Highly Active Sb2S3-Attached MoâWO3 Composite Film for Enhanced

Subscriber access provided by BUFFALO STATE

Article

Highly active Sb2S3 attached Mo-WO3 composite film for enhanced photoelectrocatalytic water splitting at extremely low input light energy Hao Du, Changzhu Yang, Wenhong Pu, Hao Zhao, and Jianyu Gong ACS Sustainable Chem. Eng., Just Accepted Manuscript • DOI: 10.1021/ acssuschemeng.8b06545 • Publication Date (Web): 15 Apr 2019 Downloaded from http://pubs.acs.org on April 17, 2019

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 37 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Sustainable Chemistry & Engineering

Highly active Sb2S3 attached Mo-WO3 composite film for enhanced photoelectrocatalytic water splitting at extremely low input light energy

Hao Du †, Changzhu Yang †, Wenhong Pu, Hao Zhao, and Jianyu Gong *

School of Environmental Science and Engineering, Huazhong University of Science and Technology, Luoyu Road 1037#, Wuhan, 430074, China

*Corresponding author contact information: Associate Prof. Jianyu Gong Email: [email protected]

† These authors contributed equally to this work.

1 ACS Paragon Plus Environment

ACS Sustainable Chemistry & Engineering 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Abstract We prepared platelike Mo-doped WO3 films (Mo-WO3) deposited with Sb2S3 for photoelectrocatalytic (PEC) water splitting under visible light illumination at extremely low input energy (1 mW cm-2). The 5% Mo-WO3 film exhibited optimal PEC water splitting performance. Furthermore, Sb2S3 /5% Mo-WO3 composite film achieved the highest photocurrent density of 0.42 mA cm-2, nearly 20 times as high as that of 5% Mo-WO3 film. The outstanding PEC water splitting performance was mainly attributed to synergistic effects of Mo doping and deposited Sb2S3, that is, the enhanced PEC performance was not only assigned to the broadened optical spectrum but improved electron-hole pairs separation and transfer efficiency. Density functional theory (DFT) calculation revealed that Mo dopant can modulate the intrinsic electronic structure of WO3 and introduce impurity energy levels resulting from the hybridization between M 3d and O 2p states around the Fermi level, resulting in the improved electrical conductivity. Therefore, this work offers a new sight for designing metal elements doping into WO3 associated with multifunctional electrode materials for high PEC visible light induced water splitting activity in neutral electrolyte.

Keywords: Spin coating; Sb2S3/Mo-WO3; Synergistic effect; Photoelectrochemical; Water splitting


Page 2 of 37

Page 3 of 37 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Introduction In recent decades, along with the rise of population and development of economy, the global energy demand continuously increased. It is predicted that fossil energy, such as coal, crude oil and natural gas, will be depleted in the foreseeable future, which threaten the sustainable development of human society.1 To solve current resource shortage and environmental problems confronting the modern society, it is essential to find secure, sustainable and clean energy sources instead of fossil fuels.2-3 Molecular hydrogen (H2), as one of the most appealing alternative energy sources, mainly obtained from the reforming of coal, oil and natural gas resulting in exorbitant cost and secondary environmental pollution.4-7 Therefore, seeking a green, economic and environmentally friendly strategy for hydrogen production is urgently needed. Since Fujishima and Honda8 firstly demonstrated the feasibility of decompose water using TiO2 semiconductor in 1972, photocatalytic (PC) water splitting has been extensively deemed as a promising strategy for producing H2 and O2 from solar energy.9-10 Nonetheless, low water splitting efficiency extensively limited its practical application owing to fast recombination rate of charge carriers. PEC water splitting can effectively avoid the aforementioned issues due to fast electron-hole pairs separation assisted by bias potential and the catalysts deposited on substrates.11-12 However, exploring semiconductor photocatalyst with low capital cost, long-term stability and high catalytic activity for PEC research still remained a significant challenge.13-14 3 ACS Paragon Plus Environment


Page 4 of 37

Up to now, various metal oxide semiconductor, such as TiO2,15-16 Fe2O3,17-18 WO3,19-20 ZnO 21 and BiVO4,22-23 have been widely investigated as electrode materials for PEC water splitting. Among these semiconductor materials studied, WO3, as one of the most appealing photoanode materials, has received considerable attention for solar light induced water oxidation due to moderate band gap of 2.6-2.8 eV,24 short hole diffusion length (∼150 nm),25 excellent photostability in acidic condition26 and high electron transport.27 Nevertheless, despite the above-mentioned advantages, WO3 is still suffering from inferior visible light absorption, poor solar-to-hydrogen conversion efficiency,28 short lifetime29 and slow OER kinetics..30 Therefore, to enhance the PEC activity of WO3, various strategies have been proposed including impurity doping (metal or non-metal),29,

31

morphology controlling,26,

32

surface

modification.33-34 In particularly, impurity doping is a promising approach to improve the carrier mobility and conductivity of semiconductor, further enhancing their PEC performance, due to modification of energy levels by doping35 and increased

charge

carrier density.36 Wang35 et al. demonstrated that substituting W in the lattice by isovalent Mo can narrow the band gap of WO3 confirmed by DFT calculations due to the similar ionic radius benefiting to replacement of each other . Apart from doping, combination of two semiconductors was proved to be also an excellent strategy to enhance PEC activity. For instance, CoOx/WO3 anodes could extremely enhance PEC water splitting efficiency.37 Metal chalcogenides, as an inorganic semiconductor material, has greatly promising application in the field of photocatalysis

due

to

its

suitable band

energy.38


Among

the

candidate

Page 5 of 37 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


semiconductors, Sb2S3 (stibnite) has attracted considerable attention as a highly efficient light absorbing material owing to its appropriate band gap of 1.7 eV-1.9 eV, high optical absorption coefficient of 1.8×105 cm-1 in visible light region, as well as relatively eco-friendly properties.39-40 Moreover, the synergistic effect of doping and cocatalyst deposition toward PEC water splitting had been reported.41-44 Herein, we reported highly active Sb2S3/Mo-WO3 composite film prepared by spin-coating approach, which exhibited superior PEC water splitting performance under simulated illumination (λ > 420 nm). We also characterized the synthesized films detailedly. Experimental Reagents Na2WO4·2H2O,

