Highly Efficient Visible-Light-Induced Photocatalytic Activity of Fe-Doped TiO2 Nanoparticles

Bare TiO2 and nominal 5.0 at% Fe-doped TiO2 nanoparticles were synthesized by the modified sol-gel method. The samples were physically characterized in order to obtain the correlation between structure and photocatalytic properties by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brunauer, Emmett and Teller (BET), and UV-vis diffuse reflectance spectrophotometry (UV-vis DRS). XRD results indicated that phase structures of bare TiO2 and Fe-doped TiO2 nanoparticles were the mixture of anatase and rutile phases. The content of rutile phase in 5.0 at% Fe-doped TiO2 nanoparticles decreased . TEM images revealed that the shape of bare and 5.0 at% Fe-doped TiO2 was almost spherical and the average particle size was in the range of 10-30 nm. Specific surface areas of the samples were found as 75 and 134 m2/g for bare TiO2 and nominal 5.0 at% Fe-doped TiO2, respectively. The results from UV-vis reflectance spectra clearly indicated the shift of absorption band edge towards visible region upon doping TiO2 with iron. Photocatalytic activity of bare TiO2 and 5.0 at% Fe-doped TiO2 nanoparticles was examined by studying the mineralization of oxalic acid under visible light irradiation and the results clearly showed that Fe-doped TiO2 sample exhibited higher activity than bare TiO2

Photocatalytic Degradation of Phenol over Highly Visible-Light Active BiOI/TiO2 Nanocomposite Photocatalyst

BiOI/TiO2 nanocomposites were successfully prepared by the two-step method, co-precipitation/solvothermal method. The amount of BiOI in the composites were varied as 0, 5.0, 7.5, 10.0 and 12.5 mol%. XRD results exhibited sharp and narrow diffraction peaks of both BiOI and TiO2 in all composite samples. Morphologies of as-prepared samples consisted of spherical shapes of TiO2 and nanosheets of BiOI. Difuse Reflectance UV-visible (DR-UV-vis) spectra of composites drastically shifted into the visible range and the reduced band gap energies were observed. The composits obviously showed an enhanced phenol degradation of ca. 6 times higher than that of pure BiOI, pure TiO2 and Degussa P25. The maximum photocatalytic activity of ca. 68% was found for 10.0 mol% BiOI/TiO2 nanocomposite because of its increased visible-light-harvesting ability and its efficient electron-hole separation efficiency as observed from DR-UV-vis and PL spectra results

Bismuth-rich oxyhalide (Bi7O9I3?Bi4O5Br2) solid-solution photocatalysts for the degradation of phenolic compounds under visible light

Hypothesis: The development of solid-solution photocatalysts with tunable bandgaps and band struc- tures, which are significant factors that influence their photocatalytic properties, is crucial. Experiments: We fabricated a series of novel bismuth-rich Bi7O9I3–Bi4O5Br2 solid-solution photocatalysts with controlled I:Br molar ratios (denoted as B-IxBr1-x, x = 0.2, 0.3, 0.4, or 0.6) via a rapid, facile, and energy- efficient microwave-heating route. The photodegradations under visible-light irradiation of the phenolic compounds (4-nitrophenol (4NP), 3-nitrophenol (3NP), and bisphenol A (BPA)), and the simultaneous photodegradation of BPA and rhodamine B (RhB) in a coexisting BPA ? RhB system were investigated. Findings: The B-I0.3Br0.7 solid solution provided the highest photocatalytic activity toward 4NP degrada- tion, with degradation rates 32 and 4 times higher than those of Bi7O9I3 and Bi4O5Br2, respectively. The photodegradation efficiency of the studied phenolic compounds followed the order BPA (97.5%) > 4NP (72.8%) > 3NP (27.5%). The RhB-sensitization mechanism significantly enhanced the photodegradation efficiency of BPA. Electrochemical measurements demonstrated the efficient separation and migration of charge carriers in the B-I0.3Br0.7 solid solution, which enhanced the photocatalytic activity. The B- I0.3Br0.7 solid solution effectively activated molecular oxygen to produce ?O2 ?, which subsequently pro- duced other reactive species, including H2O2 and ?OH, as revealed by reactive-species trapping, nitroblue tetrazolium transformation, and o-tolidine oxidation experiments

