Facile preparation of semimetallic WP2 as a novel photocatalyst with high photoactivity

Article abstract of DOI:10.1039/c5ra26269k

Searching for inexpensive and earth-abundant photocatalysts with high activities has attracted considerable research in recent years. In this work, semimetallic tungsten diphosphide (WP₂) micro-particles are explored as a novel photocatalyst for the first time. The WP₂ particles were synthesized through a solid-state reaction route via vacuum encapsulation technique following by water washing. The first principle calculations and electric transport measurements show a semimetallic characteristic of WP₂, however a strong absorption in the UV range is observed. The prepared WP₂ particles exhibit an admirable photocatalytic activity towards oxidation of methyl orange and reduction of water for H₂ evolution with the assistance of co-catalyst element Pt under UV light irradiation. Hydroxyl radicals detected by fluorescence spectroscopy in the solution in the presence of WP₂ under UV light irradiation confirms the photoactivity. Furthermore, the photocatalyst shows a good photostability and reusability even after three successive experiment runs. Based on the experimental measurements and theoretical calculations, a possible photocatalytic mechanism is proposed for semimetallic WP₂. The present study may provide a chance for practical applications of the semimetallic material WP₂ in the field of photocatalysis.

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DOI: 10.1039/C5RA26269K
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ARTICLE
Facile Preparation of Semimetallic WP2 as a Novel Photocatalyst
with high photoactivity
Mingyu Pi, a Tianli Wu, a Dingke Zhang, b Shijian Chen a,* and Shuxia Wang a
Received 00th January 20xx,
Accepted 00th January 20xx
DOI: 10.1039/x0xx00000x
Searching for inexpensive and earth-abundant photocatalysts with high activities has attracted considerable research in
recent years. In this work, semimetallic tungsten diphosphide (WP2) micro-particles are explored as a novel photocatalyst
at the first time. The WP2 particles were synthesized through solid-state reaction route via vacuum encapsulation
technique following by water washing. The first principle calculations and electric transport measurements show a
semimetallic characteristics of WP2, however a strong absorption in the UV range is observed. The prepared WP2 particles
exhibit an admirable photocatalytic activity towards oxidation of methyl orange and reduction of water for H2 evolution
with the assist of co-catalyst element Pt under UV light irradiation. Hydroxyl radical detected by fluorescence spectroscopy
in the solution in the presence of WP2 under UV light irradiation confirms the photoactivity. Furthermore, the
photocatalyst shows a good photostability and reusability even after three successive experiment runs. Based on the
www.rsc.org/
experimental measurements and theoretical calculations,
a possible photocatalytic mechanism is proposed for
semimetallic WP2. The present study provides a chance for practical applications of semimetallic material WP2 in the field
of photocatalysis.
range.13-14 g-C3N4 as a metal-free photocatalyst can also evolve
hydrogen from water even without the decoration of the
Introduction
Global energy and environment crisis is a big challenge that
every country has to face to, intensive research interest has
been devoted to searching for active photocatalysts to solve
this crisis. Among which photocatalytic conversion of solar
energy has been attracting worldwide attention.1-3 In the past
noble metals.15 The reported photocatalysts are mostly
semiconductors, which have been exclusively studied with
respect to photocatalytic applications. Generally, the electron-
hole pairs generated from the light absorption across the band
gap between the valence band (VB) and conduction band (CB)
which subsequently migrate to the surface of semiconductors
to participate in the redox reactions.16 Nevertheless, metallic
materials differ from semiconductors for the lack of band gap
to separate occupied and unoccupied levels, as a result, these
materials are believed meaningless for photocatalytic
applications due to the fast recombination of the photo-
generated electron-hole pairs.
