Photo-assisted Deposition Research Articles

Preparation of cobalt coated TiO2 and WO3–TiO2 nanotube films via photo-assisted deposition with enhanced photocatalytic activity under visible light illumination

Highly ordered TiO2 and WO3–TiO2 nanotubes were prepared by one-step electrochemical anodizing method and cobalt has been successfully deposited on these nanotubes by photo-assisted deposition process. The morphology, crystal structure, elemental composition and light absorption capability of samples were characterized by field emission scanning electron microscope, X-ray diffraction, energy dispersive X-ray spectrometer and ultraviolet–visible spectroscopy methods. All cobalt loaded samples show an appearance of red shift relative to the unloaded samples. The degradation of methylene blue was used as a model reaction to evaluate the photocatalytic activity of these novel visible-light-responsive photocatalysts. Results showed that the photocatalytic activity of bare WO3–TiO2 samples is higher than that with undoped TiO2 sample. Compared with unmodified TiO2 and WO3–TiO2, the Co/TiO2 and Co/WO3–TiO2 samples exhibited enhanced photocatalytic activity in the degradation of methylene blue. Kinetic research showed that the reaction rate constant of Co/WO3–TiO2 is approximately 2.26 times higher than the apparent reaction rate constant of bare WO3–TiO2. This work provides an insight into designing and synthesizing new TiO2–WO3 nanotubes-based hybrid materials for effective visible light-activated photocatalysis. The catalysts prepared in this study exhibit industrially relevant interests due to the low cost and high photocatalytic activity.

Efficient solar water-splitting using Cu/WO3-TiO2 photoanodes prepared by anodizing and photoassisted deposition method

WO3-TiO2 nanotube films on pure titanium substrates were successfully fabricated by one-step electrochemical anodizing and copper deposited on these nanotubes by photo-assisted deposition method. The morphology, structure and composition of synthesized films were characterized by SEM, XRD, EDX and UV-vis, respectively. Results showed that the films have the ordered nanotubes with average pore diameter of 70–100 nm and wall thickness of 20–25 nm. Diffuse reflectance spectra showed an increase in the visible absorption relative to bare WO3-TiO2 nanotubes. Photocatalytic activity of samples was evaluated by testing the solar water splitting. After irradiated under xenon light illumination for 360 min, the total amount of H2 evolved on the Cu/WO3-TiO2 sample was 55 mL/cm2, which is approximately 6.9 times higher than that on the bare WO3-TiO2 (8 mL/cm2). The catalysts prepared in this study exhibit industrially relevant interests due to the low cost and high photocatalytic activity.

In situ photo-assisted deposition and photocatalysis of ZnIn2S4/transition metal chalcogenides for enhanced degradation and hydrogen evolution under visible light.

The effective immobilization of a transition chalcogenide co-catalyst via an in situ aqueous photo-assisted deposition technique has shown great accessibility to complex ZnIn2S4 host hierarchical nanostructured materials with homogeneous distribution. The complementary photo-assisted deposition readily deposits finely-dispersed co-catalyst particles and simultaneously generates photocatalytic hydrogen. Another added advantage is that the photo-assisted deposition of the co-catalyst does not compromise the crystal structure or the integrity of the host photocatalyst, hence offering a better alternative to the doping technique. A systematic study of various transition metal chalcogenide co-catalysts and optimization of wt% MoS2, CuS and Ag2S loadings were demonstrated. Among them, the ZnIn2S4/MoS2 composite exhibits exceptional photocatalytic hydrogen production and stability as well as superior MO degradation under visible light irradiation. The present methodology is expected to be extendable to various transition metal oxides/chalcogenides since ionic derivatives exhibit high affinity to a variety of materials under photoirradiation.

Photo-assisted electrodeposition of manganese oxide on TaON anodes: effect on water photooxidation capacity under visible light irradiation

Photo-assisted deposition of MnOxon the TaON anodes enhances activity and stability during water photooxidation.

