RESEARCH ARTICLE

BiOI/WO3 photoanode with enhanced photoelectrochemical water splitting activity

  • Weina SHI 1,2 ,
  • Xiaowei LV 1 ,
  • Yan SHEN , 1
Expand
  • 1. Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan 430074, China
  • 2. College of Chemistry and Chemical Engineering, Xinxiang University, Xinxiang 453003, China

Received date: 17 May 2018

Accepted date: 20 Jun 2018

Published date: 21 Dec 2018

Copyright

2018 Higher Education Press and Springer-Verlag GmbH Germany, part of Springer Nature

Abstract

This work reports on a novel BiOI/WO3 composite photoanode, which was fabricated by depositing BiOI onto a WO3 nanoflake electrode through a electrodeposition method. The photoelectrochemical (PEC) activity of the BiOI/WO3 electrode for water splitting under visible-light irradiation was evaluated. The results show that the BiOI/WO3 photoanode achieved a photocurrent density of 1.21 mA·cm−2 at 1.23 V vs. reversible hydrogen electrode (RHE), which was higher than that of the bare WO3 nanoflake electrode (0.67 mA·cm−2). The enhanced PEC acticity of BiOI/WO3 for water splitting can be attributed to the expansion of light absorption range as well as the facilitated separation of photo-generated carriers.

Cite this article

Weina SHI , Xiaowei LV , Yan SHEN . BiOI/WO3 photoanode with enhanced photoelectrochemical water splitting activity[J]. Frontiers of Optoelectronics, 2018 , 11(4) : 367 -374 . DOI: 10.1007/s12200-018-0835-8

Introduction

Photoelectrodes of semiconductor oxides have been widely investigated for photoelectrochemical (PEC) water splitting for hydrogen production [17]. Recently, great attentions have been attracted for the n-type WO3 photoanode, which has favorable valence band edge (3.0 eV versus normal hydrogen electrode), moderate hole diffusion length (~150 nm) and high electron mobility (~12 cm2·V1·s1) [8]. However, its PEC property is always limited by the relatively narrow absorption band (Eg = 2.5−2.8 eV), rapid recombination of photo-generated electron-hole pairs and tardy kinetics of holes [9]. WO3 photoanode is not suitable for efficient PEC water oxidation unless credible methods can be developed to improve its visible light absorption capacity and promote the separation of photo-generated electron-hole pairs [10].
Various strategies have been employed to solve the above mentioned problems, including doping [11], nanostructure engineering, combination of semiconductors with small band gaps and so on [1214]. For the nanostructured electrodes such as one dimensional nanorods, nanotubes and two dimensional nanoflakes, direct electrical pathways could be obtained for the photo-generated charges, and the diffusion lengths of the minority carriers could also be reduced, which lead to superior charge separation and transportation and thus excellent PEC properties [15]. For example, Amano et al. reported a 3.6 mm-thick WO3 film consisting of perpendicularly oriented crystalline flakes fabricated with hydrothermal method, which exhibited a much larger photocurrent density of ~ 2 mA·cm2 than the nanocrysalline WO3 thin film at 1.2 V vs. Ag/AgCl electrode in 0.1 mol·L1 Na2SO4 electrolyte [16]. Although the construction of nanostructured electrodes could enhance the separation of photogenerated carriers, the light absorption range of bare WO3 was limited due to its inherent nature. The design of semiconductor composite was the most widely approach to develop photoelectrocatalytic materials in the past few decades. Among the numerous semiconductor composites, the p-n heterostructured systems with a staggered (Type II) band alignment have drawn much attention due to their enhanced efficient charge separation. In the composite system, materials with small band gaps could be used to broaden its light absorption range [10,17]. BiOX (X= Cl, Br, I) is a promising candidate semiconductor, due to the strong internal electric fields from a layered structure with [Bi2O2] slabs interleaved with double halogen atom slabs along the [0 0 1] direction, leading to increase effective separation of the electron-hole pairs [18]. Among the BiOX semiconductors, BiOI has the smallest band-gap (1.8 eV) which could be motivated under most of the visible light range, with a BiOI modification can effectively enhance the PEC properties of the semiconductor photoelectrodes, such as BiOI/ZnO [19], BiOI/TiO2 [20], BiOI/BiVO4 [21]. However, there are few works focusing on the preparation and property of BiOI/WO3 electrode for PEC water splitting.
In our work, we fabricated WO3 nanoflakes by a seed-mediated hydrothermal method, which were uniformly distributed on the F doped SnO2 substrate. Subsequently, BiOI were deposited through an electrodeposition method, and crossed network structure for the BiOI/WO3 electrode was thus obtained. The as-prepared BiOI/WO3 nanocomposite electrode exhibited a significantly improved photocurrent density in Na2SO4 solution under AM 1.5G illumination. The enhanced activity was mainly ascribed to the decoration of BiOI, which expanded light absorption range and facilitated separation of photo-generated carriers for the BiOI/WO3 electrode.

