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We report the synthesis of tungsten sulfide (WS2) films using RF‐magnetron sputtering at different RF powers. X‐ray diffraction (XRD) data confirm the hexagonal crystal structure of WS2 with an average crystallite size of ∼44.54 Å. With increased RF power, the preferred orientation of WS2 crystallites shifts from (002) to (100). Linear sweep voltammetry (LSV) was used to assess the Photoelectrochemical (PEC) activity of WS2 films. The film deposited at 150 W demonstrated the highest photocurrent density of 5.44 mA/cm2. The 150 W film also showed a lower Tafel slope of ∼0.374 V/decade, indicating superior PEC activity. Mott Schottky's (MS) analysis revealed a notable shift in the flat band potential towards the negative side, suggesting a shifting of the Fermi level towards the conduction band. WS2 film grown at 150 W demonstrated a majority charge carrier density of 6.2×1021 cm−3 and a depletion layer width of 1.54 nm. The observed low charge transfer resistance of 155 Ω contributed to the enhanced PEC activity with a relaxation time constant of 37 ms. These properties suggest that WS2 can be suitable for PEC water splitting. [ABSTRACT FROM AUTHOR]

Developing efficient semiconductor photoanodes demonstrating strong light absorption, efficient separation of photogenerated charge carriers, and reduced charge carrier recombination rate can benefit PEC water splitting. Integrating a wide band gap semiconductor with narrow bandgap material with suitable band alignment can enhance PEC performance. Herein, we have fabricated novel MoO3/γ-In2Se3 heterostructure photoanodes using RF magnetron sputtering. The films structural, optical, morphological, and elemental composition were investigated in detail using low-angle XRD, Raman spectroscopy, XPS analysis, EDAX, and FESEM. The XRD, Raman, XPS, and EDAX results strongly confirmed the presence of desired phases of MoO3 and γ-In2Se3 layers in heterostructure without forming any impurity or alloy. FESEM micrographs revealed a uniform, dense grain structure. Optical analysis of MoO3/γ-In2Se3 done by UV–Visible spectroscopy shows increased absorption compared to pristine-MoO3. Conduction and valence band-edge potential values indicate that MoO3/γ-In2Se3 films are suitable for PEC hydrogen production. The PEC performance of these heterostructure photoanodes was evaluated by performing LSV, Chronoamperometry, EIS, and Mott–Schottky analysis. LSV results of MoO3/γ-In2Se3 showed a 10-fold increase in photocurrent density and attained higher photoconversion efficiency (0.5%) compared to pristine-MoO3 photoanode. EIS analysis revealed that MoO3/γ-In2Se3 photoanodes had small charge transfer resistance. Investigation of Mott Schottky results shows carrier density increases from 2.8 × 1019 cm−3 to 2.1 × 1020 cm−3 after incorporating γ-In2Se3 over MoO3. An increase in time-dependent photocurrent density reveals that MoO3/γ-In2Se3 films have effective electron-hole separation. Our finding suggests that MoO3/γ-In2Se3-based heterostructure photoanode can enhance light harvesting capacity and suppresses carrier recombination rate, eventually boosting PEC performance. Moreover, these results encourage the development of highly efficient photoelectrodes based on heterostructures for solar water-splitting applications. [ABSTRACT FROM AUTHOR]

Indium selenide (γ-In2Se3) films were prepared using RF magnetron sputtering. Influence of deposition time on structural, optical, morphological, and photoelectrochemical (PEC) performance was studied. Formation of γ-In2Se3 is confirmed by low angle XRD, Raman spectroscopy, and XPS analysis. Surface morphology investigated using FE-SEM shows that γ-In2Se3 films are uniform and have a dense grain structure, without cracks and holes. Optical properties show that γ-In2Se3films absorb mainly in the UV region, and the bandgap energy decreases from 2.81 to 2.27 eV as deposition duration increases. Conduction and valance band-edge potential values show that γ-In2Se3 films are suitable for photoelectrochemical hydrogen evolution. PEC activity of γ-In2Se3 photoanodes was evaluated using linear sweep voltammetry (LSV), and there was an increase in photocurrent density with deposition time. Electron impedance spectroscopy (EIS) analysis revealed that γ-In2Se3 photoanodes had high charge transfer resistance, and it decreases with deposition time, which leads to improved PEC performance. Investigation of Mott Schottky's (MS) results shows a shifting of flat band potential towards negative potential, suggesting movement of fermi level towards conduction band edge. Carrier density increases from 3.7 × 1019 cm−3 to 8.9 × 1020 cm−3 and depletion layer width of γ-In2Se3 photoanodes are found in the range of ~ 2.67–9.10 nm. The gradual increase in electron lifetime indicates a decrease in the recombination rate of photo-generated charge carriers. An increase in time-dependent photocurrent density reveals that γ-In2Se3 films have effective electron–hole separation. Our work demonstrates that γ-In2Se3 can be a probable candidate for PEC water splitting and opto-electronic applications. [ABSTRACT FROM AUTHOR]

