Photoelectrochemical and photocatalytic activity of tungsten doped TiO2 nanotube layers in the near visible region (original) (raw)
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One-Step Formation of WO3-Loaded TiO2 Nanotubes Composite Film for High Photocatalytic Performance
High aspect ratio of WO3-loaded TiO2 nanotube arrays have been successfully synthesized using the electrochemical anodization method in an ethylene glycol electrolyte containing 0.5 wt% ammonium fluoride in a range of applied voltage of 10-40 V for 30 min. The novelty of this research works in the one-step formation of WO3-loaded TiO2 nanotube arrays composite film by using tungsten as the cathode material instead of the conventionally used platinum electrode. As compared with platinum, tungsten metal has lower stability, forming dissolved ions (W 6+ ) in the electrolyte. The W 6+ ions then move towards the titanium foil and form a coherent deposit on titanium foil. By controlling the oxidation rate and chemical dissolution rate of TiO2 during the electrochemical anodization, the nanotubular structure of TiO2 film could be achieved. In the present study, nanotube arrays were characterized using FESEM, EDAX, XRD, as well as Raman spectroscopy. Based on the results obtained, nanotube arrays with average pore diameter of up to 74 nm and length of 1.6 µm were produced. EDAX confirmed the presence of tungsten element within the nanotube arrays which varied in content from 1.06 at% to 3.29 at%. The photocatalytic activity of the nanotube arrays was then investigated using methyl orange degradation under TUV 96W UV-B Germicidal light irradiation. The nanotube with the highest aspect ratio, geometric surface area factor and at% of tungsten exhibited the highest photocatalytic activity due to more photo-induced electron-hole pairs generated by the larger surface area and because WO3 improves charge separation, reduces charge carrier OPEN ACCESS Materials 2015, 8 2140 recombination and increases charge carrier lifetime via accumulation of electrons and holes in the two different metal oxide semiconductor components.
Electrochemical characterization of TiO2/WOx nanotubes for photocatalytic application
Nanoscale Research Letters, 2014
TiO 2 /WO x nanotubes have unique photo-energy retention properties that have gathered scientific interest. Herein, we report the synthesis, morphological characterization, and the electrochemical characterization of TiO 2 /WO x nanotubes compared with pure TiO 2 nanotubes, prepared by anodization technique. Significant structural differences were not observed in TiO 2 /WO x nanotubes as observed by using scanning electron microscopy and transmission electron microscopy. The charge transfer resistance of TiO 2 /WO x before and after photo irradiation determined by using electrochemical impedance spectroscopy proves the inherent energy retention property which was not observed in pure TiO 2 nanotubes.
WO3 as Additive for Efficient Photocatalyst Binary System TiO2/WO3
Latvian Journal of Physics and Technical Sciences, 2021
Two different methods of synthesis of TiO2/WO3 heterostructures were carried out with the aim to increase photocatalytic activity. In this study, anodic TiO2 nanotube films were synthesized by electrochemical anodization of titanium foil. WO3 particles were applied to anodic Ti/TiO2 samples in two different ways – by electrophoretic deposition (EPD) and insertion during the anodization process. Structural and photocatalytic properties were compared between pristine TiO2 and TiO2 with incorporated WO3 particles. Raman mapping was used to character-ise the uniformity of EPD WO3 coating and to determine the structural composition. The study showed that deposition of WO3 onto TiO2 nanotube layer lowered the band gap of the binary system compared to pristine TiO2 and WO3 influence on photo-electrochemical properties of titania. The addition of WO3 increased charge carrier dynamics but did not increase the measured photo-current response. As the WO3 undergoes a phase transition from monoc...
Topics in Catalysis, 2008
In this study, the photocatalysis of hybrid WO 3 / TiO 2 films with different loadings of WO 3 were investigated with and without potential bias. It was clearly indicated that hybrid WO 3 /TiO 2 films show less photoreactivity under only UV-irradiation, while more effective photocatalysis under potential bias than either TiO 2 or WO 3 by themselves, their photocatalytic performance depending on the loadings of WO 3. In particular, a hybrid WO 3 /TiO 2 film involving an amorphous-like WO 3 phase plays a significant role in an enhancement of the electrochemically assisted photocatalysis.
A Novel Solar Driven Photocatalyst: Well-Aligned Anodic WO 3 Nanotubes
International Journal of Photoenergy, 2013
Well-aligned anodic tungsten trioxide (WO 3 ) nanotubes were successfully synthesized by anodization of W foil at 40 V in a bath with electrolyte composed of 1 M of sodium sulphate (Na 2 SO 4 ) and 0.5 wt% ammonium fluoride (NH 4 F). The effect of electrochemical anodization times on the formation mechanism of anodic WO 3 nanotubular structure was investigated. It was found that minimum of 15 min is required for completing transformation from W foil to WO 3 nanotubular structure with an average diameter of 50 nm and length of 500 nm. The photocatalytic ability of the samples was evaluated by degradation of methyl blue (MB) dye. The results indicate that the surface morphology of anodic WO 3 affected the photocatalytic MB degradation significantly under solar illumination.