Experimental section

Preparation of WO3 photoanode

The WO3 nanoflake photoanode was synthesized by hydrothermal reaction with seed-mediating according to our previously reported process [22]. The seed layer was deposited onto F doped SnO2 (FTO) substrate by spin coating followed by annealing. The H2WO4 solution for the spin-coating process was prepared by dissolving H2WO4 (2.5 g) and poly(vinyl alcohol) (1 g) into of H2O2 (30 wt. %, 34 mL). Another H2WO4 solution was prepared by adding H2WO4 (2.5 g) and H2O2 (30 wt. %, 34 mL) into deionized water (50 mL), which was heated at 95°C to form a clear solution and then diluted to a concentration of 0.05 mol·L1 for the solvothermal process. The WO3 nanoflake film was grown by adding urea (0.02 g), oxalic acid (0.02 g), HCl (6 mol·L1, 0.5 mL) and H2WO4 solution (0.05 mol·L1, 3 mL) into acetonitrile (12.5 mL). The mixture was then transferred into a Teflonlined autoclave containing the seeded FTO substrate and then maintained at 180°C for 2 h. The resulting substrate after solvothermal process was washed with deionized water and dried with nitrogen flow, and then annealing at 500°C for 2 h in air to obtain the WO3 photoanode.

Preparation of BiOI/WO3 photoanode

The BiOI/WO3 photoanode was synthesized by an electrodeposition method [23]. In a typical process, a solution containing Bi(NO3)3·5H2O (0.04 mol·L1) and KI (0.4 mol·L1) was adjusted to pH 1.7 by adding HNO3, and then 20 mL of absolute ethanol containing p-benzoquinone (0.23 mol·L1) was added into the above solution with vigorously stirring for a few minutes at room temperature. The WO3 electrode, Ag/AgCl electrode and Pt wire were served as the working electrode, reference electrode and counter electrode, respectively. Then BiOI was electrodeposited at − 0.1 V vsAg/AgCl for different deposition times (5−25 s). The optimal deposition time was 15 s, and the corresponding photocurrent density was 1.21 mA·cm2 at 1.23 V vs. reversible hydrogen electrode (RHE).

Sample characterization

X-ray diffraction (XRD) patterns of the electrodes were collected on an X-ray diffractometer (X' Pert PRO, PANalytical B.V.) using Cu Ka source radiation (1.540598 Å). Scanning electron microscopy (SEM, Nova NanoSEM 450, FEI) was used to investigate the surface morphologies of the samples. X-Ray photoelectron spectroscopy (XPS, AXIS-ULTRA DLD-600W, Shimdzu) was obtained to investigate chemical states of the samples. Raman spectra were recorded on a Raman spectrometer (LabRAM HR800) using a 532 nm laser as excitation source. UV-visible absorption spectra were obtained using a spectrophotometer (UV-3600, Shimdzu).