Cobalt modified tungsten–titania nanotube composite photoanodes for photoelectrochemical solar water splitting

Cobalt modified tungsten–titania nanotubes (Co/WTNs) with different amounts of cobalt were prepared by two methods; photo-assisted deposition and one-step electrochemical anodizing method. The morphology, crystallinity, elemental composition and light absorption capability of samples were characterized by field emission scanning electron microscope, X-ray diffraction, energy dispersive X-ray spectrometer and ultraviolet–visible spectroscopy methods. All cobalt loaded samples show a red shift relative to the unloaded samples. The photo-catalytic water splitting was used as a model reaction to evaluate the photo-catalytic activity of the obtained samples. The photo-catalytic performance was examined under xenon lamp irradiation in 1 M NaOH electrolyte. All cobalt modified samples showed photo-catalytic properties better than that for the bare WTNs and bare TiO2 samples. The total amount of H2 evolved on the Co/WTNs2 sample was 1.9 times higher than that on the bare TiO2 sample. The catalysts prepared in this study exhibit industrially relevant interests due to the low cost and high photocatalytic activity. These new photoanodes are highly promising photoanodes for photo-catalytic hydrogen production.

Solar water-splitting using palladium modified tungsten trioxide-titania nanotube photocatalysts

Palladium modified tungsten trioxide-titania nanotubes (WOTNs) with different amounts of palladium were prepared by two methods; photo-assisted deposition and one-step electrochemical anodizing method. The resulting samples were characterized by X-ray diffraction, field emission scanning electron microscope, ultraviolet–visible spectroscopy and energy dispersive X-ray spectrometer methods. The photocatalytic water splitting was used as a model reaction to evaluate the photocatalytic activity of the obtained samples. The photocatalytic performance was examined under xenon lamp irradiation in 1 M NaOH electrolyte. All palladium modified samples showed photocatalytic properties superior to that for the bare WOTNs sample. The total amount of H2 evolved on the Pd/WOTNs2 sample was 2.5 times higher than that on the bare WOTNs sample. These new photoanodes showed enhanced high photocurrent density with good stability and are highly promising photoanodes for photocatalytic hydrogen production.

Photocatalytic Hydrogen Production from Glycerol-water over Metal Loaded and Non-metal Doped Titanium Oxide

Modifications of the TiO2 P25 photocatalyst with metals: Platinum (Pt), Copper (Cu) and nonmetal: Nitrogen (N) doping to produce Hydrogen (H2) from a glycerol-water mixture have been investigated. The metals (Cu and Pt) were loaded into Titanium Dioxide (TiO2 ) surface by employing an impregnation and Photo-Assisted Deposition (PAD) method, respectively. As prepared the metal doped TiO2 photocatalyst was then dispersed into an ammonia solution to obtain N-doped photocatalysts. The modified photocatalysts were characterized by X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), and Ultraviolet-Visible Diffuse Reflectance Spectroscopy (UV-Vis DRS). XRD patterns indicated that the modified TiO2 photocatalysts have a nano-size crystallite range of 16-23 nm, while the DRS analysis showed that the doping of both metal and non-metal into TiO2 photocatalysts could effectively shift photon absorption to the visible light region. The optimum Cu loading of Cu-N-TiO2 was found to be 5%, resulting in a 10 times higher H2 production improvement level when compared to unloaded TiO2, even though this is still considered to be inferior compared to that of a 1% Pt loading, which results in a 34 times higher level than an unmodified TiO2 photocatalyst. The effect of glycerol concentrations on hydrogen production has also been studied. This method offers a promising technology to find renewable and clean energy by using cheap materials and a simple technology.

New Method for the Synthesis of Ru Nanoparticles Using Photoexcited Fullerene C60-containing Mesoporous Silica as a Catalyst Support

Abstract A new photoassisted deposition (PAD) method using fullerene C60 is developed. Photoexcited fullerene C60 introduced within the mesopore of SBA-15 acts as an anchor to reduce Ru3+ ions to the highly dispersed Ru metal with a narrow size distribution. Such uniform Ru nanoparticles (NPs) show high catalytic activity for dehydrogenation of ammonia borane than the sample prepared by conventional impregnation method.

