RESUMEN
The enhancement of the photocatalytic performance of pristine WO3 was systematically adjusted due to its fast recombination rate and low reduction potential. A designed heterostructure photocatalyst was necessarily synthesised by Fe3+ metal ions doping into WO3 structure with and composition modification. In this study, we synthesised a retrievable Fe-doped WO3/SiO2 heterostructure using a surfactant-assisted hydrothermal method. This heterostructure was then employed as an effective photocatalyst for the removal of Cr(VI) under visible light irradiation. Enlarged photocatalytic reduction was observed over a synergetic 7.5 mol% Fe-doped WO3/SiO2-20 nanocomposite, resulting in dramatically increased activity compared with undoped WO3 and SiO2 nanomaterials under visible light illumination within 90 min. The presence of 7.5 mol% Fe3+ ion dopant in WO3 optimised electron-hole recombination, consequently reducing WO3 photocorrosion. After adding SiO2 nanoparticles, the binary WO3-SiO2 nanocomposite played roles as both adsorbent and photocatalyst to increase specific surface area. Thus, the 7.5 mol% Fe-doped WO3/SiO2-20 nanocomposite catalyst had more active sites on the surface of catalyst, and enhanced photocatalytic reduction was significantly achieved. The results showed 91.1% photocatalytic reduction over the optimum photocatalyst, with a photoreduction kinetic rate of 21.1 × 10-3 min-1, which was approximately four times faster than pristine WO3. Therefore, the superior optimal photocatalyst demonstrated reusability, with activities decreasing by only 9.8% after five cycles. The high photocatalytic performance and excellent stability of our photocatalyst indicate great potential for water pollution treatments.
RESUMEN
In the present work, the photocatalytic degradation of salbutamol [2-(tert-butylamino)-1-(4-hydroxyl-3-hydroxymethylphenyl)ethanol] under visible irradiation using Mn-doped TiO2 is investigated. The Mn-doped TiO2 nanoparticles were synthesized by the sol-gel method with ratios of 0.1, 0.2, and 0.3%. Significant characteristics, including the rutile/anatase phases ratio, specific surface area, and band gap energy, were due to the amount of Mn doping; the narrowest band gap energy of 2.80 eV was observed in 0.2% Mn-doped TiO2 with specific surface areas of 89.36 m2/g and 10.87/89.13 of rutile/anatase phases. The investigation involved salbutamol photocatalytic degradation, a kinetic study, and the identification of intermediate compounds. The results indicated that 0.2% Mn-doped TiO2 obtained the best salbutamol removal of 95% under an irradiation time of 180 min. Salbutamol slowly degraded to the intermediate compounds in the first 60 min (k = 0.0088 1/min), and these intermediate compounds were dramatically mineralized to small hydrocarbon fragments and carbon dioxide in the later irradiation times (k = 0.0179 1/min). According to the high-performance liquid chromatography-mass spectrometry (HPLC-MS) results, possible degradation pathways of salbutamol were proposed: 2-(tert-butylamino)-1-(3,4-dihydroxyphenyl)ethanone, 2-(tert-butylamino)-ethanol, and 2-(tert-butylamino)-1-(4-hydroxyl-3-hydroxymethylphenyl)ethanone were initially formed and then transformed to 2-(methylamino)-1-(3,4-dihydroxyphenyl)ethanone, 2-(tert-butylamino)-acetic acid, hydroquinone, and 1-(4-hydroxylphenyl)ethanol, respectively. The mineralization of all intermediate compounds was verified by 90% chemical oxygen demand (COD) reduction, and the effluent contained a relatively low COD concentration of 7.8 mg/L.
RESUMEN
A Cu(II)-quinoline complex immobilized on a silica support was prepared to enhance the degradation of dyes. Mesoporous silica functionalized with this Cu(II) complex was turned into a photo-Fenton-like catalyst. Various techniques were used to characterize the resulting material, and the catalytic activity was determined by the degradation of methylene blue (MB) under UV light irradiation. The Cu(II) ion was successfully coordinated to the quinoline ligand on a silica support. The dye degradation investigation has shown that 95% of the dye was degraded in 2.5 h. The active radical species involved in the reaction were OH⢠and O2 â¢-, suggesting that a peroxo complex intermediate might be formed during degradation processes.