C2H8N2O4·H2O,

(NH4)2MoO4,

SbCl3,

CN2H4S,

N,

N-dimethyllformamide (DMF) were obtained from Sinopharm. All reagent in the experiment were of analytical grade and used directly unless otherwise specified. Preparation of WO3 and Mo-WO3 films WO3 and Mo-WO3 films were synthesized by hydrothermal process. Firstly, 10 ml of diluted HCl was added into 30 ml of 0.03 M Na2WO4·2H2O solution under strong mixing for 20 minutes. Then, 1.4 mmol C2H8N2O4·H2O was added into this above solution with the addition of 30 ml water. Finally, different amounts of (NH4)2MoO4 were added in the above resulting homogeneous solution with strong stirring. After that, the mixture and a piece of dried and cleaned FTO with conductive side facing down were transferred into a Teflon-lined stainless steel autoclave with 5 ACS Paragon Plus Environment


Page 6 of 37

volume of 100 mL and reacted at 140 °C for 3 h. Thereafter, the prepared precursor was rinsed thoroughly with pure water and ethanol, respectively. Subsequently, the obtained precursor was annealed at 500 °C for 2 h. The prepared films were expressed as WO3 and Mo-WO3 films. Preparation of Sb2S3/Mo-WO3 film First, 0.32 g SbCl3 was dissolved into 1ml DMF and stirred for at least 0.5 h. Then, 0.19 g CN2H4S was dissolved to the above resulting solution with strong stirring for about 0.5 h to form yellow solution. The Sb2S3/Mo-WO3 composite film was prepared by depositing Sb2S3 precursor solution onto Mo-WO3 film using spin-coating process at fixed rotation speed of 500 rpm for 6 s and 2000 rpm for another 30 s. The resulted specimens were calcined at 200 ℃ for 0.5 h under a nitrogen atmosphere. Characterization measurements The Sirion 200 FE-SEM (FEI, Netherlands) and JEM-2100F STEM/EDS (Energy Dispersive Spectrometer) HRTEM (JEOL, Japan) were employed to measure the micromorphology. The crystalline structure was identified by X-ray diffraction (XRD-7000, Shimadzu, Japan) under Cu Kα radiation (wavelength 0.154 nm). X-ray photoelectron spectra (XPS) measurements were carried out by a 5300 ESCA instrument (Perkin–Elmer PHI Co., USA). The UV-2600 spectrophotometer (Shimadzu, Japan) was applied to study the optical absorption property of prepared films.

A

solar

cell

quantum

efficiency

(QE)/IPCE

measurement

system

(CEL-QPCE3000) was applied to measure the incident photon-to-current conversion 6 ACS Paragon Plus Environment

Page 7 of 37 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


efficiency (IPCE). PEC water splitting measurements The photoelectrochemical tests were conducted in a quartz photoreactor with 0.1mol/L Na2SO4 as supporting electrolyte on CHI 660E electrochemical workstation with a standard three-electrode electrochemical setup. The synthesized films served as the working electrode, and Pt sheet and SCE were applied as the counter and reference electrode, respectively. A 300 W Xe lamp was adopted to supply the light source, and the distance between light source and working electrode surface was 20 cm. All potentials referred to SCE reported here were calculated with regard to reversible hydrogen electrode (RHE) values using the following Nernst equation:45 ERHE = EθSCE + ESCE + 0.0591pH

(1)

Where ESCE is the experimentally measured potential, and EθSCE = 0.242V υ s. RHE at 298 K for an SCE electrode in 0.1mol/L Na2SO4 aqueous solution. The electrochemical impedance spectra (EIS) were tested at an amplitude of 5 mV with frequency ranging from 100 mHz to 100 kHz. Mott–Schottky curves were tested at a fixed frequency of 1 KHz. Computational details All calculations were conducted with a plane-wave pseudopotential approach as implemented in the CASTEP program package within GGA.46 The catalyst was fabricated from a WO3 supercell (2 × 2 ×1) consisting of 128 atoms (32 W and 96 O atoms). Figure S1 showed that Mo-doped (Mo-WO3) was modeled by single replacement of Mo for one O atom per supercell. Geometric optimization was 7 ACS Paragon Plus Environment


performed by an ultrasoft pseudopotential. A cutoff energy at 340 eV with self-consistence-field (SCF) convergence of 1.0×10-5 eV was employed for the plane-wave expansion of the electronic wave function, and electronic property was computed by a 2 × 2 × 3 Monkhorst-Pack k-point mesh.47-48 And, the maximum tolerance of displacement and force were set as 0.001 Å and 0.03 eV/Å, respectively. Results and discussions The formation process of Mo-WO3 and Sb2S3/Mo-WO3 films was illustrated in Figure 1. Initially, the platelike film was evenly deposited on the substrate via hydrothermal method, followed by annealed. Then, the Sb2S3/Mo-WO3 was achieved by spin-coating technology and calcined again for 30 minutes under nitrogen atmosphere. Figure 2 showed the XRD patterns of different concentration of Mo-WO3 films. The diffraction peaks of WO3 film indexed to monoclinic WO3 (JCPDS No. 20-1323). Since the ionic radius of Mo6+ (0.059 nm) was close to that of W6+ (0.06 nm), it was reasonable to be deemed that the partial W6+ was substituted by Mo6+. And, the diffraction peaks at 23.08 º and 23.57 º were slightly shifted in the doped films, indicating the deformation of Mo in the crystal structure of monoclinic WO3. Similarly, the XRD pattern of Sb2S3/Mo-WO3 confirmed monoclinic WO3 and Sb2S3 (JCPDS No. 01-0538), as exhibited in Figure 3. The microstructure and morphologies of the obtained films were observed by FE-SEM. As presented in Figures 4a and 4b, the pristine WO3 film consisted of many nanoplates with rough surface. The thickness of WO3 was nearly 0.35 μm (Figure 4c). The 5% Mo-WO3 film was also made up of many nanoplates, however, the surface 8 ACS Paragon Plus Environment

