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(a) LSV of SnO2/WO3/BiVO4 under front (F) and back (B) illumination; (b) Photocurrent density under back and front illumination for SnO2/BiVO4 in comparison with SnO2/WO3/BiVO4; (c) LSV of SnO2/WO3 photoanode measured using a three-electrode configuration set up in aqueous phosphate buffer (pH 7.0) with 0.5 M Na2SO3.
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The performance of a BiVO4 photoanode is limited by poor charge transport, especially under front side illumination. Heterojunction of different metal oxides with staggered band configuration is a promising route, as it facilitates charge separation/transport and thereby improves photoactivity. We report a ternary planar heterojunction photoanode w...
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... properties of triple planar heterojunction were evaluated in three electrode configurations, using aqueous Na2SO3 with buffer solution as electrolyte (pH 7). Figure 2a presents LSV diagrams of SnO2/WO3/BiVO4 photoanode under one sun illumination. The photocurrent obtained from front and back illumination behavior was compared for different thicknesses of SnO2. ...
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... is interesting to note that the behavior of the front and back illumination is unaffected by increasing the thickness of WO 3 . Figure 2b presents the LSV of SnO 2 50 nm/BiVO 4 under directional illumination. SnO 2 /BiVO 4 photoanode shows ~1.2 mA/cm 2 at 1.23 V during backside illumination, while it shows a photocurrent density of ~0.5 mA/cm 2 under front side illumination . ...
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... 2 /BiVO 4 photoanode shows ~1.2 mA/cm 2 at 1.23 V during backside illumination, while it shows a photocurrent density of ~0.5 mA/cm 2 under front side illumination . Photoelectrochemical properties of heterojunction SnO 2 50 nm/WO 3 50 nm are shown in Figure 2c. ...
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... is interesting to note that the behavior of the front and back illumination is unaffected by increasing the thickness of WO3. Figure 2b presents the LSV of SnO2 50 nm/BiVO4 under directional illumination. SnO2/BiVO4 photoanode shows ~1.2 mA/cm 2 at 1.23 V during backside illumination, while it shows a photocurrent density of ~0.5 mA/cm 2 under front side illumination. ...
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... photoanode shows ~1.2 mA/cm 2 at 1.23 V during backside illumination, while it shows a photocurrent density of ~0.5 mA/cm 2 under front side illumination. Photoelectrochemical properties of heterojunction SnO2 50 nm/WO3 50 nm are shown in Figure 2c. LSV of SnO 2 /WO 3 /BiVO 4 photoanode has been carried out in the absence of a hole scavenger, which is shown in Supplementary Material Figure S1a. ...
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... SnO2 layer enhances the charge transfer properties of BiVO4 by suppressing the possible recombination that can occur at the interface of SnO2/BiVO4. When the WO3 layer is introduced between SnO2/BiVO4, the charge separation can be further enhanced, as seen from Figure 2a, where the photocurrent increased after the insertion of WO3 layer. It is evident from the published results that the heterojunction of nanostructured WO3/BiVO4 performs better than either of the individual materials due to the formation of type II heterojunction [35,36]. ...
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... SnO 2 layer enhances the charge transfer properties of BiVO 4 by suppressing the possible recombination that can occur at the interface of SnO 2 /BiVO 4 . When the WO 3 layer is introduced between SnO 2 /BiVO 4 , the charge separation can be further enhanced, as seen from Figure 2a, where the photocurrent increased after the insertion of WO 3 layer. It is evident from the published results that the heterojunction of nanostructured WO 3 /BiVO 4 performs better than either of the individual materials due to the formation of type II heterojunction [35,36]. ...
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... This was due to the proper staggered type-II band alignment, which promotes the charge transfer and separation at the interface. [42][43][44] The tted values obtained from the equivalent circuit are shown in Table S2 (ESI †). ...
n/n/n triple heterojunction photoanodes made up of Zr:W-BiVO4, Fe2O3, and ZnFe2O4 metal oxides are fabricated through a simplistic spray pyrolysis method. Use of Zr and W as dopants in BiVO4 plays an important role as Zr increases the carrier density and W reduces the charge recombination. Further, Fe2O3 and ZnFe2O4 serve as a protective layer for Zr:W-BiVO4, which augmented the photoelectrochemical performance and achieved a 1.90% conversion efficiency in the triple heterojunction. XRD measurements display the crystalline nature and reduction in particle size due to strain in the sample, UV-vis absorbance shows an extended absorption towards the visible region and the FE-SEM imaging confirms the successful deposition of ZnFe2O4 over BiVO4/Fe2O3. By analyzing the band edge position, it was observed that on formation, the triple heterojunction not only suppresses the charge carrier recombination but also utilizes the band edge offset for the water splitting reaction using solar energy.
