Tailoring the Porosity in Iron Phosphosulfide Nanosheets to Improve the Performance of Photocatalytic Hydrogen Evolution

Article abstract of DOI:10.1002/cssc.201900789

Metal sulfide photocatalysts are typically required during water splitting to produce hydrogen. However, the rapid recombination of photogenerated electron–hole pairs in these highly unstable photocatalysts has restricted hydrogen production to small-scale batch reactions. In this work, porous transition-metal thiophosphites were used to enable continuous long-term hydrogen production through photocatalysis. A wide bandgap (2.04 eV) was essential for generating hydrogen at a rate of 305.6 μmol h^?1 g^?1, 180 % faster than nonporous FePS₃ nanosheets. More importantly, the high in-plane stiffness of these approximately 7 nm thick porous FePS₃ nanosheets ensured structural stability during 56 h of continuous photocatalysis reactions. The reaction results with D₂O instead of H₂O indicated that hydrogen mainly came from H₂O. Furthermore, a sacrificial reagent (triethylamine) was photodegraded into diethylamine and acetaldehyde through a monoelectronic oxidation process, as indicated by HPLC and LC–MS. This synthesis strategy reported for FePS₃ porous nanosheets paves a new pathway for designing other dianion-based inorganic nanocrystals for hydrogen energy applications.

Full text of DOI:10.1002/cssc.201900789

Accepted Article
Title: Tailoring the porosity in iron phosphosulfide nanosheets to
improve performance of photocatalytic hydrogen evolution
Authors: Jian Zhang, Fang Feng, Yong Pu, Xing-Ao Li, Cher Hon Lau,
and Wei Huang
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To be cited as: ChemSusChem 10.1002/cssc.201900789
Link to VoR: http://dx.doi.org/10.1002/cssc.201900789
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ChemSusChem
Tailoring the porosity in iron phosphosulfide nanosheets to
improve performance of photocatalytic hydrogen evolution
Jian Zhang,[a],[b] Fang Feng,[b] Yong Pu, [a]
[a],[b] Cher Hon Lau,[c] and Wei Huang*[b],[d]
more active for photocatalytic water splitting. This is due to their
better photoresponse range. However, sulfide semiconductors
are susceptible to photo-corrosion (S2- + h
S) and hence are
highly unstable.[22,23] This can be overcome by rapid depletion or
migration of photogenerated holes on the valence band of
catalysts.
A new class of layered metal phosphorus trichalcogenides
with a general formula MPX3 (M = Fe, Mn, Ni, Cd, Zn; X = S or
Se) have attracted increasing attentions recently.[24,25] The metal
atom of these layered structures is typically sandwiched
between chalcogen atoms, forming an in-plane X-M-X
configuration. This is beneficial for the hydrogen evolution
reaction (HER) as the ratio of exposed chalcogen atoms i.e.
active hydrogen production sites is enhanced.[24,26-28]
A
distinctive characteristic of MPX3 structures is the wide-range
band gap that can also be exploited for optoelectronic
[29]
applications in a broad wavelength range.
Wang et. al.
synthesized NiPS3 photocatalyst nanosheets (a few atomic layer
thick) and employed these materials to produce hydrogen under
sunlight without using any sacrificial reagents.[30] Likewise
MnPS3, MnPSe3 nanosheets,[31] and monolayer FePS3 quantum
sheets,[32] these ultrathin NiPS3 nanosheets are highly unstable
due to drastic losses in catalytic activity after long-term batch
hydrogen generation. Clearly, the morphology and size of MPS3
nanosheets can significantly impact on the behavior of photo-
generated charge carriers.
Introduction
The conversion of solar energy into chemical energy can be
achieved by splitting water into hydrogen using efficient
photocatalysts derived from abundant earth-metals.[1-3] However,
most photocatalysts suffer from the rapid recombination of
photogenerated electron-hole pairs within 10 ns, drastically
limiting hydrogen production in small scale batch reactions.[4,5]
To overcome this drawback, strategies such as metallic or non-
metallic element doping,[6-8] heterojunction construction,[9-11] and
co-catalyst merging[12-14] have been developed to increase the
separation and migration efficiency of charge carriers during
photocatalytic hydrogen generation. Compared to traditional
oxide photocatalysts such as TiO2,[15] ZnO,[16] WO3,[17] Fe2O3,[18]
BiVO4,[19] BiFeO3,[20] ZnGa2O4,[21] sulfide semiconductors are
Enlightened by this observation, here we synthesized FePS3
porous nanosheets (PNSs) with uniform topography using our
previously-reported one-step sulfurphosphidation method.[33]
When compared to non-porous i.e. smooth FePS3 nanosheets,
the porosity of our novel structure was crucial for enhancing
photocatalytic hydrogen production rates by 180 %, reaching
305.6 mol h-1 g-1. This was ascribed to the generation of
hydrogen bubbles on rougher catalyst surfaces, which radically
increased
the
efficiency.[34]
Crucially,
the
enhanced
photocatalytic activity of these novel structures was maintained
even after continuous, long-term operation. Besides,
mechanistic studies on the role of sacrificial reagents were
performed. This unprecedented work potentially showcases a
facile, universal synthesis protocol for 2D metal phosphosulfide
nanosheets while setting a feasible criterion to evaluate the
practicability of photocatalysts for hydrogen evolution.