Page 8 of 37

Page 9 of 37 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


morphology become smooth compared with WO3, clearly indicating that Mo doping slightly affect the surface morphology of WO3, as shown in Figure S2. Upon the Sb2S3 deposition, a deposited layer, which consisted of many aggregated nanoparticles, was observed in Figures 4d and 4e confirmed by the cross-sectional SEM images. Figure 4f showed that the thickness of two layers of films was approximately about 0.31 and 0.43 μm, respectively. The chemical composition of W, S, Sb, Mo elements in Sb2S3/5% Mo-WO3 composite film were confirmed by EDS, as shown in Figure S3. TEM images confirmed the presence of WO3 and Sb2S3, as shown in Figure 5. Obviously, an overlayer, consisting of many particles, could be observed on the Mo-WO3 surface in Figure 5a. The monoclinic WO3 (020) plane and Sb2S3 (130) plane were clearly exposed in Figure 5b, suggesting the high crystallinity of WO3 and Sb2S3. The element composition of the synthesized films was further examined by XPS. Figure 6a showed the Mo 3d, Sb 3d, S 2p, W 4f, and O 1s obviously presented in the survey spectrum of Sb2S3/5% Mo-WO3 composite film. Compared with the two peaks of W 4f spectrum in WO3 film, W 4f spectrum in Mo-WO3 film negatively shifted, further demonstrating successful doping,19 as shown in Figure 6b. The Mo 3d spectrum exhibited binding energies at 235.48 and 232.28 eV, which was the Mo6+ characteristic peaks of Mo 3d3/2 and Mo 3d5/2, respectively, and these above results further suggested the incorporation of Mo6+ into WO3 lattice (Figure 6c). Moreover, the results were in good accordance with above XRD analysis. Figure 6d showed that the Sb 3d spectrum was made up of two characteristic peaks of Sb 3d3/2 and Sb 3d5/2. 9 ACS Paragon Plus Environment


Figure 6e also showed that there were two typical peaks positioned at 162.30 eV and 161.16 eV corresponding to the S 2p1/2 and S 2p3/2, and this may be assigned to a single doublet of Sb-S bonds.49 The binding energies of S 2p and Sb 3d were all similar to the reported data, implying that Sb2S3 was successfully prepared.50 Figure 6f showed the peak at 529.88 eV in WO3 and a slightly negative shift in Mo-WO3 film in the O 1s XPS spectrum, indicating that addition of Mo increased defect or incompleteness of W−O binding.51 UV-vis absorption spectra were used to estimate the effect of Mo dopant on optical absorption properties of WO3 film (Figure 7). Compared with WO3, the doped films displayed enhanced absorption in visible light region. Apparently, incorporation of Mo extended the visible light absorption edges towards longer wavelength (Figure 7a). The 5% Mo-WO3 obtained large positive shift of visible light absorption edges from 480 nm to 520 nm. The corresponding band gap energy of 5% Mo-WO3 was 2.35 eV, much lower than that of WO3 (2.65 eV), as exhibited in Figure 7b. Furthermore, Sb2S3/5% Mo-WO3 composite film performed even better light response, extending the visible light absorption edge to 580 nm corresponding to the band gap at 1.8 eV (Figures 7c and 7d). These above results implied that Sb2S3/Mo-WO3 film might achieve outstanding PEC water splitting activity.29 Electrochemical impedance spectra with the equivalent circuit (the inset of Figure S4) were measured to estimate the interface separation and migration properties of charge carriers of the prepared electrodes. Rs stands for the series resistance, and Rct and CPE represents the charge transfer resistance and the constant 10 ACS Paragon Plus Environment

Page 10 of 37

Page 11 of 37 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


phase element at the electrode/electrolyte interface, respectively. Figure S4 showed that the 5% Mo-WO3 film performed the best charge separation property according to the calculated Rct value (12 KΩ). However, for 7% and 9% Mo-WO3 films, they exhibited even larger Rct values than that of 5% Mo-WO3 film, implying that excessive Mo doping could cause poor charge transfer at the interface of electrode. After depositing Sb2S3 on the WO3 surface, the film showed the smallest Rct value with respect to WO3 and 5% Mo-WO3 films (Figure 8a). Figure 8b showed the Nyquist plots of Sb2S3/5% Mo-WO3 composite film under different conditions. The Rct value at external potential under visible light was smaller in comparison of other conditions, implying that the electric field could effectively accelerate the separation of charge carriers.53 Mott-Schottky plots of WO3, 5% Mo-WO3 and Sb2S3/5% Mo-WO3 films were present in Figure 9. The small slope of plots indicated the high charge carrier density in the prepared films. Among the prepared films, the Sb2S3/5% Mo-WO3 displayed the smallest slope value, which was consistent with its high electronic conductivity. These results suggested that electronic conductivity of WO3 can be improved substantially by the synergistic effects of Mo doping and deposited Sb2S3, which contributed to the enhanced PEC water splitting performance. In general, the Mo-WO3 films displayed higher photocurrent density than that of pristine WO3 film, as exhibited in Figure 10a and Figure S5. Among the doped WO3 films, the 5% Mo-WO3 film exhibited the highest photocurrent density. Upon the Sb2S3 deposition, the Sb2S3/5% Mo-WO3 prepared by 1.0 mL Sb-TU displayed the highest photocurrent density with saturation photocurrent densities of 0.42 mA cm-2, 11 ACS Paragon Plus Environment