decades, semiconductor photocatalysis, as
a
“green”
technology, has been widely used for the degradation of
organic dye, hydrogen evolution from water and removal of
toxic gases.4-5 Along this lines, hundreds of materials have
been investigated as the potential photocatalysts, including
oxides, sulfide, nitrides and phosphates. For example, for the
high photocatalytic efficiency and photostability, TiO2 is the
most widely used and studied photocatalyst so far.6-10 The
other photocatalysts were also prepared, such as Ni decorated
CdS nanorods enhanced the photocatalytic hydrogen evolution
under a redox shuttle mechanism.11 Cu2O microcrystals are
found to perform efficiently in hydrogen generation and
formaldehyde degradation at room temperature.12 Ag3PO4
with high photocatalytic activity and Cu2(OH)PO4 exhibiting
promising photocatalytic properties in the near infrared
However, as
a
new and unconventional class of
photocatalysts with the application potential, metallic
materials have been discovered. For example, Sr1-xNbO3 was
discovered as an active metallic photocatalyst by Irvine et al,17
and they demonstrated that metallic perovskite oxides
facilitate kinetic charge separation which is effective in
degrade methylene blue, as well as in hydrogen and oxygen
evolution from water. Black bismuth was also reported as
semimetal photocatalyst for NO oxidation in air.18 And most
recently, transition metal phosphide MoP2 was discovered as a
semimetallic photocatalyst with high photoactivity to
efficiently decompose methyl orange and produce hydrogen
from water.19 The above semimetallic materials have the
unusual electronic properties which result from its small
electron effective mass, large mean free path and so on. And
a.School of Physics, Chongqing University, Shapingba, Chongqing 401331, P.R.
China
b.College of Physics and Electronic Engineering, Chongqing Normal University,
Shapingba, Chongqing 401331, P.R. China
Electronic Supplementary Information (ESI) available: Temperature dependence
electrical resistivity and mechanism of hydrogen evolution of WP2. See
DOI: 10.1039/x0xx00000x
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high carrier mobility in these materials may allow effective element red phosphorus were uniformly mixed and vacuum-
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separation of carriers, especially if the carrier can be rapidly sealed (~ 7×10-4 Pa) in a silica tube. Then, the tube was put
DOI: 10.1039/C5RA26269K
transferred.18These discoveries provide a new perspective for into a muffle furnace which was heated to 950 oC in 95
photocatalyst screening and a direction to search for novel minutes and kept at this temperature for 5 h. Then the furnace
photocatalysts with metallic behaviors.
Transition-metal phosphides are an important class of sample was collected from the silica tube. The powders sample
compounds with metalloid characteristics and good electrical are black particles mixed with few white particles.
was cooled down to room temperature naturally. Powders
a
conductivity,20which are studied as highly efficient Considering the fact that the white particles are reliable to
electrocatalyst, such as MoP, WP, FeP, CoP, Cu3P, 20-24 but the deliquesce in air, we believe that they are side product of P2O5.
photocatalytic properties of these materials have not been After washed the powders by water for several times the
intensively studied. We recently reported that MoP2 as a impurities P2O5 were successfully removed. After the washing
semimetallic photocatalyst towards decomposing methyl treatment, the sample was dried under 60 oC in a vacuum oven
orange and producing hydrogen from water.19 Analogy to for 12 hours.
transition metal phosphide MoP2, WP2 has the same
Photocatalytic degradation experiment
orthorhombic crystal structure and a similar band structures
with MoP2 in which the VB and CB overlap at the Fermi level,
indicating a semimetallic property, which is consistent with the
early article, 25 and the property was experimentally confirmed
by the electrical resistivity measurements in this work. WP2
The photocatalytic degradation activities of the synthesized
WP2 sample were examined by monitoring the photocatalytic
degradation of methyl orange (MO) in aqueous solution under
UV light irradiation. The light source for photocatalysis was a
high pressure mercury lamp, which provided the UV light. The
experiments were carried out at room temperature in order to
eliminate temperature effects. In each experiment, a certain
amount of WP2 photocatalyst were added into 50 mL MO
solution with a concentration of 5 mg/L. Prior to irradiation,
the suspensions were magnetically stirred in dark for 30
minutes to achieve adsorption equilibrium between the MO
molecules and the photocatalyst. During the light irradiation
process, the suspensions were periodically withdraw,
centrifuged to separate the photocatalyst and used for
absorbance measurements by a UV-Vis spectrophotometer. A
blank test was also carried out on an aqueous MO solution
without photocatalyst under the same light irradiation
condition to evaluate the efficiency of the photocatalyst.
26
was first synthesized by S. Rundqvist et al in 1963 through
the reaction of element tungsten and red phosphorus. This
traditional method needs to cost much energies for reaction at
o
a very high temperature of 1100 C and a very long reaction
27
time of several days. Very recently, Li et al synthesized WP2
nanorods with excellent performance as an efficient hydrogen
evolution reaction electrocatalys. The WP2 nanorods were
synthesized through phosphidation of (NH4)0.25WO3 nanorods
precursor which were prepared by complicated chemical
methods.