Photoelectrochemical measurements

PEC properties were investigated in a standard three-electrode configuration using CHI 630D electrochemical workstation (Chenhua, Shanghai, China). The as-synthesized samples acted as the working electrode, Ag/AgCl electrode and Pt wire as the reference electrode and counter electrode, respectively. 0.5 mol·L1 of Na2SO4 solution was used as the electrolyte. All potentials were converted to RHE according to the Nernst equation: ERHE = EAg/AgCl + EΘAg/AgCl+ (0.059 × pH), where EΘAg/AgCl is 0.197 V at 25°C. A gas chromatography ((Trustworthy Instrument, GC-2020N, China) with argon as a carrier gas was used for the analysis of the evolved gas. Electrochemical impedance spectroscopy (EIS) measurement was performed using an electrochemical impedance analyzer (CHI-920C) over a frequency range between 100 kHz and 0.1 Hz with an AC voltage magnitude of 5 mV amplitude at a bias potential of 1.23 V (vs. RHE).

Results and discussion

XRD measurements were carried out to determine the crystal phase of the samples. Figure 1(a) shows the XRD patterns of the WO3, BiOI and BiOI/WO3 electrodes. After subtracting the diffraction peaks of FTO substrate, all other peaks in the XRD pattern of BiOI/WO3 electrode can be indexed into tetragonal BiOI (JCPDS No. 00-010-0445) and monoclinic WO3 (JCPDS No. 00-043-1035) [24,25]. The Raman spectra of BiOI, WO3 and BiOI/WO3 were presented in Fig. 1(b). The strong peaks at 85 and 147 cm1 are assigned to Bi-I vibration of BiOI [21]. The peaks at 715 and 806 cm1 are ascribed to W-O bending (d) and W-O stretching (n) modes respectively. The peaks at 272 and 326 cm1 correspond to the bending d (O-W-O) vibrations, and the peak at 135 cm1 are assigned to the lattice vibrations of WO3 [26].
Fig.1 (a) XRD patterns of BiOI, WO3 and BiOI/WO3; (b) Raman spectra of BiOI, WO3 and BiOI/WO3

Full size|PPT slide

The SEM images of WO3 and BiOI/WO3 electrodes were depicted in Fig. 2. Figure 2(a) suggests that the pristine WO3 sample displays uniform and vertically aligned nanoflakes. The SEM images in Fig. 2(b) clearly revealed the successful deposition of BiOI sheets, which attached onto the surfaces of WO3 nanoflakes and formed crossed networks. The coating of BiOI caused an obvious color change from pale yellow to orange (digital photographs shown in the inset of Fig. 2), identifying the formation of BiOI/WO3 composite electrode.
Fig.2 SEM images of WO3 (a) and BiOI/WO3 (b) electrodes and their digital photographs (inset)

Full size|PPT slide

The chemical states of the samples are investigated by XPS. Figure 3 shows the high-resolution XPS spectra of BiOI/WO3 electrode. As shown in Fig. 3(a), the two peaks with binding energy of 38.0 and 35.9 eV correspond well with the characteristic W 4f5/2 and W 4f7/2 of W6+ in WO3, respectively [27]. Two strong peaks located at 164.4 and 159.0 eV in Fig. 3(b) are attributed to Bi 4f5/2 and Bi 4f7/2 of Bi3+ in BiOI, which are in agreement with the reported values [19]. The peaks centered at 630.4 and 618.9 eV in Fig. 3(c) are assigned to I 3d3/2 and I 3d5/2, respectively [18]. The O 1s spectrum in Fig. 3(d) could be deconvoluted into three peaks, which are related to Bi-O bonds (530.4 eV) of BiOI, W-O bonds (530.9 eV) of WO3 and O-H bonds (531.9 eV) of the surface-adsorbed water, respectively [2830].
Fig.3 High-resolution XPS spectra of the BiOI/WO3 electrode: (a) W 4f, (b) Bi 4f, (c) I 3d and (d) O 1s

