The evolution of TiO2 nanotubular morphology, synthesized in a mixture of fluorinated ethylene glycol and glycerol electrolyte, was studied as a function of the anodization time. The samples were ...characterized by FEG-SEM, XRD, XPS, UV-Vis and EIS. The formation of single-or double-walled TiO2 nanotube structure can be efficiently controlled by the anodization time. For anodization times less than 30 minutes, a compact oxide layer is formed, followed by double-walled nanotube formation up to 120 minutes and single-walled nanotubes up to 240 minutes. XPS analyses show that the samples obtained with short anodization time have a high carbon content and oxygenated surface species compared to the longer-time anodized sample; however, binding energy peaks for Ti 2p remained invariant. The performances of TiO2 nanotubular photoelectrodes were evaluated in photoelectrochemical water splitting where TiO2 nanotubes anodized for 120 minutes presented the best performance that was related to their optimal morphology and charge transportation.
The development of efficient advanced functional materials is highly dependent on properties such as morphology, crystallinity, and surface functionality. In this work, hierarchical flowerlike ...nanostructures of SrTiO3 have been synthesized by a simple template-free solvothermal method involving poly(vinylpyrrolidone) (PVP). Molecular dynamics simulations supported by structural characterization have shown that PVP preferentially adsorbs on {110} facets, thereby promoting the {100} facet growth. This interaction results in the formation of hierarchical flowerlike nanostructures with assembled nanosheets. The petal morphology is strongly dependent on the presence of PVP, and the piling up of nanosheets, leading to nanocubes, is observed when PVP is removed at high temperatures. This work contributes to a better understanding of how to control the morphological properties of SrTiO3, which is fundamental to the synthesis of perovskite-type materials with tailored properties.
The growth of titanium dioxide nanotubes (TiO2) via anodization process depends on the controlling parameters such as applied potential, anodization time, and electrolyte composition. In the present ...work, the Taguchi method was applied to evaluate statistically the influence of the anodization parameters on the morphology of anodized TiO2 films. Mixture of ethylene-glycol and glycerol was used as an electrolyte and the settings of the experimental design were parameterized on the basis of four important anodization factors consisting of chemical pretreatment, amount of fluoride, water content and applied potential. Samples were characterized by XRD and FEG-SEM. Based on 4 variables at 3 different settings, full factorial plan requires 34 = 81 tests. In this work the experiment was designed on the basis of an L9 (34 ) orthogonal array (4 variables, 3 levels, 9 tests). The optimum conditions were found on the basis of smaller-is-better and larger-is-better analyses. The signal-to-noise ratio was employed to find optimal process parameters levels and to analyze the influence of these parameters on the tubular length, internal and external diameters and formation of nanograss on the film surface. Hence, it is clearly shown that the performance of TiO2 nanotubes can be evaluated by the Taguchi method.
Bi2S3 is a narrow bandgap (1.2 eV) semiconductor of interest for the construction of solar cells and photoelectrodes. While many researchers have reported on the use of Bi2S3 as a sensitizer for ...photoelectrodes, the photoelectrochemical (PEC) properties of pure Bi2S3 films are less documented. Here, phase pure Bi2S3 films (Bi/S elemental ratio of 0.66) were grown on FTO, ITO, Au, Mo substrates by electrochemical deposition of bismuth, followed by sulfurization in a single-zone tube furnace. The nanostructured Bi2S3 films are 5 ± 1 μm thick and crystallize in an orthorhombic Stibnite type structure. They have a bandgap of ∼1.24 eV based on UV-Vis diffuse reflectance and are n-type based on a negative surface photovoltage (SPV) signal. X-ray photoelectron spectroscopy (XPS) places the Fermi level at 0.95–0.91 eV above the valence band edge. According to X-ray diffraction the substrates have no influence on the crystallographic properties of the Bi2S3 films. However, the PEC properties of Bi2S3 films in 0.5 M Na2S(aq) are sensitively controlled by the Bi2S3/substrate interface. Under 100 mW cm−2 simulated solar (AM 1.5) illumination and 1.23 VRHE applied bias, Bi2S3 photoelectrodes produce anodic photocurrents of 9.3 mA cm−2, 6.1, 3.6 and 1.8 mA cm−2 for FTO, Mo, Au and ITO substrates, respectively, and photovoltages of 0.9–0.25 V. For FTO, the photocurrent reported here is among the best reported for phase pure Bi2S3 photoanodes. The lower performance of the other substrates is due to a Schottky barrier at the Bi2S3/substrate interface, which retards electron transfer. These findings explain why FTO is a preferred substrate for Bi2S3 photoanodes and they highlight the importance of matching substrate workfunction to the Bi2S3 Fermi level for efficient majority carrier extraction. Lastly, the work demonstrates the use of electrochemical deposition combined with single-zone furnace-based sulfurization as a pathway to form high-quality Bi2S3 films for solar energy conversion.