Catalysis Today, 2013
Aiming at producing TiO 2-based photocatalytic materials with reduced charge carriers recombination, WO 3-TiO 2 mixed oxides were synthesized by a sol-gel method employing either an inorganic salt, Na 2 WO 4 , or an organic alkoxide, W(OC 2 H 5) 6 , as tungsten precursor, with different W/Ti ratios. The soobtained materials were characterized by XRPD, BET, UV-vis reflectance, XPS and EDX analyses and their photoactivity was tested under UV-visible irradiation in both the mineralization of formic acid in aqueous suspension and the gas phase oxidation of acetaldehyde. Both photoactivity results and photocurrent measurements point to a superior performance of photocatalysts obtained from the organic precursor with an optimal tungsten content (3%). The formation of an intimately mixed oxide, as revealed by XRPD analysis, results in photoactivity higher than that of pure TiO 2 , and also of benchmark P25 TiO 2 , consequent to a better charge separation due to the migration of photoproduced holes from WO 3 domains to TiO 2 and of photopromoted electrons in the opposite direction. The persistence of pure anatase phase in W-containing photocatalysts also after calcination at 700 • C and their higher surface area with respect to pure TiO 2 also contribute in increasing the photocatalytic activity of the WO 3-TiO 2 mixed oxides.
2018
The novelty of this research works in the two-step formation of tungsten oxide (WO3)-loaded TiO2 nanotube arrays composite film by study the optimum conditions of electrodeposition of WO3 nanoparticles on TiO2 nanotubes arrays based on their photo-activity performance. The W have been incorporated from a sodium tungstate-based aqueous electrolyte containing from 0.2 M sodium tungstate (Na2WO4) with addition of 0.13 M hydrogen peroxide (30%) and drops from H2SO4 up to get pH = 1; it accumulates to form a self independent structure of WO3 on the surface of the nanotubes. WO3 was deposited for several times intervals at room temperature and annealed at 350 ºC for 30 minutes. TiO2 nanotubes (TNTA) were successfully grown by anodizing of titanium foil (Ti) in organic (98% vol., ethylene glycol, 2 vol.% Di water and 0.5 wt% ammonium fluoride and acidic (0.5M phosphoric acid and 0.14M sodium fluoride) electrolyte. The possible growth of TiO2 nanotubes in the applied potential at 20V for 45 minutes was investigated. It were found such electrochemical condition resulted in formation of nanotube with average diameter 50 & 120 nm and the length 3.5 & 0.6 µm for organic and acidic electrolytes respectively. The anodized samples were annealed at 500 ºC in N2 gas for 3 hours. The structural, morphology and composition of TiO2 nanotubes and WO3/TiO2 nanotube were characterized with XRD, FESEM and EDX. FESEM results of the nanotubular arrays showed uniform arrays of titania nanotubular and showed. EDX results showed trace of tungsten has been incorporated into TiO2. The influences of tungsten content on the photocurrent densities of WO3/TiO2 nanotubular photoanodes were investigated by recording current-potential profiles. The preliminary results indicated that the WO3/TiO2 produced showed good photocurrent densities due to the behavior of W 6+ ions which allows to electron traps that suppress electron-hole recombination and exploit the lower band gap of material to produce a water splitting process by increasing the charge separation and extending the energy range of photo-excitation for the system.
Catalysis Today
The "build-up" methodology, the importance of the order of the semiconductor layers in WO 3-TiO 2 /MWCNT composite materials was studied in terms of the applied synthesis pathway, morpho-structural parameters (mean crystallite size, crystal phase composition, morphology) and photocatalytic efficiency (using oxalic acid as model pollutant). The appearance of TiWO x phase in the composites contributed to the enhancement of the photocatalytic efficiencies, as different synthesis approaches led to different crystal phase compositions. Although, it was proven that a beneficial phase's presence can be hindered if an excess of MWCNT or WO 3 was applied. As the ratio of the mentioned materials was reduced, active composites were obtained, but the previously noticed TiWO x disappeared. Therefore, it was proven, that in the case of WO 3-TiO 2 /MWCNT nanocomposite system several photocatalytic activity enhancement factors can be introduced, but not simultaneously (the disappearance of TiWO x at low MWCNT and WO 3 contents and the appearance of highly crystalline anatase).