In this work, we develop a cheap and conventional method
to synthesize WP2 particles. Namely, simple solid-state
reaction of WO3 and red phosphorus can synthesize high
crystalline WP2 particles. The obtained WP2 particles were
explored the photocatalytic properties which, to our best
knowledge, has not been reported before. The results show
that WP2 particles can efficiently photodegrade the methyl
orange (MO) and evolve hydrogen from water and has a good
photostability and reusability, indicating the potentials as a
new photocatalyst. The photoactivities of the sample are
confirmed by the detection of the existence of the hydroxyl
radical by fluorescence spectroscopy in solution in the
presence of WP2 under UV light irradiation. Based on the
experimental measurements and theoretical calculations, a
possible photocatalytic mechanism is proposed.
Photocatalytic H2 production
The hydrogen generation reactions of the WP2 photocatalyst
were carried out in an outer irradiation-type photoreactor
connected to a closed gas-circulation system. Typically, 70 mg
of WP2 photocatalyst were added into 50 mL solution
containing 20 vol% triethanolamine (TEA) as a sacrificial
reagent to capture the photo-generated holes. 2 wt% Pt were
loaded on the surface of the WP2 photocatalyst by the in situ
photo-deposition method using H2PtCl6. The top of the reactor
was tightly closed by a silica rubber. A 350 W high pressure
mercury lamp was applied as the UV light source, which was
positioned above the side of the photo-reactor. The WP2
photocatalyst were continuously dispersed in the aqueous TEA
solution by a magnetic stirrer during the light irradiation. The
photocatalytic reaction was performed at room temperature.
The photocatalytic H2 evolution rate was analysed by gas
chromatograph (GC9790II, FULI) with thermal conductivity
detector.
Experimental Section
Synthesis of WP2 photocatalyst
All the purchased and used chemical reagents were analytical
grade without further purification. The WP2 particles were
prepared by solid-phase reaction in evacuated and sealed silica
tubes at a certain reaction temperature. Tungsten trioxide
(WO3) and element red phosphorus (P) were used as the
tungsten and phosphorus sources, respectively. The reaction
details are as follows: 0.5 g tungsten trioxide and 0.3 g
Trapping experiment of hydroxyl radicals (●OH)
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Fig. 1 (a) XRD patterns and (b) crystal structure of the
synthesized WP2.
During the photocatalytic degradation reaction, the ●OH
formed on the surface of the irradiated photocatalyst was
detected by the fluorescence technique using terephthalic acid
(TA) as a probe molecule. In a brief experimental procedure,
70 mg of WP2 photocatalyst were dispersed in 50 mL of a
mixture of a 5×10-4 mol/L aqueous TA solution and a 2×10-3
mol/L NaOH solution. The resulting solution was magnetically
stirred and the suspension was exposed to the light. At a
certain time intervals, the suspensions was collected and
centrifuged to measure the maximum fluorescence intensity
using the fluorescence spectrophotometer with an excitation
wavelength of 315 nm.
Fig. 2 (a) Typical FE-SEM image, (b) the magnified SEM
image of the WP2 particles, (c) EDX and (d) HRTEM image
of the WP2 photocatalyst.
The crystal structure and phase purity of the sample were
characterized by XRD. Fig. 1a shows the XRD patterns of the
WP2 sample, which was synthesized via a solid-phase reaction
method at the reaction temperature of 950 oC for 5 hours
followed with water washing to remove the impurities P2O5.
The diffraction peaks can be indexed to the typical peaks of
WP2 (space group: Cmc21, JCPDS card no. 76-2364), and the
sharp and strong diffraction peaks indicate that the obtained
product is high crystalline. The crystal structure of the WP2 is
shown in Fig. 1b, which corresponds to the orthorhombic
structure and the lattice constants are a=3.1649, b=11.1599
and c=4.9732 Å, respectively. It should be noted that no other
peaks related to any impurities phase are observed, which
indicates that the obtained WP2 sample is with a high purity.
Theoretical calculations
All the calculations were performed at the generalized
gradient approximation function of the Perdew-Burke-
Ernzerhof form28 with the projector-augment wave potential
29
implemented in the simulation package VASP. The cut-off
energy for the plane wave was chosen to be 500 eV, with
10×10-5 eV per atom for SCF tolerance. Monkhorst-Pack k-
points were set to be 5×5×5. The electronic structures were
calculated based on the fully relaxed lattice parameters and
ionic positions. For the calculation of the density of the states
(DOS), a large 7×7×7 k-points set was used.