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•Evidencing the role of different oxidation states of Pt cocatalyst loaded onto BVO.•Control of photoreduction time ends up in different content of Pt0/PtOx onto BVO.•PtOx species ...improve the apparent quantum efficiency of BiVO4 compared to only Pt0.•Pt/PtOx shows a 58-fold increase in photodegradation rate constant vs. pristine BVO.•PtOx act as traps for the photoexcited electrons in the CB of BVO.
Monoclinic bismuth vanadate (BVO) has gained attention as a low-cost and promising visible light photocatalyst but suffers from fast charge carrier recombination. The present study reports the controlled photoreduction deposition of different Pt-based co-catalysts on the surface of BVO to address this drawback and brings a detailed discussion on the role of the oxidation state of Pt in determining the photoactivity of the photocatalysts. Results evidenced the presence of both metallic Pt and Pt oxides on the surface of BVO, with proportions that depended on the photoreduction time. The photocatalytic activity towards degradation of three model dyes revealed that platinum oxides (PtOx, x = 1 or 2) or a mixture of Pt0/PtOx species act out as better cocatalysts than Pt0, with an almost 4-fold higher apparent quantum yield for the optimized sample. The enhanced photoactivity of BVO/Pt/PtOx photocatalysts was attributed to their improved visible light absorption and enhanced charge carrier separation than pristine BVO or BVO/Pt. This study provides important insight into and a better understanding of the general photodeposition strategy employed to prepare semiconductor/metal (photo)catalysts on one hand and highlights the role of the oxidation state of deposited metal in determining the properties of composite (photo)catalysts on the other.
Here, using first-principles calculations based on density-functional theory, we propose a novel member of the two-dimensional (2D) transitional metal dichalcogenide family known as a Janus CrSSe ...monolayer (denoted as CrSSe-ML). The 2D CrSSe-ML has a hexagonal crystal structure. The calculated phonon band structure suggests Janus CrSSe-ML is dynamically stable, and formation energy indicates thermodynamic stability. At the equilibrium lattice constant, it is reported that 2D Janus CrSSe-ML is a non-magnetic semiconductor with a direct bandgap of 0.93 eV (K–K). We found that compressive biaxial strain induces no local magnetic moment, while in contrast the tensile biaxial strain of 12% induces a magnetic moment of 2 μB and half-metallicity which is robust up to 20%. Furthermore, we studied the ferromagnetic (FM) and antiferromagnetic (AFM) coupling between Cr atoms in CrSSe-ML and found that the FM state is favorable over AFM by the amount of energy of 0.007 meV, which is less than 0.03 eV, so no room-temperature ferromagnetism is possible. At the end, we added the H atom at the most preferable Se top-site in a Janus CrSSe-ML and found that hydrogenated Janus CrSSe-ML is magnetic and half-metallic at the equilibrium lattice constant. We further studied FM and AFM calculation by considering fully hydrogenated 4 × 4 × 1 supercell of a Janus CrSSe-ML. We used quantum Monte Carlo simulations (MC) to estimate the Curie temperature (T c) of hydrogenated CrSSe-ML under normal conditions. The calculated value of T c is 553.96 K using the quantum MC simulations. Our calculations predicted that the 2D Janus CrSSe-ML material is a promising candidate for spintronic device applications above room temperature.