almost 90% higher than that of 5% Mo-WO3 films, implying faster charge separation and superior PEC performance, as exhibited in Figure 10b and Figure S6. Although the photocurrent density is lower than that of reported photocatalysts, the prepared Sb2S3/5% Mo-WO3 composite film still achieves effective water decomposition at low input energy. The PEC property of these films were estimated by LSV. Figure S7 exhibited the LSV curves of Mo-WO3 films. Figures. 10c and 10d showed PEC behaviors of different films as well as the Sb2S3/5% Mo-WO3 composite film under different conditions. The photocurrent densities gradually increased with the applied bias increasing, meaning the improved electron-hole pairs separation and transfer efficiency, which confirmed the enhanced PEC performance on Sb2S3/5% Mo-WO3 composite film. The IPCE was further employed to determine the light response region, which contributed to enhance PEC water activity. As shown in Figure S8, in comparison of WO3, the 5% Mo-WO3 and Sb2S3/5% Mo-WO3 films exhibited significantly enhanced PEC activity at wavelengths ranging from 300 nm to 550 nm, and the Sb2S3/5% Mo-WO3 displayed the highest PEC activity and conversion efficiency, once again demonstrating the synergistic effect of Mo dopant and deposited Sb2S3 layer. The long-term stability of as-prepared films was a vital factor for its practical applications in PEC water splitting. The photocurrent density of films was measured under continuous irradiation (λ > 420 nm) for 3 h. As shown in Figure 11, the Sb2S3 displayed remarkable photocurrent decay under visible light illumination due to its 12 ACS Paragon Plus Environment

Page 12 of 37

Page 13 of 37 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


low corrosion resistance. However, the formation of Sb2S3/5% Mo-WO3 composite film can greatly improve its photostability. The PEC water splitting process was shown in the inset of Figure 11. It was possibly because of the formation of composite film that could effectively improve the separation efficiency of electron-hole pairs, further increasing its stability. The schematic diagram of Sb2S3/5% Mo-WO3 composite film in entire PEC water splitting system was depicted in Scheme 1. The generated e and h+ mainly came from the Sb2S3/5% Mo-WO3 composite film excited by visible light. The electrons would transfer from the CB of Sb2S3 to that of WO3, and then directed rapidly to counter electrode with the help of applied voltage, thus H2O could be reduced to H2. The holes from the VB of WO3 in opposite direction migrated to that of Sb2S3 to participate in water oxidation. Thus the separation efficiency of electron-hole pairs was remarkably improved. To further investigate the effect of Mo on WO3, DFT calculations were conducted. The calculated direct band gap of WO3, 3% Mo-WO3 and 5% Mo-WO3 was 1.25 eV, 1.21 eV and 1.17 eV, respectively. (Figures 12a, 12b and 12c), which underestimates the experimental values due to failure to accurately describe the discontinuity in the exchange-related potentials.54 Figure 12d displayed the PDOS of catalysts. Moreover, the PDOS reveals that for 5% Mo-WO3, the top of the VB is dominated by the O 2p states dominate, and the bottom of the CB is dominated by the W 3d and Mo 3d states. The presence of the impurity energy levels mainly results from the hybridization between Mo 3d and O 2p states around the Fermi level, 13 ACS Paragon Plus Environment


resulting in the improved electrical conductivity.55 Thus, the improved separation efficiency of electron-hole pairs and the enhanced PEC activity of Mo-WO3 was ascribed to the reduced carrier transition energy. In order to further deeply study the mechanism of electron transfer, we calculated the electron density difference map of Mo-WO3, as displayed in Figure 13a. Due to the presence of Mo, the electron accumulation of O was much enhanced so that more photo-generated electron could be achieved. A paramagnetic impurity and doublet ground state resulted from the incorporation of Mo into WO3 lattice. A strong Mo 3d character was greatly localized on Mo atom owing to the high electron density. Obviously, Figure 13b also exhibited electron transfer from O to the coordinated Mo. Thus, higher charge depletion or accumulation around Mo can be achieved in Mo-WO3, leading to the distortion of bonds in the lattice of Mo-WO3.47 Based on the above analysis, the DFT calculations further demonstrate the primary origin of enhanced PEC water splitting activity. Conclusions In summary, vertically aligned Mo-WO3 films with different amounts of Mo dopants deposited with Sb2S3 as a photocatalyst were successfully prepared via the combination of hydrothermal method and subsequent spin-coating process. Experimental results showed Mo doped into WO3 lattice to replace partial sites of W was demonstrated by various characterizations. And, among the different amounts of Mo dopants, 5% Mo doping performed optimal PEC activity. Obviously, the Mo doping can not only enhance the optical properties but also increase electrical 14 ACS Paragon Plus Environment

Page 14 of 37

Page 15 of 37 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


conductivity, accelerating the charge transport confirmed by PEC tests. Furthermore, upon Sb2S3 depositing, Sb2S3/5% Mo-WO3 composite film achieved superior PEC water splitting performance with photocurrent density of 0.42 mA cm-2 under visible light, suggesting that depositing of Sb2S3 photocatalyst can effectively suppress the accumulation of holes at the interface of electrode and electrolyte solution and further improve photogenerated charge transfer and separation efficiency. DFT calculations reveal that Mo doping can modulate the band structure of WO3 and introduce impurity energy levels due to the effect of doped M3d. Therefore, the experimental results and DFT calculation demonstrate the primary origin of enhanced PEC water splitting activity.



Acknowledgements

This work was supported by the National Natural Science Foundation of China (Grant No. 21707038) and Hubei Provincial Natural Science Foundation of China (Grant No. 2017CFB668). The authors thank the Analytical and Testing Center of HUST for the use of XRD and SEM equipment.

Supporting Information The crystal structures of 5% Mo-WO3, SEM top view of 5% Mo-WO3, Elemental mapping of W, S, Sb and Mo and EDS spectra, Nyquist plots of WO3 and Mo-WO3, photocurrent response plots of different catalysts, Linear sweep voltammetric curves of WO3 and Mo-WO3, IPCE curves of WO3, 5% Mo-WO3 and Sb2S3/5% Mo-WO3 and Table S1.