[a]
[b]
Dr. J. Zhang, Y. Pu, Prof. X. Li
New Energy Technology Engineering Lab of Jiangsu Province,
School of Science, Nanjing University of Posts &
Telecommunications (NUPT), Nanjing 210023, P. R. China.
E-mail: lxahbmy@njupt.edu.cn
Dr. J. Zhang, Ms. F. Feng, Prof. X. Li, Prof. W. Huang
Key Laboratory for Organic Electronics and Information Displays &
Institute of Advanced Materials (IAM), Jiangsu National Synergetic
Innovation Center for Advanced Materials (SICAM), Nanjing
University of Posts & Telecommunications, Nanjing 210023, P. R.
China.
2. Results and Discussion
[c]
[d]
Dr. C. Lau
2.1. Morphology of nanomaterials
University of Edinburgh, School of Engineering, Robert Stevenson
Rd, Kings Building, Edinburgh EH9 3FB, Midlothian, Scotland.
Prof. W. Huang
Shaanxi Institute of Flexible Electronics, Northwestern Polytechnical
University, 127 West Youyi Road, Xi'an, 710072, Shaanxi, P. R.
China.
E-mail: iamwhuang@njupt.edu.cn
Supporting information for this article is given via a link at the end of
the document.
SEM and TEM micrographs in Figure 1 clearly demonstrated the
differences in shape, size and porosity between smooth and
porous FePS3 nanosheets. Macroscale or quantum sheets of
MPX3 structures are typically produced by complex techniques
that require expensive and sophisticated equipment such as
chemical vapor transport[35] and methods that are difficult to
control i.e. liquid exfoliation.[32] Contrarily, our
7 nm-thick
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10.1002/cssc.201900789
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uniformly-shaped FePS3 nanosheets (NSs) with length ~50 nm
could be produced using a facile sulfur-phosphidation approach.
The only morphological difference between the smooth and
porous FePS3 NSs was the presence of tiny dark spots in the
porous nanomaterials. The morphologies including thickness
and porosity of both the FePS3 PNSs ans NSs were validated by
TEM micrographs (Figure 1c,d). We observed uniformally
structured distinctive lattice fringes of FePS3 (PNSs) with a
spacing of 0.32 nm resulting from the (002) plane of FePS3.[36]
The XRD spectra of both the FePS3 NSs and PNSs contained
all peaks corresponding to the standard card of FePS3 (JCPDS
Card No. 30-0663),[37] indicating the high crystalline and phase
purity of our synthesized nanocatalysts. An intense diffraction
peak located at 13.8° along with three weak peaks at 27.8°, 42.5°
and 57.6° could be indexed to (001), (002), (003), and (004)
planes of FePS3, respectively. Porosity in FePS3 nanosheets did
not cause any peak shifts i.e. the crystallinity of FePS was
3
retained even after different sulfur-phosphidation process.
Compared to the smooth samples, the diffraction peaks of
porous FePS3 nanosheets exhibited similar features but with
lower intensities (Figure 2a, red curve). Raman scattering
spectra obtained with an excitation wavelength of 532 nm
revealed that vibrational bonding in both FePS3 NSs and PNSs
were identical. We observed two sets of Raman mode vibrations
that could be attributed to the Fe and P2S6 components of the
FePS3 crystal system. As reported elsewhere,[38] peaks centered
STEM-HAADF and EDS mapping analyses indicated
a
homogeneous distribution of Fe, S, and P throughout the FePS3
NSs and PNSs, verifying the alloy composition of the ternary
system (Figure 1e and f). From Figure 1f, we also observed the
presence of pores in FePS3 (PNSs). Meanwhile, EDS mapping
spectrum also revealed that the atomic ratio of Fe : P : S was
close to 1 : 1 : 3, suggesting that the precise elemental
composition ratio of this nanomaterial was identical to FePS3.
Besides, EDS (Figure S1) and ICP-AES (Figure S2) results also
confirm the similar element content of FePS3.
1
at 588, 375, 279, 245, and 216 cm could be assigned to the
3
2
Eg , A1g2, Eg , A1g1, and Eg1 modes of FePS3 (Figure 2b). The Eg
1
2
3
modes (Eg , Eg , and Eg ) represented in-plane vibrations of the
P2S6 unit (tangential vibration of the P-P bond). Meanwhile,
intra-layer modes underpinned a slight Raman shift in thinner
structures, causing the observed shifts in both peak positions
(Figure 2b).[38] The sharp features in Raman spectra also
suggested that both the FePS3 NSs and PNSs could retain a
stable structure.[25]
Figure 2. (a) XRD patterns, and (b) Raman spectra of as-synthesized FePS3
NSs (black) and PNSs (red). (c) The N2 adsorption-desorption isotherm, and
pore-size distribution curves of (d) as-synthesized FePS3 NSs and PNSs.
The specific surface areas of FePS3 nanosheets studied here
were determined from N2 adsorption desorption isotherms
(Figure 2c). We observed a type IV isotherm at high relative
pressure (P/P0) and a H1 hysteresis loop in the relative pressure
range of 0.66-0.98 P/P0, implying the presence of mesopores.