Bi 2 S 3 is a narrow bandgap (1.2 eV) semiconductor of interest for the construction of solar cells and photoelectrodes. While many researchers have reported on the use of Bi 2 S 3 as a sensitizer ...for photoelectrodes, the photoelectrochemical (PEC) properties of pure Bi 2 S 3 films are less documented. Here, phase pure Bi 2 S 3 films (Bi/S elemental ratio of 0.66) were grown on FTO, ITO, Au, Mo substrates by electrochemical deposition of bismuth, followed by sulfurization in a single-zone tube furnace. The nanostructured Bi 2 S 3 films are 5 ± 1 μm thick and crystallize in an orthorhombic Stibnite type structure. They have a bandgap of ∼1.24 eV based on UV-Vis diffuse reflectance and are n-type based on a negative surface photovoltage (SPV) signal. X-ray photoelectron spectroscopy (XPS) places the Fermi level at 0.95–0.91 eV above the valence band edge. According to X-ray diffraction the substrates have no influence on the crystallographic properties of the Bi 2 S 3 films. However, the PEC properties of Bi 2 S 3 films in 0.5 M Na 2 S(aq) are sensitively controlled by the Bi 2 S 3 /substrate interface. Under 100 mW cm −2 simulated solar (AM 1.5) illumination and 1.23 V RHE applied bias, Bi 2 S 3 photoelectrodes produce anodic photocurrents of 9.3 mA cm −2 , 6.1, 3.6 and 1.8 mA cm −2 for FTO, Mo, Au and ITO substrates, respectively, and photovoltages of 0.9–0.25 V. For FTO, the photocurrent reported here is among the best reported for phase pure Bi 2 S 3 photoanodes. The lower performance of the other substrates is due to a Schottky barrier at the Bi 2 S 3 /substrate interface, which retards electron transfer. These findings explain why FTO is a preferred substrate for Bi 2 S 3 photoanodes and they highlight the importance of matching substrate workfunction to the Bi 2 S 3 Fermi level for efficient majority carrier extraction. Lastly, the work demonstrates the use of electrochemical deposition combined with single-zone furnace-based sulfurization as a pathway to form high-quality Bi 2 S 3 films for solar energy conversion.
Bi
2
S
3
is a narrow bandgap (1.2 eV) semiconductor of interest for the construction of solar cells and photoelectrodes. While many researchers have reported on the use of Bi
2
S
3
as a sensitizer ...for photoelectrodes, the photoelectrochemical (PEC) properties of pure Bi
2
S
3
films are less documented. Here, phase pure Bi
2
S
3
films (Bi/S elemental ratio of 0.66) were grown on FTO, ITO, Au, Mo substrates by electrochemical deposition of bismuth, followed by sulfurization in a single-zone tube furnace. The nanostructured Bi
2
S
3
films are 5 ± 1 μm thick and crystallize in an orthorhombic Stibnite type structure. They have a bandgap of ∼1.24 eV based on UV-Vis diffuse reflectance and are n-type based on a negative surface photovoltage (SPV) signal. X-ray photoelectron spectroscopy (XPS) places the Fermi level at 0.95-0.91 eV above the valence band edge. According to X-ray diffraction the substrates have no influence on the crystallographic properties of the Bi
2
S
3
films. However, the PEC properties of Bi
2
S
3
films in 0.5 M Na
2
S(aq) are sensitively controlled by the Bi
2
S
3
/substrate interface. Under 100 mW cm
−2
simulated solar (AM 1.5) illumination and 1.23 V
RHE
applied bias, Bi
2
S
3
photoelectrodes produce anodic photocurrents of 9.3 mA cm
−2
, 6.1, 3.6 and 1.8 mA cm
−2
for FTO, Mo, Au and ITO substrates, respectively, and photovoltages of 0.9-0.25 V. For FTO, the photocurrent reported here is among the best reported for phase pure Bi
2
S
3
photoanodes. The lower performance of the other substrates is due to a Schottky barrier at the Bi
2
S
3
/substrate interface, which retards electron transfer. These findings explain why FTO is a preferred substrate for Bi
2
S
3
photoanodes and they highlight the importance of matching substrate workfunction to the Bi
2
S
3
Fermi level for efficient majority carrier extraction. Lastly, the work demonstrates the use of electrochemical deposition combined with single-zone furnace-based sulfurization as a pathway to form high-quality Bi
2
S
3
films for solar energy conversion.