Comparing with the reaction of element tungsten with red
26
phosphorus
and phosphidation of (NH4)0.25WO3 nanorods
precursor, 27 our method of simple solid-state reaction of WO3
and red phosphorus is convenient and much efficient.
The morphology of the prepared WP2-based photocatalyst
was characterized by the field emission scanning electron
Characterization
The crystal structures of the samples were obtained by X-ray
diffractometer (Rigaku D/MAX2500PC) with Cu Kα radiation
(1.54 Å). Diffraction angle (2-theta) ranges from 5° to 90° and
the scanning rate is 4° / min. The field emission scanning
electron microscopy (FE-SEM, TESCAN MIRA 3) with an energy
dispersive X-ray spectrometer (EDX) and a transmission
electron microscopy (TEM, ZEISS Libra 200FE) were employed
for the morphological observation, the size, and structure of
the samples. The absorption at about 465nm were conducted
to identify the concentration of MO by using a UV-Vir
spectrophotometer (Shimadzu UV-3600). The fluorescence
measurements were recorded on a Hitachi F4500 fluorescence
spectrophotometer at an excitation wavelength of 315 nm.
Fig. 3 UV-vis absorption spectra of the WP2-based
photocatalyst. Inset: the corresponding Kubelka –
Munk transformed spectrum.
Results and Discussion
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Fig. 4 Calculated electronic band structure (left) and
DOS (right) of WP2.
Fig. 5 Schematic band structure and transition
mechanism of WP2.
microscopy (FE-SEM). Fig. 2a shows that the obtained WP2
samples are composed of particles with the size of about 2-3
micrometers. Fig. 2b shows the magnified SEM image of the
sample, it can be observed that the WP2 particles have a lotus
root-like structure with smooth surface. Energy dispersive X-
ray spectrometer (EDX) measurement as shown in Fig. 2c
shows that the atomic ratio of W: P is about 1: 2.11, which is
consistent with the stoichiometric composition of the pure
WP2. The transmission electron microscopy (TEM) image was
provided for further insight into the microstructure of the
obtained product as shown in Fig. 2d. The observed lattice
fringes with a d-spacing of 0.342 nm and 0.305 nm in the high-
resolution TEM image match well with the (021) and (110)
crystal plane distances of WP2, which also shows that high
crystalline WP2 particles are synthesized.
overlap at the Fermi level, so the strong absorption observed
in the UV range in Fig. 3 cannot be explained by the traditional
transition mechanism that the electrons transition from the
occupied VB to the unoccupied CB. This phenomenon was also
18-19
observed from semimetal Bi and MoP2,
and the observed
band gap was assigned the transition from the occupied level
to the valence band. Along this line, we describe the band
structure and transition mechanism of WP2 in Fig. 5. From the
calculation results, we can see that an indirect transition from
the subbands blow the VB to VB (Fig. 4) can be possible under
UV light excitation. B1 and B-1 depict the bands above the CB
and blow the VB, respectively, as shown in Fig. 5. According to
the model, the observed band gap energy can be assigned to a
B-1 to VB transition from an occupied level to the valence band.
Here, we should know that the calculated value is smaller than
the experimental value as the result of the well know band gap
underestimation within the framework of standard DFT.18
The photocatalytic activities of the synthesized WP2 sample
were evaluated for the degradation of MO under UV light
irradiation. Fig. 6a shows the degradation efficiency for MO
varies with different dosage of WP2 photocatalysts. The
degradation efficiency of MO is 78%, 92%, 100%, 100% for the
WP2 dosage of 30, 50, 70, 90 mg, respectively, from which we
can see that the MO is completely degraded with the dosage is
70 mg, when increased the dosage of the ptotocatalyst
furthermore, the change of the degradation efficiency of MO is
not obvious. In the view of the degradation efficiency and the
saving of the ptotocatalyst, we selected 70 mg as the best
dosage of WP2 for the degradation reaction. Fig. 6b shows the
The optical property of the as-prepared WP2 photocatalyst
was studied by UV-vis absorption spectra, the result is shown
in Fig. 3. The band gap energy of WP2 can be estimated from
the following equation: 30-31
αhν = A ( hν-Eg)n/2
Where α, h, ν and Eg are the absorption coefficient, Plank´s
constant, light frequency, and the band gap energy,
respectively, and A is a constant. The factor n depends on the
characteristics of the optical transition of a semiconductor
(n=1 for direct transition and n=4 for indirect transition). The
inset shows the corresponding Kubelka-Munk transformed
spectrum, from which we can obtain that the band gap energy
is about 3.42 eV.