Page 16 of 37

Page 17 of 37 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


References (1) Chen, S.; Takata, T.; Domen, K. Particulate photocatalysts for overall water splitting. Nat. Rev. Mater. 2017, 2 (10), 17050. (2) Shi, Y.; Zhang, B. Recent advances in transition metal phosphide nanomaterials: synthesis and applications in hydrogen evolution reaction. Chem. Soc. Rev. 2016, 45 (6), 1529-41, DOI: 10.1039/c5cs00434a. (3) Kment, S.; Riboni, F.; Pausova, S.; Wang, L.; Wang, L.; Han, H.; Hubicka, Z.; Krysa, J.; Schmuki, P.; Zboril, R. Photoanodes based on TiO2 and alpha-Fe2O3 for solar water splitting-superior role of 1D nanoarchitectures and of combined heterostructures.

Chem.

Soc.

Rev.

2017,

46

(12),

3716-3769,

DOI:

10.1039/c6cs00015k. (4) Babar, P.; Lokhande, A.; Shin, H. H.; Pawar, B.; Gang, M. G.; Pawar, S.; Kim, J. H. Cobalt iron hydroxide as a precious metal-free bifunctional electrocatalyst for efficient overall water splitting. Small 2018, 14 (7), DOI: 10.1002/smll.201702568. (5) Yang, L.; Lv, Y.; Cao, D. Co,N-codoped nanotube/graphene 1D/2D heterostructure for efficient oxygen reduction and hydrogen evolution reactions. J. Mater. Chem. A 2018, 6 (9), 3926-3932, DOI: 10.1039/c7ta11140a. (6) Zhang, Y.; Shao, Q.; Long, S.; Huang, X. Cobalt-molybdenum nanosheet arrays as highly efficient and stable earth-abundant electrocatalysts for overall water splitting. Nano Energy 2018, 45, 448-455, DOI: 10.1016/j.nanoen.2018.01.022. (7) Liu, G.; Zhao, Y.; Wang, K.; He, D.; Yao, R.; Li, J. Ultrasmall NiFe-phosphate nanoparticles incorporated α-Fe2O3 nanoarrays photoanode realizing high efficient 17 ACS Paragon Plus Environment


Page 18 of 37

solar water splitting. ACS Sustainable Chem. Eng. 2018, 6 (2), 2353-2361, DOI: 10.1021/acssuschemeng.7b03804. (8) Fujishima A, H. K. Electrochemical photolysis of water at a semiconductor electrode. Nature 1972, 238(5358): 37. (9) Reshak, A. H. Active photocatalytic water splitting solar-to-hydrogen energy conversion: Chalcogenide photocatalyst Ba2ZnSe3 under visible irradiation. Appl. Catal., B 2018, 221, 17-26, DOI: 10.1016/j.apcatb.2017.09.018. (10) Lee, W. P. C.; Tan, L.-L.; Sumathi, S.; Chai, S.-P. Copper-doped flower-like molybdenum disulfide/bismuth sulfide photocatalysts for enhanced solar water splitting.

Int.

J.

Hydrogen

Energy

2018,

43

(2),

748-756,

DOI:

10.1016/j.ijhydene.2017.10.169. (11) Tian, Z.; Cui, H.; Zhu, G.; Zhao, W.; Xu, J.; Shao, F.; He, J.; Huang, F. Hydrogen plasma reduced black TiO2B nanowires for enhanced photoelectrochemical water-splitting.

J.

Power

Sources

2016,

325,

697-705.,

DOI:

10.1016/j.jpowsour.2016.06.074. (12) Hu, Q.; Liu, X.; Zhu, B.; Li, G.; Fan, L.; Chai , X.; Zhang, Q.; Liu, J.; He, C. Redox route to ultrathin metal sulfides nanosheet arrays-anchored MnO2 nanoparticles as self-supported electrocatalysts for efficient water splitting. J. Power Sources 2018, 398, 159-166, DOI: 10.1016/j.jpowsour.2018.07.068. (13) Song, K.; Gao, F. M.; Yang, W. Y.; Wang, E. Y.; Wang, Z. X.; Hou, H. L. WO3 mesoporous nanobelts towards efficient photoelectrocatalysts for water splitting. Chemelectrochem 2018, 5 (2), 322-327, DOI: 10.1002/celc.201700993. 18 ACS Paragon Plus Environment

Page 19 of 37 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(14) Yao, T.; An, X.; Han, H.; Chen, J. Q.; Li, C. Photoelectrocatalytic materials for solar water splitting. Adv. Energy Mater. 2018, 8 (21), 1800210, DOI: 10.1002/aenm.201800210. (15) Gong, J.; Pu, W.; Yang, C.; Zhang, J. Novel one-step preparation of tungsten loaded TiO2 nanotube arrays with enhanced photoelectrocatalytic activity for pollutant degradation and hydrogen production. Catal. Commun. 2013, 36, 89-93, DOI: 10.1016/j.catcom.2013.03.009. (16) Freitas, R. G.; Santanna, M. A.; Pereira, E. C. Dependence of TiO2 nanotube microstructural and electronic properties on water splitting. J. Power Sources 2014, 251, 178-186, DOI: 10.1016/j.jpowsour.2013.11.067. (17) Tang, P.; Xie, H.; Ros, C.; Han, L.; Biset-Peiró, M.; He, Y.; Kramer, W.; Rodríguez, A. P.; Saucedo, E.; Galán-Mascarós, J. R.; Andreu, T.; Morante, J. R.; Arbiol, J. Enhanced photoelectrochemical water splitting of hematite multilayer nanowire photoanodes by tuning the surface state via bottom-up interfacial engineering.

Energy

Environ.

Sci.