Photocatalytic Degradation of Phenol Using Nb-Loaded ZnO Nanoparticles

Niobium-doped Zinc Oxide nanoparticles (Nb-doped ZnO NPs) in the range of 20 and 40 nm were synthesized by Flame Spray Pyrolysis (FSP) technique. The crystalline phase, morphology and size of the nanoparticles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and UV-vis spectroscopy. The specific surface area of the nanoparticles was measured by nitrogen adsorption (BET analysis). The pure ZnO and Nb-doped ZnO NPs were found to have the clear spherical, hexagonal and rod-like morphologies. To the best of our knowledge, the application of Nb-doped ZnO NPs as a photocatalyst has not been reported yet. In this study, the photocatalytic activities of pure ZnO and Nb-doped ZnO NPs were determined by studying the mineralization of phenol under UV light illumination. The results indicated that all Nb-doped ZnO NPs have better photocatalytic activity than the pure ZnO nanoparticles. It was found that, 0.50 mol% Nb-doped ZnO NPs exhibited the fastest response to the degradation of phenol

Synthesis and Characterization of the Novel BiVO4/CeO2 Nanocomposites

Novel BiVO4/CeO2 nanocomposites were synthesized by the hydrothermal method combined with the homogeneous precipitation method. The mole ratios of BiVO4:CeO2 were 0.4:0.6, 0.5:0.5, and 0.6:0.4. The obtained BiVO4/CeO2 nanocomposites were characterized by X-ray diffraction (XRD) for phase composition and crystallinity. Particle sizes, morphology and elemental composition of BiVO4/CeO2 composites were examined by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive X-ray spectroscopy (EDS). 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 composite catalysts. The results indicated that BiVO4/CeO2 samples retained monoclinic scheelite and fluorite structures. The morphologies of nanocomposite samples consisted of rod-like, plate-like and spheroidal shapes. Specific surface area (SSABET) of the novel synthesized catalysts drastically increased from 38 - 150 m2/g whereas an average BET-equivalent particle diameter (dBET) significantly decreased from 30 - 12 nm, upon increasing the amount of CeO2 in the BiVO4/CeO2 composite. The absorption spectra of all nanocomposite samples were shifted to the visible region, suggesting the potential application of this novel composite as an active visible-light driven photocatalyst

Photocatalytic Mineralization of Organic Acids over Visible-Light-Driven Au/BiVO 4

Au/BiVO4 visible-light-driven photocatalysts were synthesized by coprecipitation method in the presence of sodium dodecyl benzene sulfonate (SDBS) as a dispersant. Physical characterization of the obtained materials was carried out by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), UV-Vis diffuse reflectance spectroscopy (DRS) and Brunauer, and Emmett and Teller (BET) specific surface area measurement. Photocatalytic performances of the as-prepared Au/BiVO4 have also been evaluated via mineralizations of oxalic acid and malonic acid under visible light irradiation. XRD and SEM results indicated that Au/BiVO4 photocatalysts were of almost spherical particles with scheelite-monoclinic phase. Photocatalytic results showed that all Au/BiVO4 samples exhibited higher oxalic acid mineralization rate than that of pure BiVO4, probably due to a decrease of BiVO4 band gap energy and the presence of surface plasmon absorption upon loading BiVO4 with Au as evidenced from UV-Vis DRS results. The nominal Au loading amount of 0.25 mol% provided the highest pseudo-first-order rate constant of 0.0487 min−1 and 0.0082 min−1 for degradations of oxalic acid (C2) and malonic acid (C3), respectively. By considering structures of the two acids, lower pseudo-first-order rate constantly obtained in the case of malonic acid degradation was likely due to an increased complexity of the degradation mechanism of the longer chain acid

Photocatalytic activity of CuInS2 nanoparticles synthesized via a simple and rapid microwave heating process