Synthesis and characterization of Pt/AgVO3 nanowires for degradation of atrazine using visible light irradiation

A hydrothermal method was used to prepare β-AgVO3 nanowire, a photo-assisted deposition (PAD) method was used to prepare Pt/β-AgVO3 nanowires. β-AgVO3 and Pt/β-AgVO3 nanowires were characterized using XRD, BET, UV–Vis spectroscopy, Pl, TEM, and XPS techniques. The results reveal that platinum was present as platinum metal and it is well dispersed on the surface of β-AgVO3 nanowire. The photocatalytic degradation of atrazine under visible light irradiation was used to measure the photocatalytic performance of the β-AgVO3 and Pt/β-AgVO3 nanowires. The photocatalytic activity of Pt/β-AgVO3 nanowires have higher photocatalytic activity than β-AgVO3 nanowire. The reason for the high photocatalytic activity of Pt/β-AgVO3 nanowires may be due to the synergic effect between Pt and β-AgVO3.

Modification of C/TiO2@MCM-41 with nickel nanoparticles for photocatalytic desulfurization enhancement of a diesel fuel model under visible light

Ni metal nanoparticles were attached on the C/TiO2@MCM-41 (CTM-41) via facile and fast method based on dispersing of C/TiO2@MCM-41 in aqueous solution containing nickel ions by ultrasonic bath. Then, for the first time, the Ni ions were converted to Ni nanoparticles under UV light (photo-assisted deposition, PAD method), without using reducing agents and hydrogen gas. This process was carried out under the relatively mild conditions. The results showed that Ni (II) was reduced to Ni metallic nanoparticle in the size of about 2.7nm on the surface of CTM-41 (Ni/CTM-41) with specific surface area of 754.37m2g−1. The photocatalytic ultra-deep desulfurization of a fuel-like n-octane containing dibenzothiophene (DBT) was conducted over the Ni/CTM-41 nanophotocatalyst. Using this method, the total sulfur content efficiently decreased under mild conditions in one phase and without using an oxidant. The synthesized Ni/CTM-41 (3% Ni) exhibited the maximum photocatalytic desulfurization of DBT for all different ratios of Si/Ti. In contrast, the synthesized CTM-41 (without Ni) exhibited the maximum photocatalytic desulfurization of DBT only for minimum ratio of Si/Ti. The Ni/CTM-41 was characterized by several techniques including N2 adsorption–desorption isotherms, XRD, TEM, and atomic absorption spectroscopy techniques. The results confirmed that Ni was highly dispersed on the support phase. The GC–MS analysis confirmed the photocatalytic removal of DBT. Based on the experimental results, it is proposed that the hydroxyl radical and hole have key role in the photocatalytic desulfurization process.

In-situ photo-assisted deposition of silver particles on hydrogel fibers for antibacterial applications.

Silver nanoparticles (AgNPs) have attracted intensive research interest and have been recently incorporated in polymers, medical devices, hydrogels and burn dressings to control the proliferation of microorganisms. In this study a novel silver antibacterial coating was deposited for the first time on hydrogel fibers through an in-situ photo-chemical reaction. Hydrogel blends obtained by mixing different percentages of silver-treated and untreated fibers were characterized by thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). Four different fluids, such as phosphate buffered saline (PBS), simulated body fluid (SBF), chemical simulated wound fluid (cSWF), and deionized water (DI water), were used for evaluating the swelling properties. The results obtained confirmed that the presence of silver did not affect the properties of the hydrogel. Moreover, the results obtained through inductively coupled plasma mass spectrometry (ICP-MS) demonstrated very low silver release values, thus indicating the perfect adhesion of the silver coating to the substrate. Good antibacterial capabilities were demonstrated by any hydrogel blend on Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) through agar diffusion tests and optical density readings.

Photocatalytic degradation of Congo red under visible light irradiation using Pd–Bi3.84W0.16O6.24 nanocomposite