2017,

10

(10),

2124-2136,

DOI:

10.1039/c7ee01475a. (18) Gurudayal; Jeong, D.; Jin, K.; Ahn, H.-Y.; Boix, P. P.; Abdi, F. F.; Mathews, N.; Nam, K. T.; Wong, L. H. Highly active MnO catalysts integrated onto Fe2O3 nanorods for efficient water splitting. Adv. Mater. Interfaces 2016, 3 (15), 1600176, DOI: 10.1002/admi.201600176. (19) Huang, X.; Zhao, G.; Wang, G. Sub-nano CoOx attached onto WO3 for efficient photocatalytic and photoelectrochemical water oxidation. J. Mater. Chem. A 2017, 5 19 ACS Paragon Plus Environment


Page 20 of 37

(47), 24631-24635, DOI: 10.1039/c7ta08734a. (20) Jin, B.; Jung, E.; Ma, M.; Kim, S.; Zhang, K.; Kim, J. I.; Son, Y.; Park, J. H. Solution-processed yolk–shell-shaped WO3/BiVO4 heterojunction photoelectrodes for efficient solar water splitting. J. Mater. Chem. A 2018, 6 (6), 2585-2592, DOI: 10.1039/c7ta08452h. (21) Ali, A.; Li, X.; Song, J.; Yang, S.; Zhang, W.; Zhang, Z.; Xia, R.; Zhu, L.; Xu, X. Nature-mimic ZnO nanoflowers architecture: chalcogenide quantum dots coupling with ZnO/ZnTiO3 nanoheterostructures for efficient photoelectrochemical water splitting.

J.

Phys.

Chem.

C

2017,

121

(39),

21096-21104,

DOI:

10.1021/acs.jpcc.7b04701. (22) Wang, S.; Chen, P.; Bai, Y.; Yun, J. H.; Liu, G.; Wang, L. New BiVO4 dual photoanodes with enriched oxygen vacancies for efficient solar-driven water splitting. Adv. Mater. 2018, 30 (20), e1800486, DOI: 10.1002/adma.201800486. (23) Xia, L.; Li, J.; Bai, J.; Li, L.; Zeng, Q.; Xu, Q.; Zhou, B. Preparation of a BiVO4 nanoporous photoanode based on peroxovanadate reduction and conversion for efficient photoelectrochemical performance. Nanoscale 2018, 10 (6), 2848-2855, DOI: 10.1039/c7nr07566a. (24) Cai, M.; Fan, P.; Long, J.; Han, J.; Lin, Y.; Zhang, H.; Zhong, M. Large-scale tunable 3D self-supporting WO3 micro-nano architectures as direct photoanodes for efficient photoelectrochemical water splitting. ACS Appl. Mater. Interfaces 2017, 9 (21), 17856-17864, DOI: 10.1021/acsami.7b02386. (25) Kalanur, S. S.; Hwang, Y. J.; Chae, S. Y.; Joo, O. S. Facile growth of aligned 20 ACS Paragon Plus Environment

Page 21 of 37 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


WO3 nanorods on FTO substrate for enhanced photoanodic water oxidation activity. J. Mater. Chem. A 2013, 1 (10), 3479, DOI: 10.1039/c3ta01175e. (26) Zheng, J. Y.; Song, G.; Kim, C. W.; Kang, Y. S. Fabrication of (001)-oriented monoclinic WO3 films on FTO substrates. Nanoscale 2013, 5 (12), 5279-82, DOI: 10.1039/c3nr00964e. (27) Wang, S.; Chen, H.; Gao, G.; Butburee, T.; Lyu, M.; Thaweesak, S.; Yun, J.-H.; Du, A.; Liu, G.; Wang, L. Synergistic crystal facet engineering and structural control of WO3 films exhibiting unprecedented photoelectrochemical performance. Nano Energy 2016, 24, 94-102, DOI: 10.1016/j.nanoen.2016.04.010. (28) Zheng, H.; Ou, J. Z.; Strano, M. S.; Kaner, R. B.; Mitchell, A.; Kalantar-zadeh, K. Nanostructured tungsten oxide - properties, synthesis, and applications. Adv. Funct. Mater. 2011, 21 (12), 2175-2196, DOI: 10.1002/adfm.201002477. (29) Zhang, T.; Zhu, Z.; Chen, H.; Bai, Y.; Xiao, S.; Zheng, X.; Xue, Q.; Yang, S. Iron-doping-enhanced

photoelectrochemical

water

splitting

performance

of

nanostructured WO3: a combined experimental and theoretical study. Nanoscale 2015, 7 (7), 2933-40, DOI: 10.1039/c4nr07024k. (30) Pesci, F. M.; Cowan, A. J.; Alexander, B. D.; Durrant, J. R.; Klug, D. R. Charge carrier dynamics on mesoporous WO3 during water splitting. J. Phys. Chem. Lett. 2011, 2 (15), 1900-1903, DOI: 10.1021/jz200839n. (31) Mi, Q.; Ping, Y.; Li, Y.; Cao, B.; Brunschwig, B. S.; Khalifah, P. G.; Galli, G. A.; Gray, H. B.; Lewis, N. S. Thermally stable N2-intercalated WO3 photoanodes for water

oxidation.

J.

Am.

Chem.

Soc.