Herein, we report the synthesis of ZnO nanorod films onto FTO (fluorine-doped tin oxide) substrates using the solution-processed electrodeposition method. As-synthesized ZnO nanorod films obtained from electrodeposition were modified to form zinc ferrite (ZnFe2O4) thin films by Fe incorporation through varying molar concentrations. The formation of ZnFe2O4 films was confirmed by XRD and Raman spectroscopy. FE-SEM analysis shows a significant change in the growth morphology with an increase in Fe molar concentration. UV-Visible spectroscopy analysis showed that with an increase in Fe molar concentration, the absorption edge in ZnFe2O4 films shifts towards a higher wavelength with a reduction in the direct band gap. Finally, the PEC properties of ZnFe2O4 photoanodes were investigated for water splitting. The highest photocurrent density of ~ 353 μA/cm2 has been observed for ZnFe2O4 photoanode prepared at 2.0 M. Shift of flat band potential shift from −0.25 to −0.61 V with an increase in Fe molar concentration indicates a shift in the Fermi level towards the conduction band, which leads to an efficient charge transfer process across the electrolyte. Furthermore, increased carrier density and decreased depletion width with increased Fe molar concentration suggest easier diffusion of photo-generated charge carriers. The obtained results demonstrate that ZnFe2O4 can be a promising candidate for efficient PEC water splitting over the traditional ZnO photoanode. [ABSTRACT FROM AUTHOR]

Zinc oxide nano-sheets (ZNS) loaded with Zeolitic Imidazole Framework 8 (ZIF8) nanocrystals, i.e. (ZNS@ZIF8) thin films, were successfully synthesized using electrodeposition and facile chemical bath deposition (CBD) for photoelectrochemical (PEC) splitting of water. The formation of ZNS nano-sheets and ZIF8 nano-crystals has been confirmed by field emission scanning electron microscopy (FE-SEM), low angle X-ray diffraction (XRD), micro-Raman spectroscopy, and Fourier transform infrared (FTIR) spectroscopy analysis. PEC activity of ZNS@ZIF8 photoanodes was evaluated using the linear sweep voltammetry (LSV) technique, and the photocurrent density is significantly enhanced when ZNS are decorated with ZIF8 nanocrystals. Electrochemical impedance spectroscopy (EIS) revealed that ZNS@ZIF8 had low charge transfer resistance compared to pristine ZNS counterparts. This led to considerably improved PEC performance of ZNS@ZIF8. Mott–Schottky (M–S) analysis of ZNS and ZNS@ZIF8 revealed a shift of flat band potential for the ZNS and ZNS@ZIF8 photoanodes, respectively. The shift of flat band potential indicates a clear shift in the Fermi level towards the conduction band, leading to an efficient charge transfer process across the electrolyte. The carrier density of ZNS and ZNS@ZIF8 photoanodes increases from 3.67 × 1019 cm−3 to 4.11 × 1020 cm−3. The enhanced applied bias photon conversion efficiency (ABPE) of ZNS@ZIF8 photoanodes suggests that ZNS@ZIF8 can be a prospective candidate for PEC and optoelectronic applications. [ABSTRACT FROM AUTHOR]

In photoelectrochemical (PEC) water splitting, visible light active semiconductors exhibit high conversion efficiency as they are more responsive. Herein, we have realized novel Bi 2 S 3 –In(OH) x S y nanoarchitectures for efficient PEC water splitting. We have electrodeposited bismuth vanadate (BiVO 4) thin films, and In and S were incorporated via hydrothermal treatment, leading to the formation of novel Bi 2 S 3 –In(OH) x S y nanoarchitectures. Bi 2 S 3 –In(OH) x S y plane view field emission scanning electron microscope shows a novel patty-packed structure covered with some urchin-like structures, implying a strong surface effect. Electron Impedance spectroscopy (EIS) was employed for impedance measurements. Flat band potential and carrier concentration were determined from Mott-Schottky (MS) plots. The realized novel Bi 2 S 3 –In(OH) x S y nanoarchitecture-based photoanodes exhibited a remarkable photocurrent density of 7.77 mA/cm2 at a bias voltage of 1.2 V/RHE under 1.5 AM illumination (1000 W/m2). The heterojunction nanoarchitectures have a reduction in the surface states of the nanocrystal, low lattice misfit, and quick charge transfer, which leads to effective PEC activity. The ABPE for the novel Bi 2 S 3 –In(OH) x S y nanoarchitecture-based photoanodes is 4.5% at 0.6 V vs. RHE in an electrolyte solution containing 0.1 M Na 2 SO 4. The results are encouraging and suggest that the Bi 2 S 3 –In(OH) x S y nanoarchitectures-based photoanodes can be a prospective material for efficient solar-to-hydrogen generation devices. [Display omitted] • Photoelectrochemical water splitting by Bi 2 S 3 –In(OH) x S y nanoarchitectures. • New class of visible light-responsive metal hydroxide. • Remarkable photocurrent density. • Recued surface states, low lattice misfit, and quick charge transfer. • Prospective material for efficient solar-to-hydrogen generation devices. [ABSTRACT FROM AUTHOR]