The Brunauer-Emmett-Teller (BET) specific surface area of the
FePS3 PNSs was about 91.2 m2 g-1 nearly twice as large as
that of smooth FePS3 nanosheets (46.6 m2 g-1). The porosity
Figure 1. SEM micrographs of FePS3 NSs (a) and PNSs (b). TEM images of
FePS3 NSs (c) and PNSs (d). Inset of d: HRTEM image of the FePS3 PNSs.
Scanning transmission electron microscopy in high angle annular dark field
(STEM-HAADF) and energy dispersive spectroscopy (EDS) mapping (e and f)
micrographs of FePS3 NSs and PNSs, respectively.
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10.1002/cssc.201900789
ChemSusChem
within each finely dispersed nanosheet was key to doubling the
BET surface area. From the Barrett-Joyner-Halenda (BJH)
method, we observed a broad (1 40 nm), trimodal pore size
distribution in FePS3 porous nanosheets. Main of these peaks
were centered at 2.0, 6.8 and 18.6 nm, which was in good
agreement with TEM characterization (Figure 2d). The dominant
large pores were formed by the merger of numerous
interconnected small pores during thermal treatment, while
micropores that were beneficial for increasing the amount of
photocatalytic active sites were formed from the release of CO2
and H2O during decomposition of the Fe2(CO3)(OH)2 precursor
in the preheating phase (400 °C for 2 h).[39] As expected, for
These peaks were due to the spin-orbit split 2p3/2 (Ni-S) and
2p1/2 (P-S) binding energies, respectively.
The absorption properties of FePS3 samples were measured
with UV/vis diffuse reflectance absorption and ultraviolet
photoelectron spectroscopy (UPS). At both visible and UV light
ranges, a broad absorption peak was present in FePS3 NSs
(Figure 4a, black curve). Porosity in FePS3 nanosheets
intensified light absorption, especially in the UV range. This
absorption enhancement also underpinned better solar energy
conversion efficiences in other mesoporous or porous
photocatalysts by maximizing light adsorption.[44] According to
the Kubelka-Munk theory,[45] the bandgap energy of two
smooth FePS3 NSs, no obvious peak was detected below 10 nm. catalysts can be estimated by transforming the UV/vis diffuse
reflection absorption spectra into a Tauc plot where the X and Y
axes correspond to and
intercept of the tangent to
(
)
1/2, respectively.[46] From the
(Figure 4b), the bandgap values of
smooth and porous FePS3 nanosheets were estimated to be
1.97 and 2.04 eV, respectively in neutral environment.[47,48] After
subtracting the excitation energy (21.22 eV) (the width of He I
UPS spectra), the valence band value was calculated to be -
5.57 eV (vs EVacuum) for FePS3 porous nanosheets (-21.22 (-
16.67) 1.05). Accordingly, the valence band value of porous
FePS3 nanosheets was -5.57 eV, while its conduction band
value (Ec) was -3.53 eV (Figure 4d). The band gap was large
enough to cover both oxidation (H2
2) and reduction (H+
H2) potentials of H2O whilst generating potential differences for
hydrogen and oxygen generation of 0.47 eV and 0.34 eV,
respectively. This combination could potentially facilitate
photocatalytic water splitting using porous FePS3 nanosheets.
Figure 3. XPS spectra of the FePS3 PNSs: full XPS spectra (a); High-
resolution XPS spectra of Fe 2p (b), P 2p (c), and S 2p (d).
XPS characterization was employed here to analyze the
atomic species and bonding nature present in FePS3 PNSs
photocatalysts i.e. the ratio of exposed chalcogen atoms. From
the wide XPS spectrum, we observed P 2p, S 2p, C 1s, S 2s, O
1s, and Fe 2p peaks with binding energies of 132.4, 162.4,
226.0, 284.8, 531.7, and 710.7 eV respectively (Figure 3a). C 1s
and O 1s peaks could attribute to the conductive substrates in
the testing process. For the Fe 2p spectra (Figure 3b), we
observed two peaks with binding energies of 709.9 and 723.2
eV which corresponded to the 2p3/2 and 2p1/2 levels of Fe2+,
respectively.[40] Meanwhile, peaks with binding energies of 133.3
and 132.4 eV could be ascribed to spin-orbit splitting in P 2p1/2
and P 2p3/2, respectively (Figure 2c). Compared to the binding
energies of pure P (129.1 eV)[41] and Fe2P (130.0 eV)[42], the 2.5
eV increment in P binding energy of FePS3 (Figure 3c) could be
attributed to electron donation from P to the S-containing ligand
in FePS3 PNSs. The weak peak with a binding energy of 134.0
eV was indicative of the oxidation state of P 2p3/2 (P2O5).[43]
Similar to the P 2p core level spectra, we also observed two
intense peaks with binding energies of 161.9 and 163.3 eV.
Figure 4. UV/vis diffusive reflectance absorption spectra (a) and the estimated
bandgap potential (b) of FePS3 NSs and PNSs. Ultraviolet photoelectron
spectra (UPS) (c) and schematic depicting the specific energy levels (d) of
FePS3 PNSs.
2.2. Hydrogen generation
Firstly, the effects of sacrificial reagents, including triethylamine
(TEA), triethanolamine (TEOA), ethanol (EtOH) and methanol
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10.1002/cssc.201900789
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(MeOH), on the hydrogen production from water over FePS3
NSs and PNSs were studied under 300 W Xe lamp irradiation
(Figure S3). Obviously, the highest hydrogen production rate of
the photocatalysts was achieved in 10% TEA solution.