... However, TiO 2 can only absorb the ultraviolet (UV) light because of its wide band gap of 3.2 eV, where UV light occupies only 5% of total solar spectrum [17]. Hence, the semiconductor materials with the band gap energy smaller than 3.0 eV that can absorb visible light, such as tungsten oxide (WO 3 ), bismuth vanadate (BiVO 4 ), and hematite (α-Fe 2 O 3 ), also have been employed for PEC water splitting [18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34]. ...
As the interest in sustainable energy production increases, water splitting through semiconductor materials to convert solar energy directly to hydrogen energy has been extensively reported to date. Recently, the III–VI group chalcogenide semiconductors have received great attention for narrow-gap photoelectrochemical (PEC) water splitting electrodes. Among the metal sulfides, beta indium sulfide (β-In2S3) shows remarkable properties for photoelectrodes such as high photoelectric sensitivity, high photoconductivity, large photoelectric conversion yield, low toxicity, high absorption coefficient, efficient charge separation, moderate charge transport, appropriate band position, and narrow band gap. Most of its unique properties come from the defective spinel crystal structure. Despite the superior advantages, there is a serious problem of photocorrosion induced by accumulated holes on the surface of the electrodes during the photocatalytic reaction under illumination which reduces the PEC properties. Herein, we review overall physicochemical and optoelectronic properties of β-In2S3, regardless of pros and cons, followed by the discussion of assorted strategies to further improve the PEC activities.
... To improve the photoelectrochemical performance of BiVO 4 , various metal oxides have been used to fabricate the heterojunction, including BiVO 4 /WO 3 , SnO 2 /BiVO 4 , and BiVO 4 /CuWO 4 . 10,19,27,28 Enhanced performance and stability were observed when the surface of the BiVO 4 was modified with cobalt-and nickel-based oxygen-evolving catalysts. 29,30 Deposition of oxygen-evolving catalysts such as Co 2 O 3 , NiO, and Ni/FeOOH has been investigated, and the increase in photocurrent density is due to enhanced surface reaction kinetics and charge separation. ...
BiVO4 has emerged as a promising photoanode for water oxidation. Technical barriers such as charge recombination and photocorrosion prevent its practical application. In the present work, a NiCo2O4 nanofiber cocatalyst with dual metal active sites was coupled with BiVO4 to overcome the limitations of surface recombination and sluggish water oxidation kinetics. This unique nanofiber morphology was synthesized by a facile hydrothermal technique. Photocorrosion of BiVO4 during water oxidation was addressed by conformal coating of TiO2 on BiVO4 using a simple spin-coating method. BiVO4/TiO2/NiCo2O4 exhibits a photocurrent density of 2.47 mA/cm2 at 1.23 V vs. RHE without a hole scavenger, which is 12-fold higher than that of pristine BiVO4. NiCo2O4 nanofiber decoration significantly enhances the photocurrent density of BiVO4. While conformally deposited TiO2 serves as a protection layer, the NiCo2O4 nanofibers suppress the charge recombination by forming a p-n junction, which improves the water oxidation kinetics, leading to a cathodic shift in the onset potential. This strategy can assist in the development of an effective cocatalyst with a protection layer for sustainable photoelectrochemical applications.
... Semiconductors with staggered band alignments can be coupled to fabricate the heterojunction, which can improve the solar water oxidation of the photoelectrode due to the increased charge carrier separation [7][8][9][10][11]. Nano structural modification with high surface area is beneficial to further improve the photocurrent density of the heterojunctions [12,13]. ...
