Khatcharin Wetchakun

Flame-Made Nb-Doped TiO2 Ethanol and Acetone Sensors

Undoped TiO2 and TiO2 nanoparticles doped with 1–5 at.% Nb were successfully produced in a single step by flame spray pyrolysis (FSP). The phase and crystallite size were analyzed by XRD. The BET surface area (SSABET) of the nanoparticles was measured by nitrogen adsorption. The trend of SSABET on the doping samples increased and the BET equivalent particle diameter (dBET) (rutile) increased with the higher Nb-doping concentrations while dBET (anatase) remained the same. The morphology and accurate size of the primary particles were further investigated by high-resolution transmission electron microscopy (HRTEM). The crystallite sizes of undoped and Nb-doped TiO2 spherical were in the range of 10–20 nm. The sensing films were prepared by spin coating technique. The mixing sample was spin-coated onto the Al2O3 substrates interdigitated with Au electrodes. The gas sensing of acetone (25–400 ppm) was studied at operating temperatures ranging from 300–400 °C in dry air, while the gas sensing of ethanol (50–1,000 ppm) was studied at operating temperatures ranging from 250–400 °C in dry air.

Enhancement of the Photocatalytic Performance of Ru-Doped TiO2 Nanoparticles

Pure TiO2 nanoparticles were synthesized by the modified sol-gel method using titanium tetraisopropoxide (TTIP) precursor dissolved in absolute ethanol. A pouch type cellophane membrane was employed as barrier between the precursor solution and the mixture of absolute ethanol (1:1 v/v) and distilled water with 0.5-1.0 % concentrated of ammonia in order to fix the reaction activity inside the pouch and control diffusion rate of hydrolysis and condensation reaction. The doping of TiO2 nanoparticles with 0.1, 0.2, 0.5, 1.0 and 2.0 at.% Ru was performed by the impregnation method using ruthenium acetyl acetonate in toluene as dopant. The properties of the all samples were characterized by X-ray diffraction (XRD), Brunauer, Emmett and Teller (BET)-specific surface area, Scanning electron microscopy-Energy dispersive spectroscopy (SEM-EDS) and transmission electron microscopy (TEM). The crystalline size of pure TiO2 and Ru-doped TiO2 nanopaticles were found to be in the range of 10-20 nm. The photocatalytic mineralization of formic acid, oxalic acid, sucrose and glucose was investigated using Degussa P25, pure TiO2 and Ru-doped TiO2 nanoparticles as photocatalysts in aqueous solutions under UVA irradiation. The rate of 50% mineralization of formic acid by 0.1 at.% Ru-doped TiO2 was 1.53 times and 1.34 times higher than that of pure TiO2 and Degussa P25, respectively showing the enhancement of the photocatalytic performance of TiO2 by doping with an optimum amount of ruthenium.

Influence of Cu doping on the visible-light-induced photocatalytic activity of InVO4

The photocatalytic degradation of methylene blue (MB) in the presence of pure InVO4 or a 0.5–5.0 mol% Cu-doped InVO4 composite under visible light irradiation (λ ≥ 400 nm) was studied in this research. The structural and photophysical properties of the as-prepared samples in the photocatalytic degradation process were investigated. The doping of InVO4 with a Cu photocatalyst results in wide absorption in the visible-light region and superior visible-light-driven photocatalytic activities in the degradation of MB. The results indicate that the InVO4 sample doped with 1.0 mol% of Cu shows the highest photocatalytic activity. The enhanced photocatalytic activity was attributed to the copper ions acting as trapping sites, facilitating the separation of charge carriers. The main active species for the degradation of MB were investigated to explain the enhancement of the photocatalytic performance of Cu-doped InVO4. A possible photocatalytic degradation pathway for aqueous MB dye and a charge transfer mechanism for Cu-doped InVO4 were proposed.