Full size|PPT slide

Figure 4(a) shows the UV-visible absorption spectra of the WO3, BiOI and BiOI/WO3 electrodes. Bare WO3 nanoflakes exhibit intrinsic absorption in the wavelength of 300−450 nm. While, a rather broad absorption range of 300−630 nm was observed for the BiOI/WO3 composite, which was due to the good visible light response of BiOI. Furthermore, the indirect bandgaps of BiOI and WO3 were determined by plotting the square root of the absorption energies against the photon energies. By extrapolating the linear portions to zero (Fig. 4(b)), the band gaps were estimated to be 1.95 and 2.72 eV for BiOI and WO3, respectively, which are consistent with previous reports [31].
Fig.4 (a) UV-visible absorption spectra of BiOI, WO3 and BiOI/WO3 electrodes; (b) Tauc plots converted from the UV-visible absorption spectra for BiOI and WO3

Full size|PPT slide

Linear sweep voltammogram (LSV) measurements were conducted in 0.5 mol·L−1 Na2SO4 electrolyte to evaluate the PEC response of the samples. As shown in Fig. 5(a), both of the samples show negligible dark current densities. Upon illumination, the BiOI/WO3 composite electrode achieved a photocurrent density of 1.21 mA·cm2 at 1.23 V vs. RHE, which was 1.81 times as high as that of the pristine WO3 nanoflakes (0.67 mA·cm2). Figure 5(b) depicted the incident photon to current conversion efficiency (IPCE) spectra of the pristine WO3 and as-prepared BiOI/WO3 electrodes at 1.23 V vs. RHE. As can be seen, the WO3 electrode exhibited significant photocurrent response in the wavelength range of 350−450 nm, which was due to its intrinsic absorption. An obvious red-shift up to approximately 600 nm of the IPCE spectrum was observed for the BiOI/WO3 composite electrode, indicating the visible-light response of BiOI. Furthermore, the IPCE values for the BiOI/WO3 composite electrode were higher than those of bare WO3. In particular, the IPCE values at 405 nm for the WO3 and BiOI/WO3 electrodes reached 7.3% and 22.2%, respectively. These results indicated that the modification of BiOI improved the PEC activity of WO3.
Fig.5 (a) LSV scans of the WO3 and BiOI/WO3 electrodes in 0.5 mol·L−1 Na2SO4 electrolyte; (b) IPCE plots of the WO3 and BiOI/WO3 electrodes at 1.23 V vs. RHE in 0.5 mol·L−1 Na2SO4 electrolyte

Full size|PPT slide

Figure 6(a) shows the photocurrent densities of the obtained electrodes measured at 1.23 V vs. RHE in 0.5 mol·L−1 Na2SO4 electrolyte. The photocurrent of the bare WO3 electrode attenuated quickly at the initial time, and lost 53% of the pristine value within 2000 s. However, the BiOI/WO3 electrode exhibited a smaller attenuation of 28% as compared with that of the bare WO3. Furthermore, the gaseous products of the WO3 and BiOI/WO3 electrodes were measured as a function of time at 1.23 V vs. RHE in 0.5 mol·L−1 Na2SO4 electrolyte. As can be seen in Fig. 6(b), the amounts of H2 and O2 were close to the theoretical amounts determined by integrating the measured photocurrent over time. What’s more, the proportion of evolved H2 and O2 was 2:1, indicating that the observed photocurrent is real water splitting photocurrent, rather than due to photodegradation.
Fig.6 Photocurrent density-time curves (a) and amounts of the theoretical and actual evolved gas (b) for the WO3 and BiOI/WO3 electrodes in 0.5 mol·L−1 Na2SO4 electrolyte