Specifically, the hydrogen evolution rate from smooth FePS3
nanosheets reached up to 166.2 mol h-1 g-1 (Figure 5a, TEA as
sacrificial reagents), while the porous nanosheets exhibited a
significantly higher rate of 305.6 mol h-1 g-1. The quantum
efficiency of porous FePS3 nanosheets was dependent on the
irradiation light wavelength (Figure 5b). The highest QE value of
8.3% was detected at 400 nm. The rapid decay of photocatalytic
Hydrogen generation cycle measurements are a benchmark
to evaluate photostability.[51-53] Upon illumination, hydrogen
bubbles will be generated and might accumulate on catalyst
surfaces during photocatalysis. Complete desorption of
hydrogen molecules could be achieved by reducing the system
pressure to a vacuum state after every cycling, akin to a
pressure swing adsorption setup. This would benefit hydrogen
production as the removal of hydrogen from the catalyst surface
which could drive the reaction equilibrium towards producing
more hydrogen. For contrast, continuous tests[54,55] were also
performed using FePS3 NSs and PNSs. In reality, hydrogen was
produced at a steady rate that was ~10 % lower than an ideal
situation (Ideal: 15.583 mmol vs. Reality: 13.787 mmol) over 56
h. Meanwhile, for smooth FePS3 nanosheets, the hydrogen
production rate was drastically reduced after 12 h, and then
reached almost zero during the last 28 h of testing. hydrogen
production was only observed over a period of 28 h when
smooth FePS3 nanosheets were employed (Figure 5d);
demonstrating a half photocatalytic lifetime when compared to
FePS3 PNSs. This difference in photocatalytic lifetimes could be
attributed to the surface roughness. Porous nanosheets tend to
burst larger hydrogen bubbles into smaller bubbles, and wick
activity of metal sulfides (S2- + h
S) was the main cause of
instability in these nanomaterials.[49] Here we show that this
could be overcome using di-anions (P and S) with different
electronegativities that enhanced electron delocalization of the
metal atoms to suppress photo-corrosion.[50] The photostability
of our smooth and porous FePS3 nanosheets were maintained
even after 7 cycles of batch tests over 56 h, outperforming
current state-of-the-art sulphide-based photocatalysts. The
hydrogen production efficiency of FePS3 NSs and PNSs
revealed negligible decay, demonstrating unprecedented
photostability (Figure 5c).
them away from the surface
microstructured surface of a lotus leaf.
similar to bubbles at the
[34]
Larger hydrogen
bubbles could be generated easily on the smooth surfaces of
FePS3 NSs that might consequently cover the catalytic active
site and suppress the photocatalytic activity and reduce
lifetime.[56] TEM micrographs and XRD analyses (Figures S4 and
S5, Supporting Information) of FePS3 PNSs also demonstrated
that the morphology and crystallinity of porous photocatalysts
remained intact after 56 h of continuous testing, validating the
superb photo-stability of these porous nanostructures. To further
evaluate the photocatalytic activity and stability, the same
photocatalytic system was employed in pure water without any
sacrificial reagents. Unexpectedly, the hydrogen production
rates of both smooth and porous FePS3 nanosheets were 72.9
and 118.3 mol g-1 h-1, respectively (Figure S6). The cyclic tests
over 31 h also showed good photo-stability (Figure S7).
Compared to the results of the effects of sacrificial reagents
(Figure S3), we can find MeOH and EtOH were useless for
increasing the rate of hydrogen generation in our photocatalytic
system.
Figure 6a shows the photocurrent density vs. potential
(Ag/AgCl) curves for FePS3 NSs and PNSs under dark and light
illumination. The dark current from -0.9 V to 0.3 V corresponding
to both the samples exhibit negligible. Upon illumination, the
photocurrent densities (the onset potential is around -0.9 V) of
both FePS3 photoelectrodes show improvement with increasing
applied potential. The FePS3 PNSs photoelectrode showed a
maximum photocurrent value of 0.95 mA cm-2 at 0.3 V vs.
Ag/AgCl, which is 2.3 times that of smooth sample. Transient
light responses of FePS3 NSs and PNSs photoelectrodes also
performed at 0 vs. Ag/AgCl with light on (for 50 s) and off (for 50
s) over 6 cycles (Figure S8). For porous nanosheets, a
negligible photocurrent spike value due to the slight transient
effect in power excitation was observed immediately[57] and
Figure 5. Photocatalytic hydrogen evolution rates of the FePS3 NSs and PNSs
(a) (200 mL deionized water with 10% triethylamine (TEA) as sacrificial
reagents, 300 W Xe lamp) and monochromatic light quantum efficiency of
porous FePS3 nanosheets (b). Uncontinuous (c) and continuous (d) cycling
measurements of hydrogen generation of the smooth and porous FePS3
nanosheets (Blue dotted lines = ideal hydrogen production rates).
returned to
a
steady value of ~0.6 mA cm-2 quickly,
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10.1002/cssc.201900789
ChemSusChem
demonstrating
a
stable photoelectrochemical process.
possible mechanistic explanation of the improved photocatalytic
hydrogen generation on the FePSs system with TEA as a
sacrificial reagent has been proposed as shown in Figure 6d.