RESUMEN
In this work, metal-doped titanium dioxide (TiO2) was synthesised with the aim of improving photocatalytic degradation and antimicrobial activities; TiO2 was doped with copper (Cu) ranging from 0.1 to 1.0 wt%. The physical and chemical properties of the Cu-doped TiO2 nanoparticles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), the Brunauer-Emmett-Teller method (BET) and diffuse reflection spectroscopy (DRS). The results revealed that the anatase phase of TiO2 was maintained well in all the Cu-doped TiO2 samples. No significant difference in the particle sizes or the specific surface areas was caused by increasing Cu doping. However, the band gap decreased continuously from 3.20 eV for undoped TiO2 to 3.12 eV for 1.0 wt.% Cu-doped TiO2. In addition, the 0.1 wt.% Cu-doped TiO2 displayed a much greater photocatalytic degradation of methylene blue (MB) and excellent antibacterial ability for Escherichia coli (E. coli) compared to undoped TiO2. On the other hand, the high Cu doping levels had negative impacts on the surface charge of nanoparticles and charge transfer for OH⢠generation, resulting in decreasing MB degradation and E. coli photokilling for 1.0 wt.% Cu-doped TiO2.
RESUMEN
Bismuth vanadate/coconut fiber (BiVO4/CF) composites were synthesized by coprecipitation and calcination methods. All catalysts used in this work were prepared by a simple coprecipitation method and fully characterized by means of XRD, SEM-EDS, PL, BET N2 adsorption, zeta potential, and UV-vis DRS. Degradation of indigo carmine (IC) under visible light irradiation was tracked by the UV-vis technique. It was documented that XRD patterns of BiVO4 and BiVO4/CF samples retained the monoclinic structure. From SEM, the CF sheets were visualized, covering the surface of BiVO4 particles. The specific surface area of the synthesized catalysts increased from 1.77 to 24.82 m2/g. The shift of absorption edge to a longer wavelength corresponded to a decrease in band gap energy from 2.3 to 2.2 eV. The photocatalytic degradation rate of the BiVO4/CF composite was five times higher than that of pristine BiVO4. Moreover, the photocatalyst can be separated and recycled with little change after the third times recycling. The improved activity of the composite resulted from the combination of the adsorption performance of the substrate CF and the photocatalytic activity of BiVO4. In addition, the position of the specific mechanism could occur via both the active species of superoxide radical and hydroxyl radical.
RESUMEN
WO3/CeO2 heterostructured nanocomposites containing different WO3 ratios (0.1, 0.3, 0.5, and 1.0 wt %) were synthesized by a precipitation method. The coupling of CeO2 and WO3 with a high specific surface area noticeably enhanced the photocatalytic activity of indigo carmine (IC) degradation under visible-light irradiation. The degradation rate constants (k) of 0.5 wt % WO3/CeO2 nanocomposites reached 4 and 5 times higher than those of CeO2 and WO3, respectively. Regarding the experimental results, the X-ray diffraction (XRD) patterns of the CeO2 spherical nanoparticles and rod-shaped WO3 were assigned to the cubic fluorite and orthorhombic phase structures, respectively. The increasing photocatalytic activity of nanocomposite samples could be attributed to the heterojunction of the photocatalysts with efficient charge separation and strong oxidative ability, which were confirmed by the photoluminescence spectra and diffuse reflectance spectrometry. The staggered heterojunction of the nanocomposite promoted efficient electron transfer and suppressed the recombination of photogenerated electrons and holes during the process.
RESUMEN
This work demonstrates a novel method to deposit an antibacterial TiO2 thin film on a polymer substrate at room temperature. A combination of sol-gel and photon assistance was used in the experiment in order to avoid any thermal processes of thin film crystallization. The morphological photograph of samples indicated that the TiO2 thin film was perfectly coated on the PVC substrate without any cracks or pinholes. Chemical analysis by EDS and XPS reported that the thin film consisted of titanium (Ti), oxygen (O), and carbon (C). The Raman spectrum proved that the thin film was the anatase phase of TiO2 and, furthermore, that it was contaminated with carbon remaining from the photon assistance process. In addition, the optical band gap of the thin film was 3.35 eV, suggesting that the photocatalytic activity of TiO2 should occur under UV-A radiation. The bacteria viability assay was examined using E. coli and S. typhimurium as indicator strains under UV-A irradiation (365 nm) at different times. The data from OD and CFU count revealed that >97% of bacteria were killed after 60 min of irradiation, and the bacteria were completely killed at 120 min for E. coli and 180 min for S. typhimurium.
RESUMEN
This work firstly demonstrates the ethanolamine (ETA)-assisted hydrothermal synthesis of BiVO4, with different ratios of exposed {110}/{010} planes and relates this to performance in photocatalytic oxidative coupling of benzylamine under visible light. {110}-dominant BiVO4 exhibits outstanding photocatalytic activity at room temperature owing to synergistic effects of largely exposed {110}-oxidative facet along with excellent charge generation and migration abilities, as evidenced by X-ray diffraction patterns, electrochemical impedance spectra, and photocurrent responses. The catalyst can successfully transform benzylamine derivatives to corresponding imines with selectivities of >85%, indicating a wide scope of amine substrates that can be used with the developed catalyst. Based on radical scavenging, spin-trapping EPR, and Mott-Schottky results, a plausible oxidative coupling mechanism via a O2--assisted route and band energy diagram of the catalyst are proposed. This work highlights the influence of ETA in controlling resultant exposed crystal facets of the final BiVO4, which is the main factor governing oxidative amine coupling activity. Importantly, the tunability of exposed {110}/{010} facet of BiVO4 controlled by ETA as well as a correlation between {110} facet and the coupling activity of benzylamine firstly disclosed in this work could be readily extended for designing functional catalysts with desired performances.