In order to study the electronic structure of the as-prepared
WP2 photocatalyst, we conducted first-principle calculations of
the band structures and density of states (DOS) for the crystal
WP2, which are shown in Fig. 4. The Fermi level was set as Ef=0.
The calculated results show that the Fermi level is located in
the overlap region between the bottom of the CB and the top
of the VB, which indicates a semimetallic behavior. The
electrical resistivity measurements show a linear dependence
of the temperature and a slow increase in the resistivity with
the temperature increases, which also confirms the metallic
characteristics of WP2 (Fig. S1†). Unlike the band structure of
well-described typical semiconductors, the VB and CB of WP2
Fig. 6 (a) the degradation efficiency of MO with different
dosage of photocatalyst, (b) photocatalytic degradation of
MO in aqueous solution under UV light irradiation.
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Fig. 7 (a) Reusability of the WP2-based photocatalyst for
photocatalytic degradation of MO in aqueous solution (b)
XRD patterns of the photocatalysts before and after the
photocatalytic reaction.
Fig. 8 Hydroxyl radicals (●OH) trapping fluorescence
photo-degradation progress of MO under UV light irradiation
with the optimized dosage. About 10% decrease of
concentration of MO when the dark adsorption equilibrium
achieved, the weak adsorptive capacity can be ascribed to a
relatively large size with smooth surface of WP2 particles. But
nearly 100% of the dye is degraded in 100 minutes after
turning on the light. A blank experiment (without photoctalyst)
was also conducted, the MO was stable under UV light
irradiation, which indicates that the degradation of MO was
the result of WP2 photocatalyst. As we know, MO, a typical dye
which is hard to degrade, various photocatalysts were studied
to remove MO.32-35 Comparing with the most of reported
photocatalysts, our WP2 particle photocatalyst offers a good
photoactivity.
spectra of WP2-based photocatalyst in terephthalic
acid (TA) solution under UV light irradiation.
irradiation. The maximum intensity peaks in the PL spectra are
observed at approximately 428 nm with an excitation
wavelength of 315 nm, demonstrating that ●OH is formed on
the UV light irradiated surface of the WP2-based photocatalyst
in the photocatalytic oxidation process, which is in agreement
with the early articles.19,36 It also can be observed that the PL
intensity increase gradually with increasing the light irradiation
time, which indicates that TAOH accumulates in the solution
and the accumulation increases continuously. The existence of
●OH in the solution in the presence of WP2 under UV light
irradiation confirms the photocatalytic activity of WP2.
The photostability and reusability of the photocatalyst are
also very important for practical application. To evaluate the
stability and reusability of the WP2 photocatalyst, three
successive photocatalytic experiment runs were carried out by
adding recycled WP2 photocatalyst to fresh MO solutions with
no change in the overall concentration of the catalyst under
UV light irradiation. As shown in Fig. 7a, the photocatalytic
activity of WP2 for the degradation of MO does not obviously
change after the recycle runs under the same experiment
conditions. Furthermore, the XRD pattern of the WP2
photocatalyst after the reaction has no obvious change
comparing with the sample before the reaction as shown in Fig.
7b. The above results indicate that the as-synthesized WP2
photocatalyst has excellent photostability and reusability for
the practical applications.
During the photocatalytic process, the photo-generated
electrons will join in the multistep reduction of dissolved O2 to
generate hydroxyl radicals (●OH), and the photo-generated
holes will oxidize the H2O molecules to generate ●OH. The
●OH, known as a primary oxidant with strong oxidability in the
photocatalytic system, can degrade the organic dye into H2O
and CO2, so the generation of ●OH is important for the
photocatalytic reaction, and the existence of ●OH can confirm
the photocatalytic activity of the photocatalyst. The ●OH
generated during the photocatalytic reaction can be easily
detected by a fluorescence technique using terephthalic acid
(TA) as a probe molecule, the TA can reacts with ●OH to
produce the highly fluorescent product, 2-hydroxyterephthalic
acid (TAOH).36 Fig. 8 shows the ●OH trapping PL spectra of
WP2-based photocatalyst in TA solution under UV light
The possible mechanism for the photocatalytic degradation
of MO: Based on the above experimental and theoretical
results, a possible photocatalytic mechanism of WP2 is
proposed which bases on the conventional mechanism of
semiconductor photocatalysts. Combined the band gap energy,
we can obtain the absolute energies of the CB and VB of WP2
according to the following two equations: 30
EVB = χ - Ee + 1/2 Eg
(a)
(b)
ECB = EVB - Eg
Where χ is the absolute electronegativity of WP2 (~5.18 eV), Ee
is the normal hydrogen electrode scale to the absolute vacuum
scale (~4.5 eV) and Eg is the band gap energy of WP2 (~3.42 eV).