Full size|PPT slide

Electrochemical impedance spectroscopy (EIS) measurements were implemented to study the interface charge transport properties of the electrodes. The charge-transfer resistance at the electrode-electrolyte interface can be reflected from the semicircle in the Nyquist plots [32]. As shown in Fig. 7(a), the BiOI/WO3 electrode exhibited a smaller semicircle as compared with that of WO3, and it indicated that the introduction of BiOI led to an efficient separation of the electron-hole pairs for the composite electrode, in accordance with its improved PEC activity. Furthermore, the band energies of BiOI and WO3 were also investigated. The conduction band (CB) and valence band (VB) edge at the point of zero charge for a semiconductor can be determined from the empirical equation [21]:
EVB=X Ee+0.5Eg,
ECB=E VB Eg ,
where EVB is the valence band edge potential, and Ee is the energy of free electrons on the hydrogen scale (~4.5 eV). X and Eg are the electronegativity and band-gap energy of the semiconductor, respectively. The X values of BiOI and WO3 are 5.94 and 6.59 eV. As shown in Fig. 7(b), pristine BiOI and WO3 owned their respective band energies before contact, which were obtained from the above UV-visible absorption spectra. When these two semiconductors are in contact, the photo-generated electrons and holes will be generated both in BiOI and WO3 as the solar light illuminate on the BiOI/WO3. The holes in WO3 diffuse to BiOI, and caused efficient separation for the photo-generated electrons and holes. The recombination process is thus remarkably suppressed, leading to improved PEC water splitting activity.
Fig.7 (a) EIS Nyquist plots of WO3 and BiOI/WO3 electrodes measured at an applied bias of 1.23 V vs. RHE under AM 1.5G illumination; (b) schematic diagrams of the band energy of BiOI and WO3 before and after contact

Full size|PPT slide

Conclusion

In summary, we have successfully fabricated a WO3 nanoflake electrode by a seed-mediated solvothermal method, followed by loading with BiOI through electrodepositing. The novel BiOI/WO3 nanocomposite electrode achieved an enhanced PEC activity for water splitting, which may be attributed to the expansion of light absorption range as well as the facilitated separation of photo-generated carriers. These findings prove that the BiOI/WO3 photoanode is a promising candidate for PEC water oxidation.

Acknowledgements

This work was financially supported by the National Natural Science Foundation of China (NSFC) Major International (Regional) Joint Research Project NSFC-SNSF (Grant No. 51661135023), NSFC (Grant No. 21673091), the National Basic Research Program (973 Program) of China (No. 2014CB643506), the Fundamental Research Funds for the Central Universities (HUST: 2016YXMS031), the Director Fund of the WNLO, the Open Funds of the State Key Laboratory of Electroanalytical Chemistry (No. SKLEAC201607), Key Scientific and Technological Project of Henan Province (No. 182102311084). The authors thank the Analytical and Testing Center of HUST and the Center for Nanoscale Characterization & Devices (CNCD), WNLO-HUST for the measurements.
1
Kim H, Monllor-Satoca D, Kim W, Choi W. N-doped TiO2 nanotubes coated with a thin TaOxNy layer for photoelectrochemical water splitting: dual bulk and surface modification of photoanodes. Energy & Environmental Science, 2015, 8(1): 247–257

DOI

2
Fan X, Wang T, Gao B, Gong H, Xue H, Guo H, Song L, Xia W, Huang X, He J. Preparation of the TiO2/graphic carbon nitride core-shell array as photoanode for efficient photoelectrochemical water splitting. Langmuir, 2016, 32(50): 13322–13332

DOI PMID

3
Ding D, Dong B, Liang J, Zhou H, Pang Y, Ding S. Solvothermal-etching process induced Ti-doped Fe2O3 thin film with low turn-on voltage for water splitting. ACS Applied Materials & Interfaces, 2016, 8(37): 24573–24578

DOI PMID

4
Feng X, Chen Y, Qin Z, Wang M, Guo L. Facile fabrication of sandwich structured WO3 nanoplate arrays for efficient photoelectrochemical water splitting. ACS Applied Materials & Interfaces, 2016, 8(28): 18089–18096