A hydrothermal method was used to prepare Bi3.84W0.16O6.24 nanoparticles, and a photo-assisted deposition method was used to deposit palladium into the surface of Bi3.84W0.16O6.24 nanoparticles. BET, XRD, XPS, Pl, UV–Vis and TEM measurements were used to characterize the Bi3.84W0.16O6.24 and Pd/Bi3.84W0.16O6.24 nanoparticles. The photocatalytic oxidation of Congo red under visible light irradiation was used to determine the photocatalytic performance of the prepared nanoparticles. The results demonstrated that the palladium was well dispersed on the surface of the Bi3.84W0.16O6.24 nanoparticles. Additionally, the surface area of the Pd/Bi3.84W0.16O6.24 nanoparticles was smaller than that of the Bi3.84W0.16O6.24 nanoparticles because some of the pores of the Bi3.84W0.16O6.24 nanoparticles were blocked by the deposited Pd metal. The Pd/Bi3.84W0.16O6.24 nanoparticles (0.3wt.%) exhibited the lowest band gap and the highest photocatalytic activity for the oxidation of Congo red. The photocatalytic performance of the 0.3wt.% Pd/Bi3.84W0.16O6.24 nanoparticles was stable after the nanoparticles were reused five times for the oxidation of Congo red.

Visible light photocatalytic synthesis of aniline with an Au/LaTiO3 nanocomposites

An ultrasonic method was used to prepare LaTiO3 nanoparticles and a photo-assisted deposition method was used to loading gold into surface of LaTiO3. The samples obtained were characterized using a photoluminescence emission spectra, X-ray photoelectron spectroscopy, transmission electron microscopy, ultraviolet and visible light spectroscopy, surface area measurements and X-ray diffraction. In addition, photocatalytic activity of LaTiO3 and Au/LaTiO3 samples has been tested under visible light irradiation for reduction of nitrobenzene into aniline. XPS results reveal that gold was present as metallic gold by the presence of two peaks at 87.7eV and 84.0eV. The UV–Vis results reveal that loading of Au into LaTiO3 surfaces lead to a red shift. The maximum photocatalytic reduction efficiency (100%) was obtained using 0.3wt.% Au/LaTiO3 nanocomposites after 90min a reaction time. The Au/LaTiO3 nanocomposites can be recycled for the first five cycles without loss of photocatalytic activity.

Visible light photocatalytic reduction of nitrobenzene using Ag/Bi2MoO6 nanocomposite

The hydrothermal method was used to prepare Bi2MoO6 nanoparticles, and photo-assisted deposition method (PAD) was used to doped silver into Bi2MoO6 surface. Different characterization techniques were used to characterize the produced Bi2MoO6 and Ag/Bi2MoO6 nanoparticles, such as for the surface area measurement, X-ray diffraction, photoluminescence emission spectra, transmission electron microscopy, ultraviolet and visible spectroscopy, and X-ray photoelectron spectroscopy. Photocatalytic reduction of nitrobenzene under visible light irradiation was used to measure the photocatalytic performance of Bi2MoO6 and Ag/Bi2MoO6 nanoparticles. The results reveal that doping of silver led to a shift of the absorption edge of Bi2MoO6 to high wavelength. 0.15wt% Ag/Bi2MoO6 has the highest photocatalytic activity. The highest photocatalytic activity of 0.15wt% Ag/Bi2MoO6 nanoparticle remains unchanged after being reused five times.

Preparation of Ag/TiO2/SiO2 films via photo-assisted deposition and adsorptive self-assembly for catalytic bactericidal application

The deterioration of water supply quality due to the waterborne bacteria is an environmental problem requiring the urgent attention. Due to the excellent and synergic antimicrobial capability, Ag-loaded TiO2 photocatalyst emerges as a feasible measure to guard the water. In our work, Ag nanoparticles have been prepared by the photoassisted reduction of AgNO3 on the TiO2 film fabricated by solution-based adsorptive self-assembly approach. The role of surfactant on the growth rate and size controlling of particles is also studied. In this connection, different kinds of surfactants, such as PVP, Tween-20, Tween-40 and so on, are applied in the system to investigate the formation of Ag nanoparticles. The surface profile and elemental analysis of Ag/TiO2/SiO2 films are examined by scanning electron microscopy and attached energy-dispersive X-ray spectroscopy, respectively. In the anti-bacteria detection, Ag nanoparticles are found to enhance the bactericidal efficiency strongly comparing with the pure TiO2 film under the same condition. In addition, by comparison with Ag/TiO2/SiO2 film in the dark environment as the reference experiment, UV–visible light plays a vital role in the improved bactericidal behavior, demonstrating the more efficient charge separation induced by metal silver. Because of the versatility of the method, the present photoreductive route is also exploited for the synthesis of Au nanoparticles on TiO2/SiO2 films. The corresponding photocatalytical detection results demonstrate the loading of Au nanoparticles can improve the photodegradation efficiency of methyl orange assigned to the similar electron-trapping effect to silver.