2012,

134


(44),

18318-24,

DOI:


10.1021/ja3067622. (32) Zhang, J.; Zhang, P.; Wang, T.; Gong, J. Monoclinic WO3 nanomultilayers with preferentially exposed (002) facets for photoelectrochemical water splitting. Nano Energy 2015, 11, 189-195, DOI: 10.1016/j.nanoen.2014.10.021. (33) Rao, P. M.; Cai, L.; Liu, C.; Cho, I. S.; Lee, C. H.; Weisse, J. M.; Yang, P.; Zheng, X. Simultaneously efficient light absorption and charge separation in WO3/BiVO4 core/shell nanowire photoanode for photoelectrochemical water oxidation. Nano Lett. 2014, 14 (2), 1099-105, DOI: 10.1021/nl500022z. (34) de Castro, I. A.; Avansi, W.; Ribeiro, C. WO3/TiO2 heterostructures tailored by the oriented attachment mechanism: insights from their photocatalytic properties. CrystEngComm 2014, 16 (8), 1514-1524, DOI: 10.1039/c3ce41668b. (35) Wang, F.; Di Valentin, C.; Pacchioni, G. Doping of WO3 for photocatalytic water splitting: hints from density functional theory. J. Phys. Chem. C 2012, 116 (16), 8901-8909, DOI: 10.1021/jp300867j. (36) Asahi, R.; Morikawa, T.; Ohwaki, T.; Aoki, K.; Taga, Y. Visible-light photocatalysis in nitrogen-doped titanium oxides. Science 2001, 293 (5528), 269-71, DOI: 10.1126/science.1061051. (37) Huang, J.; Zhang, Y.; Ding, Y. Rationally designed/constructed CoOx/WO3 anode for efficient photoelectrochemical water oxidation. ACS Catal. 2017, 7 (3), 1841-1845, DOI: 10.1021/acscatal.7b00022. (38) Yu, Y.; Nam, G. H.; He, Q.; Wu, X. J.; Zhang, K.; Yang, Z.; Chen, J.; Ma, Q.; Zhao, M.; Liu, Z.; Ran, F. R.; Wang, X.; Li, H.; Huang, X.; Li, B.; Xiong, Q.; Zhang, 22 ACS Paragon Plus Environment

Page 22 of 37

Page 23 of 37 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Q.; Liu, Z.; Gu, L.; Du, Y.; Huang, W.; Zhang, H. High phase-purity 1T'-MoS2-and 1T'-MoSe2-layered

crystals.

Nat.

Chem.

2018,

10

(6),

638-643,

DOI:

10.1038/s41557-018-0035-6. (39) Choi, Y. C.; Seok, S. I. Efficient Sb2S3-sensitized solar cells via single-step deposition of Sb2S3 using S/Sb-ratio-controlled SbCl3-thiourea complex solution. Adv. Funct. Mater. 2015, 25 (19), 2892-2898, DOI: 10.1002/adfm.201500296. (40) Choi, Y. C.; Lee, D. U.; Noh, J. H.; Kim, E. K.; Seok, S. I. Highly improved Sb2S3 sensitized-inorganic-organic heterojunction solar cells and quantification of traps by deep-level transient spectroscopy. Adv. Funct. Mater. 2014, 24 (23), 3587-3592, DOI: 10.1002/adfm.201304238. (41) Zhang, Z.; Zhang, L.; Chen, B.; Baek, M.; Yong, K. Efficient photoconversion and charge separation of a (Mn2+-Fe2O3)/reduced graphene oxide/(Fe3+-WO3) photoelectrochemical anode via band-structure modulation. ACS Sustainable Chem. Eng. 2018, 6 (10), 13462-13472, DOI: 10.1021/acssuschemeng.8b03368 . (42) Xu, N.; Li, F.; Gao, L.; Hu, H.; Hu, Y.; Long, X.; Ma, J.; Jin, J. N, Cu-Codoped Carbon Nanosheet/Au/CuBi2O4 Photocathodes for Efficient Photoelectrochemical Water Splitting. ACS Sustainable Chem. Eng. 2018, 6 (6), 7257-7264, DOI: 10.1021/acssuschemeng.7b04133. (43) Hou, Y.; Wen, Z.; Cui, S.; Feng, X.; Chen, J. Strongly coupled ternary hybrid aerogels

of

N-deficient

porous

graphitic-C3N4

nanosheets/N-doped

graphene/NiFe-layered double hydroxide for solar-driven photoelectrochemical water oxidation. Nano Lett. 2016, 16 (4), 2268-2277, DOI: 10.1021/acs.nanolett.5b04496. 23 ACS Paragon Plus Environment


(44) Guo, J.; Yang, X.; Bai, S.; Xiang, X.; Luo, R.; He, J.; Chen, A. Effect of Mo doping and NiFe-LDH cocatalyst on PEC water oxidation efficiency. J. Colloid Interface Sci. 2019, 540, 9-19, DOI: 10.1016/j.jcis.2018.12.069. (45) Zhong, X.; He, H.; Yang, M.; Ke, G.; Zhao, Z.; Dong, F.; Wang, B.; Chen, Y.; Shi, X.; Zhou, Y. In3+-doped BiVO4 photoanodes with passivated surface states for photoelectrochemical water oxidation. J. Mater. Chem. A 2018, 6 (22), 10456-10465, DOI: 10.1039/c8ta01377b. (46) Wu, Z.; Cohen, R. E. More accurate generalized gradient approximation for solids. Phys. Rev. B 2006, 73 (23), 235116, DOI: 10.1103/PhysRevB.73.235116. (47) Gong, J.; Yang, C.; Zhang, i.; Pu, W. Origin of photocatalytic activity of W/N-codoped TiO2: H2 production and DFT calculation with GGA+ U. Appl. Catal., B 2014, 152–153 (25), 73-81, DOI: 10.1016/j.apcatb.2014.01.028. (48) Zhang, N.; Jalil, A.; Wu, D.; Chen, S.; Liu, Y.; Gao, C.; Ye, W.; Qi, Z.; Ju, H.; Wang, C.; Wu, X.; Song, L.; Zhu, J.; Xiong, Y. Refining defect states in W18O49 by Mo doping: a strategy for tuning N2 activation towards solar-driven nitrogen fixation. J. Am. Chem. Soc. 2018, 140 (30), 9434-9443, DOI: 10.1021/jacs.8b02076. (49) Wang, H.; Yuan, X.; Wang, H.; Chen, X.; Wu, Z.; Jiang, L.; Xiong, W.; Zeng, G. Facile synthesis of Sb2S3/ultrathin g-C3N4 sheets heterostructures embedded with g-C3N4 quantum dots with enhanced NIR-light photocatalytic performance. Appl. Catal., B 2016, 193, 36-46, DOI: 10.1016/j.apcatb.2016.03.075. (50) Li, J.; Yan, D.; Zhang, X.; Hou, S.; Li, D.; Lu, T.; Yao, Y.; Pan, L. In situ growth of Sb2S3 on multiwalled carbon nanotubes as high-performance anode materials for 24 ACS Paragon Plus Environment

Page 24 of 37

Page 25 of 37 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


sodium-ion

batteries.