RESUMEN
The nanocomposite of BiVO4-based material has been synthesized by one-step solvent method. The morphological, physical, chemical properties of the nanocomposite have been investigated. The results revealed that the surface area of BiVO4, BiVO4/SiO2 and BiVO4/SiO2/GO was 11.13, 28.47 and 43.93 m2/g, respectively. The structural test by XRD proved that the nanocomposites were monoclinic phase of bismuth vanadate. Adsorption and photocatalytic degradation were two main mechanisms that strongly related to pollutant removal efficiency (i.e., methylene blue and phenol). The BiVO4/SiO2/GO nanocomposite obtained the greatest MB removal efficiency due to its high adsorption ability from high surface area, whereas the photocatalytic degradation was insignificant mechanism. In contrast, the relatively low adsorption ability of BiVO4/SiO2/GO nanocomposite was observed when the pollutant was phenol due to negative charge and high stability of phenoxide ions, then the photocatalytic degradation became the main mechanism for phenol removal. The phenol removal efficiency reached approximately 70% in 6 h with H2O2 assistance. The combination of SiO2 and GO improved the surface property of BiVO4-based photocatalyst, however the excessive combination ratio generated the excellent adsorbent material rather than the photocatalyst. Hence, the optimal combination ratio is essential to archive the greatest nanocomposite for photocatalytic application.
RESUMEN
Sb2O3-loaded NaWO4-doped WO3 nanorods were fabricated with varying Sb contents from 0 to 2 wt% by precipitation/impregnation methods and their p-type acetylene (C2H2) gas-sensing mechanisms were rigorously analyzed. Material characterization by X-ray diffraction, X-ray photoelectron spectroscopy, scanning transmission electron microscopy and nitrogen adsorption indicated the construction of short NaWO4-doped monoclinic WO3 nanorods loaded with very fine Sb2O3 nanoparticles. The sensors were fabricated by powder pasting and spin coating and their gas-sensing characteristics were evaluated towards 0.08-1.77 vol% C2H2 at 200-350 °C in dry air. The gas-sensing properties of the NaWO4-doped WO3 sensor with the optimum Sb content of 1 wt% showed the highest p-type response of â¼250.2 to 1.77 vol% C2H2, which was more than 20 times as high as that of the unloaded one at the best working temperature of 250 °C. Furthermore, the Sb2O3-loaded sensor offered high C2H2 selectivity against CH4, H2, C3H6O, C2H5OH, HCHO, CH3OH, C8H10, C7H8, C2H4 and NO2. Mechanisms responsible for the observed p-type sensing and response enhancement behaviors were proposed based on the NaWO4-doped WO3-Sb2O3 (p-n) heterointerfaces and catalytic spillover effects. Consequently, the Sb2O3-loaded NaWO4-doped WO3 nanorods have potential as alternative p-type gas sensors for selective and sensitive C2H2 detection in various industrial applications.
RESUMEN
The visible-light-driven WO3/BiOBr heterojunction was for the first time determined for its photocatalytic activity toward oxidative coupling of amines at room temperature using molecular oxygen as a green oxidant. The WO3/BiOBr heterojunction exhibits superior photocatalytic activity and photostability compared with pure BiOBr and WO3 due to an increased oxygen vacancy concentration, an effective separation of photogenerated electron-hole pairs and an efficient interfacial charge transfer. Additionally, the WO3/BiOBr also shows 2.3 and 41.1 times higher activity than that of TiO2 P25 and BiVO4 Alfa Aesar, respectively. Determination of energy band line-up indicates that the WO3/BiOBr is a type II-heterojunction where electron-hole pairs are efficiently separated. Mechanistic studies based on radical quenching experiment, EPR trapping study and Hammett plot reveal that the main reaction pathway is the electron transfer route mediated by superoxide radical. A possible surface reaction mechanism, the insightful information on the structure-activity relationship and the involvement of reactive oxygen species elucidated in this work lay an important background for the material design and encourage a further development of highly efficient photocatalysts toward organic fine chemical syntheses.