Electrochemical impedance spectroscopy revealed the interface
charge transfer character of FePS3 NSs and PNSs. The arc
diameters in the EIS plot (Figure 6b) of porous FePS3
nanosheets were smaller than their smooth counterparts,
indicating a lower resistance of the interfacial charge transfer
between conductive substrates and FePS3 porous nanocatalysts.
3. Conclusions
In summary, iron phosphosulfide porous nanosheets (FePS3)
photocatalysts with remarkable photocatalytic activity and
photostability were synthesized via a facile in-situ thermal
sulfurphosphidation process. Under Xe lamp driven conditions,
porous FePS3 nanosheets exhibited enhanced photocatalytic
hydrogen production rates (305.6 mol h-1 g-1) when compared
to smooth FePS3 nanosheets (166.2 mol h-1 g-1). More
importantly, the unprecedented photo-stability of porous FePS3
nanosheets was demonstrated through a 56 h continuous
hydrogen production test. The proposed strategy for fabricating
porous di-anion semiconductor photocatalysts with high specific
surface areas might bring new opportunities in developing highly
effective and durable photocatalysts for a wide range of
sustainable energy conversion and production applications.
4. Experimental Section
4.1 Synthesis of Fe2(CO3)(OH)2 precursor
Figure 6. Photocurrent density-potential (J-V) curves vs. Ag/AgCl (a) and
electrochemical impedance spectroscopy (EIS) plots in dark (b) of FePS3 NSs
and PNSs. (c) The rate of evolution of gaseous products in the photocatalytic
reaction of 10% TEA with D2O. (d) Schematic of photocatalytic reaction
processes for the FePS3.
Uniform Fe2(CO3)(OH)2 nanosheets were synthesized by
a simple
hydrothermal process. All chemicals in this work are of analytical purity
and used without further purification. 1.35 g of iron nitrate hexahydrate
(Fe(NO3)3·9H2O, 98%, Sigma-Aldrich) was dissolved in 38 mL of distilled
water to form a clear solution by magnetic stirring, After that, 0.11 g of
urea (CO(NH2)2, AR, Shanghai Chemical Factory of China) and 0.04 g
poly(vinylpyrrolidone) (PVP, AR, Shanghai Chemical Factory of China)
were added successively. After 30 min of magnetic stirring , the mixture
was transferred to a 50 mL Teflon-lined stainless autoclave and heated
at 140 °C for 12 h. Upon cooling to room temperature naturally, the
precipitate was collected by centrifugation and washed with distilled
water and ethanol and dried in a vacuum oven at 50 °C for 12 h. The
powder was collected and dried in a vacuum oven at 60 °C for 8 h.
2.3. Degradation Mechanism of Sacrificial Reagents
As Bahnemann[58] and Jin[59] claimed, for photocatalysis
hydrogen generation system with sacrificial electron donors,
hydrogen will be formed through both the direct reductive (H2O)
as well as the indirect oxidative (sacrificial reagent) paths.
Therefore, the role of optimal sacrificial reagent (TEA) was
investigated to understand the mechanism of photocatalytic
hydrogen production over the FePS3 PNSs. Diethylamine (DEA)
and acetaldehyde are main products during the photocatalysis
process (20 h) from the results of HPLC (Figure S9) and LC-MS
(Figure S10) (74.0 and 102.1 mass are indexed to DEA and TEA,
respectively). Besides, D2O was used instead of H2O for the
photocatalytic hydrogen evolution with the FePS3 PNSs
nanocatalyst (10% TEA) to represent the yield of photocatalytic
hydrogen generation accurately as shown in Figure 6c. The
4.2 Synthesis of FePS3
Smooth FePS3 nanosheets were synthesized by a one-step sulfur-
phosphidation method with little modification.33 The obtained
Fe2(CO3)(OH)2 precursor were placed at the downstream end of a tube
furnace ( outside the heating area of the furnace) and a 1:1 mixture of
sulphur (Sigma-Aldrich, 99.5 %) and phosphorus (Sigma-Aldrich, 99.0%)
powders was placed in alumina boat at the upstream side of the tube
furnace. The furnace was first heated to 200 °C within 20 min and
maintained for 15 min under Ar carrier gas (99.999%) at 50 sccm. After
cooling to room temperature naturally, the alumina boat containing a
thiophosphate (PxSy) paste-like product was moved to the upstream edge
of the furnace, and the precursor vessel (Fe2(CO3)(OH)2) was moved to
the heating zone of the furnace. The furnace was then heated to 500 °C
for 1 h to convert these precursors into FePS3 before the furnace was
cooled down naturally. To produce FePS3 porous nanosheets, the
precursor vessel was moved into the heating zone of the furnace which
was heated to 400 °C for 2 h and then 500 °C for 1 h to complete the
rates of gaseous products including D2, H2, and HD are 39.2, 3.8,
-1
and 3.7
g-1, respectively. Intuitively, the reaction results
with D2O instead of H2O indicate that H2O may be a main
hydrogen source, similar with the previous literatures such as g-
[60]
C3N4
and CdS[61] catalysts. Compared with the rate of
hydrogen evolution from H2O (305.6 mol h-1 g-1), the low rate of
gaseous products may attribute to the difference between D+
and H+. According to the recent reports, sacrificial organic
electron donors may be a main hydrogen source on the TiO2
based catalyst system.[62,63] On the basis of the above results, a
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10.1002/cssc.201900789
ChemSusChem
transformation. Precursor Fe2(CO3)(OH)2 can be decomposed to produce
porous under 400 °C before sulfurphosphidation process.
samples were immersed in the electrolyte composed of 0.01 M Na2SO4
aqueous solution, which acts as the sacrificial hole scavenger. The
electrolyte solution was continuously purged with N2 to remove any
dissolved oxygen before test.