The effect of iron doping on the photocatalytic activity of a Bi2WO6–BiVO4 composite

Visible-light-driven Fe-doped Bi2WO6–BiVO4 composites have been synthesized via a hydrothermal method with varying nominal iron contents in the range of 0.5–5.0 mol%. The physicochemical properties of the obtained materials were characterized by X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET)-specific surface area, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), inductively coupled plasma-optical emission spectroscopy (ICP-OES), UV-vis diffuse reflectance spectroscopy (UV-vis DRS), and photoluminescence (PL) techniques. Methylene blue (MB) as probe pollutant was adopted to investigate the photocatalytic activity of all samples under visible light irradiation. The Fe-doped Bi2WO6–BiVO4 composites showed an enhanced photocatalytic activity for the degradation of MB under visible light, which was attributed to the iron ions acting as good electron and hole traps for facilitating the separation of charge carriers. Simultaneously, the high stability of the sample was also investigated by five successive photodegradation tests of MB under visible light. The relationship between the photocatalytic activities and the structures of Fe-doped Bi2WO6–BiVO4 composites was discussed. The possible photocatalytic mechanism of the composites was proposed to guide the further improvement of their photocatalytic performance.

Optimization of horizontal photocatalytic reactor for decolorization of methylene blue in water

AbstractThe prototype photocatalytic reactor was designed and then constructed in a horizontal scheme for testing the decolorization of methylene blue (MB) as a toxic organic model by UVA irradiation. The optimization of the photocatalytic reactor with a recycling system using TiO2 nanoparticles (P25) as photocatalysts was investigated in this work. The efficiencies on MB photocatalytic decolorization of three geometric photocollectors in the reactor: (i) parabolic through collector (PTC), (ii) compound parabolic collector (CPC), and (iii) flat-plate collector (FPC), including the presence and the absence of parabolic reflector cover the UVA tubular lamp as an artificial light source were compared. Excepting only the CPC, the experimental results indicate that the orientation of light rays using the reflector as a primary and the collector as a secondary, can improve on the photocatalytic efficiency of MB decolorization. In our case, the PTC with the presence of the reflector shows higher performance on t...

Highly efficient visible-light-induced photocatalytic activity of Bi{sub 2}WO{sub 6}/BiVO{sub 4} heterojunction photocatalysts

Abstract The Bi 2 WO 6 /BiVO 4 heterojunction photocatalysts were synthesized by hydrothermal method. Physical properties of the heterojunction photocatalyst samples were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques. The XRD results indicated that BiVO 4 retain monoclinic and tetragonal structures, while Bi 2 WO 6 presented as orthorhombic structure. The Brunauer, Emmett and Teller (BET) adsorption–desorption of nitrogen gas for specific surface area determination at the temperature of liquid nitrogen was performed on all samples. UV–vis diffuse reflectance spectra (UV–vis DRS) were used to identify the absorption range and band gap energy of the heterojunction photocatalysts. The photocatalytic performance of Bi 2 WO 6 /BiVO 4 heterojunction photocatalysts was studied via the photodegradation of methylene blue (MB) under visible light irradiation. The results indicated that the heterojunction photocatalyst at 0.5:0.5 mole ratio of Bi 2 WO 6 :BiVO 4 shows the highest photocatalytic activity.

Photodegradation of Phenol over Flame-Made Sn-Doped ZnO Nanoparticles

Undoped ZnO and 0.5−5.0 at.% Sn-doped ZnO nanoparticles were synthesized by flame spray pyrolysis (FSP) using zinc naphthenate and tin (II) 2-ethylhexanoate dissolved in xylene as the precursors under a 5/5 (precursor/oxygen) flame condition. UV-Vis absorption characteristics of the samples were investigated for understanding and relating with the physiochemical characteristics in photocatalytic applications. Kinetic analyzes indicated that the photodegradation rates of phenol could be approximated as pseudo-first-order and zero-order kinetics in the case of undoped ZnO and Sn-doped ZnO nanoparticles respectively, according to the Langmuir-Hinshelwood model. The effect of Sn doping revealed the deterioration of the phenol photodegradation performance over ZnO-based catalysts, possibly due to the formation of a deep state in the ZnO band gap energy.