DOI PMID

5
Yan L, Zhao W, Liu Z. 1D ZnO/BiVO4 heterojunction photoanodes for efficient photoelectrochemical water splitting. Dalton Transactions (Cambridge, England), 2016, 45(28): 11346–11352

DOI PMID

6
Fan X, Wang T, Guo Y, Gong H, Xue H, Guo H, Gao B, He J. Synthesis of ordered mesoporous TiO2-Carbon-CNTs nanocomposite and its efficient photoelectrocatalytic methanol oxidation performance. Microporous and Mesoporous Materials, 2017, 240: 1–8

DOI

7
Xue H, Wang T, Gong H, Guo H, Fan X, Gao B, Feng Y, Meng X, Huang X, He J. Constructing ordered three-dimensional channels of TiO2 for enhanced visible-light photo-catalytic performance of CO2 conversion induced by Au nanoparticles. Chemistry, an Asian Journal, 2018, 13(5): 577–583

DOI PMID

8
Berak J M, Sienko M J. Effect of oxygen-deficiency on electrical transport properties of tungsten trioxide crystals. Journal of Solid State Chemistry, 1970, 2(1): 109–133

DOI

9
Mi Q, Zhanaidarova A, Brunschwig B S, Gray H B, Lewis N S. A quantitative assessment of the competition between water and anion oxidation at WO3 photoanodes in acidic aqueous electrolytes. Energy & Environmental Science, 2012, 5(2): 5694–5700

DOI

10
Li Y, Zhang L, LiuR, Cao Z, Sun X, Liu X, Luo J. WO3@a-Fe2O3 heterojunction arrays with improved photoelectrochemical behavior for neutral pH water splitting. ChemCatChem, 2016, 8(17): 2765–2770

DOI

11
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): 2933–2940

DOI PMID

12
Su J, Guo L, Bao N, Grimes C A. Nanostructured WO3/BiVO4 heterojunction films for efficient photoelectrochemical water splitting. Nano Letters, 2011, 11(5): 1928–1933

DOI PMID

13
Boudoire F, Toth R, Heier J, Braun A, Constable E C. Photonic light trapping in self-organized all-oxide microspheroids impacts photoelectrochemical water splitting. Energy & Environmental Science, 2014, 7(8): 2680–2688

DOI

14
Solarska R, Królikowska A, Augustyński J. Silver nanoparticle induced photocurrent enhancement at WO3 photoanodes. Angewandte Chemie International Edition, 2010, 49(43): 7980–7983

DOI PMID

15
Su J, Feng X, Sloppy J D, Guo L, Grimes C A. Vertically aligned WO3 nanowire arrays grown directly on transparent conducting oxide coated glass: synthesis and photoelectrochemical properties. Nano Letters, 2011, 11(1): 203–208

DOI PMID

16
Amano F, Li D, Ohtani B. Fabrication and photoelectrochemical property of tungsten(vi) oxide films with a flake-wall structure. Chemical Communications (Cambridge, England), 2010, 46(16): 2769–2771

DOI PMID

17
Mali M G, Yoon H, Kim M, Swihart M T, Al-Deyab S S, Yoon S S. Electrosprayed heterojunction WO3/BiVO4 films with nanotextured pillar structure for enhanced photoelectrochemical water splitting. Applied Physics Letters, 2015, 106(15): 151603

DOI

18
Ye L, Liu X, Zhao Q, Xie H, Zan L. Dramatic visible light photocatalytic activity of MnOx–BiOI heterogeneous photocatalysts and the selectivity of the cocatalyst. Journal of Materials Chemistry A, Materials for Energy and Sustainability, 2013, 1(31): 8978–8983

DOI

19
Kuang P Y, Ran J R, Liu Z Q, Wang H J, Li N, Su Y Z, Jin Y G, Qiao S Z. Enhanced photoelectrocatalytic activity of BiOI nanoplate-zinc oxide nanorod p-n heterojunction. Chemistry (Weinheim an der Bergstrasse, Germany), 2015, 21(43): 15360–15368