4.3 Materials Characterizations
Conflicts of interest
The morphologies of the samples were characterized by transmission
electron microscopy (TEM) (FEI Tecnai F20) with an acceleration voltage
of 200 kV. Scanning transmission electron microscopy (STEM) was
performed using a FEI Titan 80-200 (ChemiSTEM) electron microscope
operated at 200 kV, equipped with a high angle annular dark field
(HAADF) detector, while compositional maps were obtained with energy
dispersive spectroscopy (EDS) using four large solid-angle symmetrical
Si drift detectors. Scanning electron microscopy (SEM) was performed
on a Hitachi S-4800 scanning electron microscope. X-ray photoelectron
The authors declare no competing financial interest.
Acknowledgements
We acknowledge the National Natural Science Foundation of
China (51602161, U1732126, 51872145, 61874060), the Key
Project of National High Technology Research of China
(2011AA050526), the Ministry of Education of China (No.
IRT1148), the National Synergetic Innovation Center for
Advanced Materials (SICAM), the Natural Science Foundation of
Jiangsu Province, China (BM2012010), the Project Funded by
the Priority Academic Program Development of Jiangsu Higher
Education Institutions (PAPD, YX03001).
excitation source. The valence band energy of the samples was analyzed
on Thermo Scientific ESCALab 250Xi using Ultraviolet photoelectron
spectra (UPS). The BET surface area was measured using the nitrogen
gas adsorption-desorption method (TriStar II 3020) at 77 K. XRD
measurements were carried out on
a BRUKER D8 Advance X-
with a laser micro-Raman spectrometer (Renishaw in Via, 532 nm
excitation wavelength). UV/vis DRS were recorded on a Lambda 750
spectrophotometer equipped with an integrating sphere. Inductively
coupled plasma atomic emission spectrometry (ICP-AES) analysis was
performed on a Thermo ICAP-6300 instrument (USA). An Agilent 1260
Keywords: FePS3
porous nanosheets
photocatalysis
hydrogen evolution stability
high-performance liquid chromatograph (HPLC) equipped with
a
Phenomenex column coupled with a
References
diode array detector was used. The mobile phases for TEA solutions
were prepared by mixing water and methanol in a volume ratio of 75:25.
In addition, an Agilent 6130 series quadrupole liquid chromatography
mass spectrometry (LC-MS) system equipped with an electrospray
ionization source and an atmospheric pressure chemical ionization
source in the positive ion mode were used. Detection using Phenomenex
column (40 °C), and water/acetonitrile (95:5, v/v)
as the mobile phase was carried out. The apparent quantum efficiency
(QE) was measured under the same photocatalytic reaction condition. A
power meter (1916-R Newport) was used for the measurement of light
intensity. The QE plotted were estimated though several cut-off filters,
and were calculated on the basis of the number of the incident photons in
each wavelength region. Accordingly, each value is plotted in the middle
of two cut-off wavelengths. The QE was calculated according to eq (1):
[1]
[2]
[3]
[4]
[5]
[6]
Y. Tachibana, L. Vayssieres, J. R. Durrant, Nat. Photonics 2012, 6, 511-
518.
J. Zhang, L. Wang, X. Liu, X. Li, W. Huang, J. Mater. Chem. A 2015, 3,
535-541.
J. Mahmood, F. Li, S. Jung, M. Okyay, I. Ahmad, S. Kim, N. Park, H.
Jeong, J. Baek, Nat. Nanotechnol. 2017, 12, 441-446.
J. Tang, J. R. Durrant, D. R. Klug, J. Am. Chem. Soc. 2008, 130, 13885-
13891.
J. Cai, Y. Zhu, D. Liu, M. Meng, Z. Hu, Z. Jiang, ACS Catal. 2015, 5,
1708-1716.
G. Zhang, M. Zhang, X. Ye, X. Qiu, S. Lin, X. Wang, Adv. Mater. 2014,
26, 805-809.
[7]
[8]
B. Ma, D. Li, X. Wang, K. Lin, Chemsuschem, 2018, 11, 3871-3881.
W. Chen, Z. He, G. Huang, C. Wu, W. Wu and X. Liu, Chem. Eng. J.,
2019, 359, 244-253.
[9]
X. Cai, L. Mao, S. Yang, K. Han and J. Zhang, ACS Energy Lett., 2018,
3, 932-939.
[10] J. Ran, W. Guo, H. Wang, B. Zhu, J. Yu, S. Qiao, Adv. Mater. 2018, 30,
(1)
1800128.
[11]
W. Chen, T. Liu, T. Huang, X. Liu, X. Yang, Nanoscale 2016, 8, 3711-
4.4 Measurement of Photocatalytic Hydrogen Evolution
3719.
[12] Q. Li, B. Guo, J. Ran, B. Zhang, H. Yan, J. Gong, J. Am. Chem. Soc.
2011, 133, 10878-10884.
