y. Zhang, X. Fu and Y.-J. Xu, J. Phys. Chem. C, 2011, 115, 7880-7886.
B. Weng, S. Liu, N. Zhang, Z.-R. Tang and Y.-J. Xu, J. Catal., 2014, 309, 146-155.
R. M. Ma, L. Dai, H. B. Huo, W. Q. Yang, G. G. Qin, P. H. Tan, C. H. Huang and J. Zheng,
Appl. Phys. Lett., 2006, 89, 203120.
46.
47.
48.
J.-W. Shi, X. Zong, X. Wu, H.-J. Cui, B. Xu, L. Wang and M.-L. Fu, ChemCatChem, 2012, 4,
488-491.
J.-W. Shi, J.-W. Chen, H.-J. Cui, M.-L. Fu, H.-Y. Luo, B. Xu and Z.-L. Ye, Chem. Eng. J.,
2012, 195-196, 226-232.
D. Ma, J.-W. Shi, D. Sun, Y. Zou, L. Cheng, C. He, H. Wang, C. Niu and L. Wang, Appl. Catal.,
B, 2019, 244, 748-757.
49.
50.
J.-J. Miao, L.-P. Jiang, C. Liu, J.-M. Zhu and J.-J. Zhu, Inorg. Chem., 2007, 46, 5673-5677.
S. Kai, B. Xi, X. Liu, L. Ju, P. Wang, Z. Feng, X. Ma and S. Xiong, J. Mater. Chem. A, 2018,
6, 2895-2899.
51.
52.
53.
E. Hong, D. Kim and J. H. Kim, J. Ind. Eng. Chem., 2014, 20, 3869-3874.
G. Chen, F. Li, Y. Fan, Y. Luo, D. Li and Q. Meng, Catal. Commun., 2013, 40, 51-54.
D. Wang, T. Hisatomi, T. Takata, C. Pan, M. Katayama, J. Kubota and K. Domen, Angew. Chem.
Int. Ed., 2013, 52, 11252-11256.
54.
D. Ma, J.-W. Shi, D. Sun, Y. Zou, L. Cheng, C. He, Z. Wang and C. Niu, ACS Sustainable
2
5

Journal of Materials Chemistry A
Page 26 of 26
View Article Online
DOI: 10.1039/C9TA03862K
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
Chem. Eng., 2019, 7, 547-557.
55.
56.
57.
D. Jiang, Z. Sun, H. Jia, D. Lu and P. Du, J. Mater. Chem. A, 2016, 4, 675-683.
M. Xing, B. Qiu, M. Du, Q. Zhu, L. Wang and J. Zhang, Adv. Funct. Mater., 2017, 27, 1702624.
Q. Liang, Z. Li, Z. Huang, Hong, F. Kang, Q. Yang and Hong, Adv. Funct. Mater., 2015, 25,
6885-6892.
58.
59.
60.
61.
62.
63.
W. Li, C. Feng, S. Dai, J. Yue, F. Hua and H. Hou, Appl. Catal., B, 2015, 168-169, 465-471.
M. Cao, P. Wang, Y. Ao, C. Wang, J. Hou and J. Qian, Dalton Trans., 2015, 44, 16372-16382.
Z. Zhou, F. Han, L. Guo and O. V. Prezhdo, Phys. Chem. Chem. Phys., 2016, 18, 16862-16869.
D. Jing and L. Guo, J. Phys. Chem. B, 2006, 110, 11139-11145.
Y. Zhang, N. Zhang, Z.-R. Tang and Y.-J. Xu, ACS Nano, 2012, 6, 9777-9789.
J. Zhang, Y. Wang, J. Zhang, Z. Lin, F. Huang and J. Yu, ACS Appl. Mat. Interfaces, 2013, 5,
1031-1037.
64.
65.
H. Yan, J. Yang, G. Ma, G. Wu, X. Zong, Z. Lei, J. Shi and C. Li, J. Catal., 2009, 266, 165-
168.
J. Feng, C. An, L. Dai, J. Liu, G. Wei, S. Bai, J. Zhang and Y. Xiong, Chem. Eng. J., 2016, 283,
351-357.
66.
67.
F. Wang, Y. Su, S. Min, Y. Li, Y. Lei and J. Hou, J. Solid State Chem., 2018, 260, 23-30.
H. Zhao, Y. Dong, P. Jiang, G. Wang, H. Miao, R. Wu, L. Kong, J. Zhang and C. Zhang, ACS
Sustainable Chem. Eng., 2015, 3, 969-977.
68.
Y. P. Xie, Z. B. Yu, G. Liu, X. L. Ma and H.-M. Cheng, Energy Environ. Sci., 2014, 7, 1895-
1901.
2
6