DOI PMID

20
Park H, Bak A, Ahn Y Y, Choi J, Hoffmannn M R. Photoelectrochemical performance of multi-layered BiOx-TiO2/Ti electrodes for degradation of phenol and production of molecular hydrogen in water. Journal of Hazardous Materials, 2012, 211–212: 47–54

DOI PMID

21
Ye K H, Chai Z, Gu J, Yu X, Zhao C, Zhang Y, Mai W. BiOI–BiVO4 photoanodes with significantly improved solar water splitting capability: p–n junction to expand solar adsorption range and facilitate charge carrier dynamics. Nano Energy, 2015, 18: 222–231

DOI

22
Shi W, Zhang X, Brillet J, Huang D, Li M, Wang M, Shen Y. Significant enhancement of the photoelectrochemical activity of WO3 nanoflakes by carbon quantum dots decoration. Carbon, 2016, 105: 387–393

DOI

23
Kim T W, Choi K S. Nanoporous BiVO4 photoanodes with dual-layer oxygen evolution catalysts for solar water splitting. Science, 2014, 343(6174): 990–994

DOI PMID

24
Wang J C, Yao H C, Fan Z Y, Zhang L, Wang J S, Zang S Q, Li Z J. Indirect Z-scheme BiOI/g-C3N4 photocatalysts with enhanced photoreduction CO2 activity under visible light irradiation. ACS Applied Materials & Interfaces, 2016, 8(6): 3765–3775

DOI PMID

25
Li W, Da P, Zhang Y, Wang Y, Lin X, Gong X, Zheng G. WO3 nanoflakes for enhanced photoelectrochemical conversion. ACS Nano, 2014, 8(11): 11770–11777

DOI PMID

26
Nonaka K, Takase A, Miyakawa K. Raman spectra of sol-gel-derived tungsten oxides. Journal of Materials Science Letters, 1993, 12(5): 274–277

DOI

27
Cui X, Zhang H, Dong X, Chen H, Zhang L, Guo L, Shi J. Electrochemical catalytic activity for the hydrogen oxidation of mesoporous WO3 and WO3/C composites. Journal of Materials Chemistry, 2008, 18(30): 3575–3580

DOI

28
Sun Y, Murphy C J, Reyes-Gil K R, Reyes-Garcia E A, Thornton J M, Morris N A, Raftery D. Photoelectrochemical and structural characterization of carbon-doped WO3 films prepared via spray pyrolysis. International Journal of Hydrogen Energy, 2009, 34(20): 8476–8484

DOI

29
Chang C, Zhu L, Wang S, Chu X, Yue L. Novel mesoporous graphite carbon nitride/BiOI heterojunction for enhancing photocatalytic performance under visible-light irradiation. ACS Applied Materials & Interfaces, 2014, 6(7): 5083–5093

DOI PMID

30
Zhang Y, Pei Q, Liang J, Feng T, Zhou X, Mao H, Zhang W, Hisaeda Y, Song X M. Mesoporous TiO2-based photoanode sensitized by BiOI and investigation of its photovoltaic behavior. Langmuir, 2015, 31(37): 10279–10284

DOI PMID

31
Feng Y, Liu C, Che H, Chen J, Huang K, Huang C, Shi W. The highly improved visible light photocatalytic activity of BiOI through fabricating a novel p–n heterojunction BiOI/WO3 nanocomposite. CrystEngComm, 2016, 18(10): 1790–1799

DOI

32
Hou Y, Zuo F, Dagg A P, Liu J, Feng P. Branched WO3 nanosheet array with layered C3N4 heterojunctions and CoOx nanoparticles as a flexible photoanode for efficient photoelectrochemical water oxidation. Advanced Materials, 2014, 26(29): 5043–5049

DOI PMID

Outlines

/