Bi
2
S
3
is a narrow bandgap semiconductor of interest for the construction of solar energy devices and can be synthesized by E-Chem/Sulfurization approach. The (photo)current from Bi
2
S
3
can be controlled by the substrate workfunction and its resistance.
•One-step electrochemical fabrication of counter-electrode for DSSc based on PPy.•Comparative physicochemical study of PPy films with and without AuNP incorporation.•Counter-electrode evaluation for ...efficiency, charge transport and e- decay rate.
A one-step electrochemical approach has been utilized to synthesize congo-red doped polypyrrole film embedded with gold nanoparticles (PPy-CR-AuNP). This study discusses for the first time the electrocatalytic properties of PPy-CR and PPy-CR-AuNP as counter-electrode in dye-sensitized solar cell (DSSC). Physicochemical characterizations of the films with and without AuNP have been presented. Both films/electrodes displayed excellent charge transfer abilities, as demonstrated by cyclic voltammetry analysis. Notably, PPy-CR-AuNP exhibited enhanced electron transfer kinetics with a 17% increase in electroactive surface area and improved efficiency in the I−/I3− redox pair activity compared to PPy-CR. Following extended storage under ambient conditions, PPy-CR-AuNP maintained a better mass transport and electron transfer at the electrode-electrolyte interface. The DSSC employing PPy-CR-AuNP as counter electrode exhibited a 12.5% enhancement in efficiency, lower electron transport time, higher electron recombination time and electron collection efficiency of up to 89%. Moreover, the electron decay rate was found to be 12.5% lower compared to the DSSC with PPy-CR electrode. These results demonstrated that PPy-CR-AuNP is an appropriate candidate for DSSC.
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In this research, hydrothermally synthesized tungsten trioxide (WO3) nanocomposites doped polyvinylpyrrolidone (PVP) and chitosan (CS) were studied. Various concentrations (3, 6, and 9 wt%) of PVP ...were doped into a fixed amount of binary system (CS-WO3) nanocomposites. PVP/CS polymers showed attractive attention because of their different structure, functionality, and architecture control as dopant to WO3. The PVP/CS encapsulates the WO3 (ternary composite), which controls crystallite size (band gap reduction), rapidly overcomes the recombination electron-hole pairs issues, and generates the active sites, resulting in improved catalytic and antimicrobial activity. The synthesized nanocomposites revealed significant catalytic efficiency and methylene blue (MB) dye depletion of 99.9 % in the presence of reducing agent (NaBH4) in neutral and acidic media. Antimicrobial effectiveness of produced nanostructures towards Escherichia coli (E. coli) pathogen at low and high concentrations were investigated by Vernier caliper in mm. Furthermore, to their microbicidal action, docking experiments of CS-doped WO3 and PVP/CS-doped WO3 nanostructures for DHFR and FabI of Escherichia coli suggested blockage of aforesaid enzymes as the plausible pathway.
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