The photocatalytic hydrogen production experiments were carried out in
a closed gas-circulation system. A 300 W Xe lamp served as the light
source. In a typical photocatalytic experiment, 0.01 g of catalyst was
dispersed in an aqueous solution (200 mL) containing 10% sacrificial
reagents (triethylamine, triethanolamine, ethanol and methanol). Before
irradiation, the system was vacuumed for about 30 min to remove the air
inside and to ensure that the system was under the anaerobic condition.
During irradiation, continuous stirring was applied to keep the samples in
suspension. Evolved hydrogen was analyzed using a gas chromatograph
(Shimadzu GC-14C). The J-V performance of the photoanodes was
evaluated in a typical three-electrode arrangement, consisting of a FePS3
photoanodes as the working electrode, Pt as the counter electrode, and
Ag/AgCl (saturated KCl) as the reference electrode. The prepared
[13] J. Zhang, L. Qi, J. Ran, J. Yu, S. Qiao, Adv. Energy Mater. 2014, 4,
1301925.
[14]
X. Zong, G. Wu, G. Ma, F. Wen, L. Wang, C. Li, J. Am. Chem. Soc.
2008, 130, 7176-7177.
[15]
Q. Wang, J. Huang, H. Sun, Y. Ng, K. Zhang, Y. Lai, Chemsuschem
2018, 11, 1708-1721.
[16] X. Li, S. Liu, K. Fan, Z. Liu, B. Song, J. Yu, Adv. Energy Mater. 2018, 8,
1800101.
[17]
[18]
J. Meng, Q. Lin, T. Chen, X. Wei, J. Li, Z. Zhang, Nanoscale 2018, 10,
2908-2915.
J. Li, Q. Pei, R. Wang, Y. Zhou, Z. Zhang, Q. Cao, D. Wang, W. Mi, Y.
Du, ACS Nano 2018, 12, 3351-3359.
This article is protected by copyright. All rights reserved.

10.1002/cssc.201900789
ChemSusChem
[19] F. Tang, W. Cheng, H. Su, X. Zhao, Q. Liu, ACS Appl. Mater. Interfaces.
2018, 10, 6226-6234.
[41] W. S. Xia, Y. Fan, Y. S. Jiang, Y. Chen, Appl. Surf. Sci. 1996, 103, l-9.
[42] F. Luo, H. Su, W. Song, Z. Wang, Z. Yan, C. Yan, J. Mater. Chem. 2004,
14, 111-115.
[20] P. Liu, H. Sun, X. Liu, H. Sui, Y. Zhang, D. Zhou, Q. Guo, Y. Ruan, J.
Am. Ceram. Soc. 2017, 100, 3540-3549.
[43] C. C. Mayorga, Z. Sofer, D. Sedmidubsky, S. Huber, A. Y. S. Eng, M.
Pumera, ACS Appl. Mater. Interfaces 2017, 9, 12563-12573.
[44] W. Li, Z. Wu, J. Wang, A. A. Elzatahry, D. Zhao, Chem. Mater. 2014, 26,
287-298.
[21] P. Zhao, Y. Li, L. Li, S. Bu, W. Fan, J. Phys. Chem. C 2018, 122, 10737-
10748.
[22] Z. Wang, J. Peng, X. Feng, Z. Ding, Z. Li, Catal. Sci. Technol. 2017, 7,
2524-2530.
[45] Y. C. Zhang, Z. N. Du, K. W. Li, M. Zhang, D. D. Dionysiou, ACS Appl.
Mater. Interfaces 2011, 3, 1528-1537.
[23] J. Zhang, Q. Zhang, L. Wang, X. Li, W. Sci. Rep. 2016, 6, 27241.
[24] R. Musmao, Z. Sofer, D. Sedmidubsky, S. Huber and M. Pumera, ACS
Catal. 2017, 7, 8159-8170.
[46] Z. Cheng, F. Wang, T. A. Shifa, C. Jiang, Q. Liu, J. He, Small 2017, 13,
1702163.
[25]
K. Du, X. Wang, Y. Liu, P. Hu, M. I. B. Utama, C. K. Gan, Q. Xiong and
[47] X. Lv, W. Wei, Q. Sun, F. Li, B. Huang, Y. Dai, Appl. Catal. B-Environ.
2017, 217, 275-284.
C. Kloc, ACS Nano, 2016, 10, 1738-1743.
[26] Z. Wu, X. Li, W. Liu, Y. Zhong, Q. Gan, X. Li, H. Wang, ACS Catal. 2017,
7, 4026-4032.
[48] P.Zhao, Y. Ma, X. Lv, M. Li, B. Huang, Y. Dai, Nano Energy 2018, 51,
533-538.
[27] V. Nicolosi, M. Chhowalla, M. G. Kanatzidis, M. S. Strano, J. N. Coleman,
Science 2013, 340, 1226419.
[49] J. Zhang, W. Zhu, X. Liu, Dalton Trans. 2014, 43, 9296-9302.
[50] M. Caban-Acevedo, M. L. Stone, J. R. Schmidt, J. G. Thomas, Q. Ding,
H. Chang, M. Tsai, J. He, S. Jin, Nat. Mater. 2015, 14, 1245-1251.
[51] K. Yu, C. Zhang, Y. Chang, Y. Feng, Z. Yang, T. Yang, L. Lou, S. Liu,
Appl. Catal. B-Environ. 2017, 200, 514-520.