Electrochim.

Acta

2017,

228,

436-446,

DOI:

10.1016/j.electacta.2017.01.114. (51) Wang, Y.; Liu, B.; Xiao, S.; Wang, X.; Sun, L.; Li, H.; Xie, W.; Li, Q.; Zhang, Q.; Wang, T. Low-temperature H2S detection with hierarchical Cr-doped WO3 microspheres. ACS Appl. Mater. Interfaces 2016, 8 (15), 9674-83, DOI: 10.1021/acsami.5b12857. (52) Huang, M.; Bian, J.; Xiong, W.; Huang, C.; Zhang, R. Low-dimensional Mo:BiVO4 photoanodes for enhanced photoelectrochemical activity. J. Mater. Chem. A 2018, 6 (8), 3602-3609, DOI: 10.1039/c7ta11132k. (53) Shi, W.; Li, H.; Chen, J.; Lv, X.; Shen, Y. Hierarchical WO3 nanoflakes architecture with enhanced photoelectrochemical activity. Electrochim. Acta 2017, 225, 473-481, DOI: 10.1016/j.electacta.2016.12.166. (54) Hassan, A. A.; Amine, S.; Naciri, Y.; Ahmed, C.; Cesar, J.-P.; Zakaria, A.; Mohamed, Z.; Abdeljalil, B.; Jose, A. N. Photo/electrocatalytic properties of nanocrystalline ZnO and La-doped ZnO: combined DFT fundamental semiconducting properties and experimental study. ChemistrySelect 2018, 3 (27), 7778-7791, DOI: 10.1002/slct.201801729. (55) He, B. H.; Li, Zhipeng ; Zhao, D.; Liu, H.; Zhong, Y.; Ning, J.; Zhang, Z.; Wang, Y.; Hu, Y. Fabrication of porous Cu-doped BiVO4 nanotubes as efficient oxygen-evolving photocatalysts. ACS Appl. Nano Mater. 2018, 1 (6), 2589-2599, DOI: 10.1021/acsanm.8b00281.



Figure Captions: Figure 1. Schematic representation of preparation process of Sb2S3/Mo-WO3 composite films. Figure 2. (a) XRD patterns of Mo-WO3 films (b) with a magnified small range. Figure 3. XRD patterns of WO3, 5% Mo-WO3 and Sb2S3/5% Mo-WO3 films. Figure 4. SEM images of WO3 and Sb2S3/5% Mo-WO3 composite films: (a) and (d) top view, (b) and (e) magnified top view, (c) and (f) side view. Figure 5. TEM (a) and HRTEM (b) images of Sb2S3/5% Mo-WO3 composite film. Figure 6. XPS spectra of the Sb2S3/5% Mo-WO3 composite film: (a) global spectrum and high resolution; (b) W 4f; (c) Mo 3d; (d) Sb 3d spectrum; (e) S 2p and (f) O 1S spectrum. Figure 7. UV-vis absorption spectra of (a) different Mo content doped WO3 and (c) different composite samples, and the related the plots of [αhυ]1/2 versus hυ for band-gap energies for (b) Mo-WO3 and (d) different composite samples. Figure 8. Electrochemical impedance spectra of (a) different films under visible light illumination and (b) Sb2S3/5% Mo-WO3 composite film under different conditions. Figure 9. Mott-Schottky plots of WO3, 5% Mo-WO3, Sb2S3/WO3and Sb2S3/5% Mo-WO3 films measured at a frequency of 1 kHz in 0.1 mol/L Na2SO4 solution under visible light illumination. Figure 10. (a) Steady state photocurrent density at 1.23 V υs. RHE on the basis of doping concentration; (b)Transient photocurrent density of different films at 1.23 V υ s. RHE; (c) Linear sweep voltammetric curves of different films under visible light 26 ACS Paragon Plus Environment

Page 26 of 37

Page 27 of 37 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


illumination and (d) Sb2S3/5% Mo-WO3 film in dark and under visible light illumination. Figure 11. I–t plots of Sb2S3 and Sb2S3/5% Mo-WO3 films in 0.1 M Na2SO4 (pH = 6.8) under visible light illumination. Figure 12. The calculated band structure of (a) pure WO3, (b) 3% Mo-WO3 and (c) 5% Mo-WO3, and (d) partial density of states (PDOS) of 5% Mo-WO3. Figure 13. (a) Atomic structure and (b) different electron density of 5% Mo-WO3. (showing only one plane). Scheme 1 Schematic diagram of charge separation and transfer in the Sb2S3/5% Mo-WO3 photoanode system during PEC water splitting under visible light illumination.



Figure 1.


Page 28 of 37

Page 29 of 37 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 2.

Figure 3.



Figure 4.

Figure 5.


Page 30 of 37

Page 31 of 37 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 6.



Figure 7.


Page 32 of 37

Page 33 of 37 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 8.

Figure 9.



Figure 10.

Figure 11.


Page 34 of 37

Page 35 of 37 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


b

a

c

d

Figure 12.



Figure 13.

Scheme 1


Page 36 of 37

Page 37 of 37 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


For Table of Contents Use Only

PEC water splitting into H2 and O2 was performed by the synthesized composite film under visible light illumination.


Highly Active Sb2S3-Attached MoâWO3 Composite Film for Enhanced

Recommend Documents

Highly Active Sb2S3-Attached MoâWO3 Composite Film for Enhanced