Photoelectrochemical water splitting is considered as a long-term solution for the ever-increasing energy demands. Various strategies have been employed to improve the traditional TiO2 photoanode. In this study, TiO2 nanorods were decorated by graphitic carbon nitride (C3N4) derived from different precursors such as thiourea, melamine, and a mixture of thiourea and melamine. Photoelectrochemical activity of TiO2/C3N4 photoanode can be modified by tuning the number of precursors used to synthesize C3N4. C3N4 derived from the mixture of melamine and thiourea in TiO2/C3N4 photoanode showed photocurrent density as high as 2.74 mA/cm2 at 1.23 V vs. RHE. C3N4 synthesized by thiourea showed particle-like morphology, while melamine and melamine with thiourea derived C3N4 yielded two dimensional (2D) nanosheets. Nanosheet-like C3N4 showed higher photoelectrochemical performance than that of particle-like nanostructures as specific surface area, and the redox ability of nanosheets are believed to be superior to particle-like nanostructures. TiO2/C3N4 displayed excellent photostability up to 20 h under continuous illumination. Thiourea plays an important role in enhancing the photoelectrochemical performance of TiO2/C3N4. This study emphasizes the fact that the improved photoelectrochemical performance can be achieved by varying the precursors of C3N4 in TiO2/C3N4 heterojunction. This is the first report to show the influence of C3N4 precursors on photoelectrochemical performance in TiO2/C3N4 systems. This would pave the way to explore different precursors influence on C3N4 with respect to the photoelectrochemical response of TiO2/C3N4 heterojunction photoanode.
Films of heterostructure BiVO4/WO3, composite BiVO4 with WO3 and pure BiVO4 were obtained by electrochemical deposition. Analysis of photoelectrochemical characteristics of such films showed that observed increase in photocurrent quantum yield and decrease in overvoltage of oxygen evolution on the photoanode in row from pure BiVO4 films, than in heterostructure BiVO4/WO3, after that—composite BiVO4–WO3. The reason of such positive effect of reducing the energy losses associated with the surface recombination of electrons and holes and reduction of losses at the stage of interfacial charge transfer in the BiVO4–WO3 composite compared with the heterostructure BiVO4/WO3 and pure BiVO4.
Dual functional heterojunctions of tungsten oxide and bismuth vanadate (WO3/BiVO4) photoanodes are developed and their applications in photoelectrochemical (PEC) water splitting and mineralization of glycerol are demonstrated. The thin-film WO3/BiVO4 photoelectrode was fabricated by a facile hydrothermal method. The morphology, chemical composition, crystalline structure, chemical state, and optical absorption properties of the WO3/BiVO4 photoelectrodes were characterized systematically. The WO3/BiVO4 photoelectrode exhibits a good distribution of elements and a well-crystalline monoclinic WO3 and monoclinic scheelite BiVO4. The light-absorption spectrum of the WO3/BiVO4 photoelectrodes reveals a broad absorption band in the visible light region with a maximum absorption of around 520 nm. The dual functional WO3/BiVO4 photoelectrodes achieved a high photocurrent density of 6.85 mA cm-2, which is 2.8 times higher than that of the pristine WO3 photoelectrode in the presence of a mixture of 0.5 M Na2SO4 and 0.5 M glycerol electrolyte under AM 1.5 G (100 mW cm-2) illumination. The superior PEC performance of the WO3/BiVO4 photoelectrode was attributed to the synergistic effects of the superior crystal structure, light absorption, and efficient charge separation. Simultaneously, glycerol plays an essential role in increasing the efficiency of hydrogen production by suppressing charge recombination in the water redox reaction. Moreover, the WO3/BiVO4 photoelectrode shows the total organic carbon (TOC) removal efficiency of glycerol at about 82% at 120 min. Notably, the WO3/BiVO4 photoelectrode can be a promising photoelectrode for simultaneous hydrogen production and mineralization of glycerol with a simple, economical, and environmentally friendly approach.
Photoelectrochemical carbon-dioxide reduction (PEC CO2R) is a potentially attractive means for producing chemicals and fuels using sunlight, water, and carbon dioxide; however, this technology is in its infancy. To date,...
The photoelectrochemical water splitting process has a lucid and efficacious impact, which emulates the natural photosynthesis process by converting solar energy into chemical energy. The construction of a PEC system can convert H2O to H2 or CO2 to C-based fuels. To achieve artificial photosynthesis, rate-determining kinetics of the OER is regarded as a highly efficient photo-anode. BiVO4 grabbed strong attention as a photoanode in the communal of PEC. Owing to a moderate bandgap and the Earth-abundant nature of the constituents, it is considered an inexpensive n-type semiconductor for PEC H2O splitting. This chapter discussed the recent progress of BiVO4-based photoanodes fabrication, including control in the surface, effects of dopant, different synthesis techniques, co-catalyst, etc. Typical unbiased tandem devices of a photoanode system in the presence of BiVO4 are also reflected. The report also demonstrated the photocatalysis principles regarding the degradation of organic pollutants.