[28]
D. Mukherjee, P. M. Austeris, S. Sampath, ACS Energy Lett. 2016, 1,
367-372.
[29] X. Wang, K. Du, Y. Y. Fredrik Liu, P. Hu, J. Zhang, Q. Zhang, M. H. S.
Owen, X. Lu, C. K. Gan, P. Sengupta, C. Kloc, Q. Xiong, 2D Mater.
2016, 3, 031009.
[52] Y. Zhang, L. Wu, X. Zhao, Y. Zhao, H. Tan, X. Zhao, Y. Ma, Z. Zhao, S.
Song, Y. Wang, Y. Li, Adv. Energy Mater. 2018, 9, 1801139.
[53] F. Wang, T. Shifa, P. Yu, P. He, Y. Liu, F. Wang, Z. Wang, X. Zhan, X.
Lou, F. Xia, J. He, Adv. Funct. Mater. 2018, 28, 1802151
[54] T. Ohno, L. Bai, T. Hisatomi, K. Maeda, K. Domen, J. Am. Chem. Soc.
2012, 134, 8254-8259.
[30] F. Wang, T. A. Shifa, P. He, Z. Cheng, J. Chu, Y. Liu, Z. Wang, F. Wang,
Y. Wen, L. Liang, J. He, Nano Energy 2017, 40, 673-680.
[31] T. A. Shifa, F. Wang, Z. Cheng, P. He, Y. Liu, C. Jiang, Z. Wang, J. He,
Adv. Funct. Mater. 2018, 28, 1800548.
[32] Z. Cheng, T. A. Shifa, F. Wang, Y. Gao, P. He, K. Zhang, C. Jiang, Q.
Liu, J. He, Adv. Mater. 2018, 30, 1707433.
[55] W. Feng, L. Zhang, Y. Zhang, Y. Yang, Z. Fang, B. Wang, S. Zhang, P.
Liu, J. Mater. Chem. A 2017, 5, 10311-10320.
[33] J. Zhang, R, Cui, X. Li, X. Liu, W. Huang, J. Mater. Chem. A 2017, 5,
23536-23542.
[56] M. S. Faber, R. Dziedzic, M. A. Lukowski, N. S. Kaiser, Q. Ding, S. Jin,
J. Am. Chem. Soc. 2014, 136, 10053-10061.
[34] J. Wang, Y. Zheng, F. Nie, J. Zhai, L. Jiang, Langmuir 2009, 25, 14129-
14134.
[57] X. Yang, A. Wolcott, G. Wang, A. Sobo, R. C. Fitzmorris, F. Qian, J. Z.
Zhang, Y. Li, Nano Lett. 2009, 9, 2331-2336.
[35] B. Song, K. Li, Y. Yin, T. Wu, L. Dang, M. Caban-Acevedo, J. Han, T.
Gao, X. Wang, Z. Zhang, J. Schmidt, P. Xu, S. Jin, ACS Catal. 2017, 7,
8549-8557.
[58] J. Schneider and D. W. Bahnemann, J. Phys. Chem. Lett., 2013, 4,
3479-3483.
[59] P. V. Kamat, and Jin, S. ACS Energy Lett., 2018, 3, 622-623.
[60] X. Zhang, X. Zhang, J. Li, J. Sun, J. Bian, J. Wang, Y. Qu, R. Yan, C.
Qin and L. Jing, Appl. Catal. B-Environ., 2018, 237, 50-58.
[61] Q. Li, F. Zhao, C. Qu, Q. Shang, Z. Xu, L. Yu, J. R. McBride and T. Lian,
J. Am. Chem. Soc., 2018, 140, 11726-11734.
[36] W. Zhu, W. Gan, Z. Muhannad, C. Wang, C. Wu, H. Liu, D. Liu, K.
Zhang, Q. He, H. Jiang, X. Zheng, Z. Sun, S. Chen, L. Song, Chem.
Commun. 2018, 54, 4481-4484.
[37] G. Ouvrard, R. Brec, J. Rouxel, Mater. Res. Bull. 1985, 20, 1181-1189.
[38] M. Scagliotti, M. Jouanne, M. Balkanski, G. Ouvrard, G. Benedek, Phys.
Rev. B 1987, 35, 7097.
[62] Y. AlSalka, A. Hakki, J. Schneider and D. W. Bahnemann, Appl. Catal.
B-Environ., 2018, 238, 422-433.
[39] Y. Wang, D. Zhao, Chem. Rev. 2007, 107, 2821-2860.
[40] M. C. Biesinger, B. P. Payne, A. P. Grosvenor, L. W. M. Lau, A. R.
Gerson, R. S. C. Smart, Appl. Surf. Sci. 2011, 257, 2717-2730.
[63] S. Fujita, H. Kawamori, D. Honda, H. Yoshida and M. Arai, Appl. Catal.
B-Environ., 2016, 181, 818-824.
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FULL PAPER
Tailoring the porosity in iron
Jian Zhang, Fang Feng, Yong Pu,
Cher Hon Lau, and Wei
Huang*
phosphosulfide nanosheets to
improve stability and efficiency of
photocatalytic hydrogen evolution
Tailoring the porosity in iron
phosphosulfide nanosheets to
improve performance of
photocatalytic hydrogen evolution
This article is protected by copyright. All rights reserved.