RESUMEN
The present study reported the preparation of BiVO4 by co-precipitation method. The as-prepared BiVO4 photocatalyst were deposited on rGO sheets to form BiVO4/rGO via the hydrothermal method. The crystalline structure, morphological, optical properties, and surface properties of the synthesized pure BiVO4 compared to BiVO4/rGO composite were studied using X-ray diffraction (XRD), scanning electronmicroscopy (SEM), photoluminescence (PL) spectrophotoscopy, UV-vis spectrophotometer with an integrating sphere, and N2 adsorption-desorption isotherm based on BET theory. The photocatalytic activity of the prepared samples were evaluated by the degradation of MB dye in aqueous medium under visible light irradiation. The result showed that the BiVO4/rGO composite exhibited greater photocatalytic efficiency compared to pure BiVO4 with the photocatalytic degradation efficiency remains stable up to fifth cycle. The improved activity of the BiVO4/rGO composite might be attributed to the high surface area available to adsorb more MB molecules, and efficient charge separation of BiVO4 through π electron on the rGO structure. According to experimental results, the possible photocatalytic mechanism of the BiVO4/rGO composite were determined and the active species hydroxyl radical were reported. Based on photocatalytic activity inhibition in the presence of both h+ (VB) and O2â¢- (CB) scavengers over the BiVO4 photocatalyst, it can be proposed that the hydroxyl radical generated during the photocatalytic degradation mechanism is mainly responsible by the main active species of h+ and O2â¢- at VB and CB positions, respectively.
RESUMEN
The silicon dioxide (SiO2)-coated bismuth vanadate (BiVO4) composites as visible-driven-photocatalysts were successfully synthesized by the co-precipitation method. The effects of SiO2 coating on the structure, optical property, morphology and surface properties of the composites were investigated by X-ray diffraction (XRD), UV-visible diffuse reflectance spectroscopy (DRS), transmission electron microscopy (TEM) and Brunauer-Emmette-Teller (BET) measurements. The photocatalytic activity of monoclinic BiVO4 and BiVO4/SiO2 composites were evaluated according to the degradation of methylene blue (MB) dye aqueous solution under visible light irradiation. The SiO2-coated BiVO4 composites showed the enhancing photocatalytic activity approximately threefold in comparison with the single phase BiVO4.
RESUMEN
The properties and photocatalytic performance of anatase nanoparticles of pure TiO2 and a core-shell structure of TiO2 on calcined vetiver grass leaves have been compared. Samples were fabricated by sol-gel and heating at 450 °C for 5h.The comparison was based on data for X-ray diffraction(XRD), UV-Vis spectrophotometry, photoluminescence, transmission electron microscopy, specific surface area measurement, pore volume assessment, and methylene blue degradation testing. The results showed that the pure TiO2 consisted of agglomerated equiaxed nanoparticles of individual grain sizes in the range 10-20 nm. In contrast, the TiO2-vetiver composite exhibited a core-shell structure consisting of a carbonaceous core and TiO2 shell of thickness 10-15nm. These features influenced the photocatalytic performance in such a way that the lower crosssectional area, greater surface area, and higher pore volume of the TiO2 shell increased the number of active sites, reduced the charge carrier diffusion distance, and reduced the recombination rate, thereby improving the photocatalytic activity. This improvement derived from morphological characteristics rather than crystallographic, semiconducting, or optical properties. The improved performance of the TiO2-vetiver core-shell was unexpected since the X-ray diffraction data showed that the crystallinity of the TiO2 was lower than that of the pure TiO2. These outcomes are attributed to the reducing effect of the carbon on the TiO2 during heating, thereby facilitating the formation of oxygen vacancies, which enhance charge separation and hence photocatalysis by TiO2.
RESUMEN
The main task of the present work is to enhance the photocatalytic degradation efficiency of methylene blue (MB) by using CeO2/sugarcane bagasse (SCB) composite catalysts. Homogeneous precipitation method was used to synthesis CeO2-SCB composite catalysts by adding SCB powder to precursor solution of Ce base-metal. The structural analytical data indicated the pure cubic fluorite structure of CeO2. Morphological images revealed the coating of CeO2 layer on high surface area of SCB core-shell. The chemical analysis presented spectrum of the Ce 3d in CeO2/SCB sample existed in the form of the Ce3+ and Ce4+ mixed- valence states. Optical spectra showed the shift of absorption edge towards longer visible region upon supporting CeO2 with SCB. The main chemical composition of the SCB was K, Ca, and Si. Furthermore, recombination of the photogenerated electrons and holes was identified by photoluminescence techniques (PL), the data suggested inhibition of electron-hole pairs recombination by the cations from SCB loaded in CeO2/SCB composite. Photocatalytic activity of CeO2/SCB catalyst was investigated via the degradation of MB under UV-A irradiation. Experimental kinetic data followed the pseudo-first order model. CeO2 supported with SCB adsorbent had higher photocatalytic activity in dye wastewater treatment compared to the pure CeO2. The proposed mechanism explaining the high photocatalytic efficiency of CeO2/SCB was associated with high surface properties and the suppression of recombination of the photogenerated electron-hole pairs by the SCB adsorbent.