Enhancement of photocatalytic H2 evolution on ZnIn2S4 loaded with in-situ photo-deposited MoS2 under visible light irradiation

A new MoS2/ZnIn2S4 photocatalyst system has been designed for H2 evolution under visible light irradiation (λ>420nm), which was obtained by hydrothermal method to afford floriated ZnIn2S4 microspheres, and MoS2 co-catalyst was subsequently loaded onto the ZnIn2S4 surface via a facile in-situ photo-assisted deposition process. The effects of hydrothermal temperature, the In/Zn molar ratios on the crystal structure, morphology, optical property as well as photocatalytic activity have been investigated in detail. Especially, the loading amount and deposition method of the MoS2 co-catalyst are found to dramatically influence the photocatalytic activity of H2 evolution. Up to 8.047mmolh−1g−1 of H2 evolution rate has been achieved, 28 times higher than that of untreated ZnIn2S4. This work provides a new synthetic way to increase the photocatalytic activity of MoS2/ZnIn2S4.

Fabrication of metal nanoparticles in metal organic framework NH2-MIL-125 by UV photo-assisted methods for optimized catalytic properties

The influence of preparation method on the size, location and state of Pd nanoparticles were investigated within the pores of amine-functionalized metal organic frameworks NH2-MIL-125 using three different photo-assisted deposition methods and the conventional impregnation method. The oxidation state, size and location were determined by XAFS and TEM. The catalytic activity was studied for hydrolysis of ammonia borane (AB) at ambient temperature. The choice of solvent and hole scavenger/reducing medium directly influence the location and the reduction of the particles. Our study shows that the best sample is prepared by combining UV irradiation with a direct reduction by H2 gas, and finding the right amount solvent and solvent/hole scavenger ratio is necessary for successful NPs synthesis using only UV light irradiation.

Novel Ag/YVO4 nanoparticles prepared by a hydrothermal method for photocatalytic degradation of methylene-blue dye

A hydrothermal method was used to prepare YVO4 nanoparticles, and a photo-assisted deposition method was used to load Ag onto the YVO4. The photocatalytic performances of the prepared photocatalysts were tested by the degradation of methylene-blue dye using visible-light irradiation. The results indicate that the Ag is well-dispersed within the YVO4, and the surface area of the Ag/YVO4 is smaller than that of the YVO4 samples. The sample with 0.3wt% Ag/YVO4 has the highest activity for the removal of methylene-blue dye. The 0.3wt% Ag/YVO4 can be used five times without the loss of its photocatalytic activity.

Photocatalytic oxidation of methylene blue dye under visible light by Ni doped Ag2S nanoparticles

Ag2S nanoparticles were prepared using a hydrothermal method, and Ni was doped via a photo-assisted deposition method. The samples produced were characterized using different tools. Furthermore, the catalytic performance of the Ag2S and Ni/Ag2S samples was examined in the degradation of methylene blue dye under visible light. The UV–vis spectral analysis detected a red shift after loading of Ni. The maximum degradation efficiency achieved was 100% with 3wt% Ni/Ag2S as the photocatalyst after a 40-min reaction time. The catalyst could be reused without any loss in activity for the first five cycles.

Photocatalytic removal of cyanide by cobalt metal doped on TiO2–SiO2 nanoparticles by photo-assisted deposition and impregnation methods

Cobalt metal was doped on TiO2–SiO2 by photo-assisted deposition (PAD) and impregnation (Img) methods. The prepared catalysts were characterized by different techniques such as XRD, XAFS, TEM, and nitrogen adsorption analysis. Photocatalytic reactivity using Co/TiO2–SiO2 catalysts under visible-light conditions on the oxidation of cyanide with O2 reaction was evaluated. The results have shown notable photocatalytic activity of PAD-Co/TiO2–SiO2 which was 1.7 and 10 times higher than that of Img-Co/TiO2–SiO2 and TiO2–SiO2, respectively.