Based on the above parameters, the absolute energies of CB
and VB are -1.03 eV and 2.39 eV, respectively.
Fig. 9 The possible schematic illustration of the
photocatalytic reaction of WP2 for the degradation of
MO in aqueous solution under UV light irradiation.
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Conclusions
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DOI: 10.1039/C5RA26269K
In summary, high crystalline tungsten diphosphide (WP2)
particles were facile synthesized by solid-phase reaction of
WO3 and red phosphorus in evacuated and sealed silica tube.
WP2 is explored as a new photocatalyst which can efficiently
photodegrade the methyl orange and evolve hydrogen from
water under UV light irradiation and with a good photostability
and reusability. The detection of the existence of the hydroxyl
radical by fluorescence spectroscopy in solution in the
presence of WP2 under UV light irradiation confirms its
photoactivity. Based on the experimental measurements and
theoretical calculations, a possible photocatalytic mechanism
is proposed. Therefore, this work provides a chance for
practical applications of semimetallic material WP2 in the field
of photocatalysis.
Fig. 10 Hydrogen evolution rate of WP2 and 2%
Pt- WP2.
The possible photocatalytic mechanism of WP2 is shown in
Fig. 9, and the photocatalytic reactions are described as
follows:
Acknowledgements
This work is supported by the National Natural Science
Foundation of China (NSFC) (grants 11304406 and 61307035).
WP2+hν→e-(WP2) + h+ (WP2)
(1)
(2)
(3)
(4)
(5)
(6)
-
e- + O2→●O2
-
●O2 + 2e- +2H+→●OH + OH-
Notes and references
2H2O+2h+→H2O2+2H+
H2O2+e-→●OH + OH-
MO+●OH→H2O+ CO2
1
2
3
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The electrons migrate from B-1 to VB under the UV light
irradiation, leaving holes behind (equ. 1). The photo-generated
electrons reduce the O2 absorbed on the surface of the WP2
catalyst into ●OH (equ. 2 and 3). Meanwhile, the left holes
oxidize the H2O into ●OH (equ. 4 and 5).37-38 The ●OH will
finally degrade the MO into H2O and CO2 (equ. 6).
7
8
9
The photocatalysis technology consists of photocatalytic
degradation and water splitting for hydrogen evolution, so the
photocatalytic hydrogen evolution activity of the as-
synthesized WP2 product is therefore investigated. The result
shows that the WP2-based photocatalyst could achieve H2
production from water containing TEA as the sacrificial
electron donor under the UV light irradiation, and a control
experiment shows no H2 production in the dark environment
or without the catalyst, which indicates that the WP2 sample
plays a role as the photocatalyst under the light irradiation.
The schematic illustration of hydrogen evolution of WP2 are
shown in Fig. S2†. Usually, loading of a small amount of noble
metal (Pt) on the photocatalyst is used to improve the H2
production in photocatalytic reaction.39-41 As shown in Fig. 10,
the hydrogen evolution rate of the bare-WP2 is 3 μmolh-1g-1,
10 J. H. Choy, H. C. Lee, H. Jung and S. J. Hwang, J. Mater. Chem.,
2001, 11, 2232.
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and that is
8
μmolh-1g-1 for 2wt% Pt decorated WP2
photocatlyst, which is about 2.7 times of the bare-WP2.
Although the hydrogen evolution rate is not high comparing
with the other semiconductor catalysts, WP2 shows promising
and potential in application of the photocatalysis. Further work
about the photocatalysis of WP2 are under studied.
18 Q. Zhang, Y. Zhou, F. Wang, F. Dong, W. Li, H. Li and G. R.
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6 | J. Name., 2012, 00, 1-3
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