In this research, visible–light photocatalytic activities of CuInS2 nanoparticles for degradation of three organic dyes (rhodamine B; RhB, methylene blue; MB, and methyl orange; MO) were investigated. The CuInS2 nanoparticles were synthesized by a simple and rapid microwave heating process using sodium sulfide as a sulfur source and then characterized by x–ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), Brunauer–Emmett–Teller (BET), and UV–vis diffuse reflectance spectroscopy (UV–vis DRS) techniques. The synthesized CuInS2 nanoparticles exhibited excellent photocatalytic degradation activity to the cationic dyes (RhB and MB) when compared with that of anionic dye (MO). Zeta potential of the CuInS2 photocatalyst was measured to elucidate the adsorption ability toward dye molecules. A possible photocatalytic degradation mechanism was proposed based on active species quenching experiments and Mott–Schottky analysis

Enhanced photoactivity and selectivity over BiOI-decorated Bi2WO6 microflower for selective oxidation of benzylamine: Role of BiOI and mechanism

The importance of developing effective and selective photocatalytic materials to realize efficient renewable energy-based organic synthetic processes, such as selective oxidation of benzylamines and its derivatives to the corresponding imines has become more apparent in recent years. Here we present the first reported BiOI/Bi2WO6 (BI/BW) microflower heterostructure as a visible-light-driven photocatalyst for such reactions. By decorating the hydrothermally prepared BW with BI via successive ionic layer adsorption and reaction (SILAR) method, benzylamine conversion is improved from 68 % to 92 % as compared to undecorated. Furthermore, selectivity to desired imine product is substantially increased from 59 % to 95 %. These outstanding performances are attributed to enhanced electron-hole separation and transfer efficiency as well as a greater preference for adsorption of benzylamine compared to the imine products and extended visible-light absorption range inherited from BI component as supported by competitive adsorption studies, ultraviolet–visible diffuse reflectance spectroscopy, and photoelectrochemical experiments. Possible mechanisms, band energy diagram, and decisive roles of O2−[rad] and h+ in the selective transformation of benzylamine were proposed based on Mott-Schottky, scavenging, and electron paramagnetic resonance radical trapping experiments. This work highlights a simple approach for improving photocatalytic activity and selectivity which are highly desirable in renewable energy-based chemical synthetic processes

Visible Light-Driven BiOI/ZnO Photocatalyst Films and Its Photodegradation of Methomyl Insecticide

Bismuth oxyiodide/zinc oxide (BiOI/ZnO) composite photocatalyst films were successfully prepared by a simple low temperature co-precipitation method coupled with a reflux procedure. Mole ratios of BiOI and ZnO were varied from 0, 0.125, 0.25 and 0.50 mol% while X-ray diffraction patterns confirmed characteristic peaks of BiOI and ZnO in all composite samples. Optimal photocatalytic efficiency of methomyl photodegradation under visible light irradiation was recorded for 0.25 mol% BiOI/ZnO photocatalyst at 58%. Increase in BiOI content resulted in higher photocatalytic activity than for pure ZnO and commercial ZnO. Optimal heterojunction content at 0.25 mol% BiOI/ZnO was recorded between hexagonal wurtzite ZnO and tetragonal BiOI, with high crystalline particles leading to enhanced specific surface light absorption capacity in the visible region. Based on these good characterization results for interfacial surface and X-ray Photoelectron Spectroscopy (XPS), the combination of both semiconductors generated more electrons, resulting in enhanced photocatalytic performance of methomyl degradation under visible light irradiation

MoO₃ Catalysed Hydrogenation of Nitrobenzene to Aniline at Near Room Temperature

MoO3 with orthorhombic structure (α-MoO3) was evaluated for its catalytic performance in the hydrazine-assisted transfer hydrogenation of nitrobenzene to aniline at near room temperature. The conversion of nitrobenzene, ca. 88.6% was obtained after 4 h reaction with >99% of selectivity to aniline. The activation energy from the Arrhenius plot was ca. 120.6 kJ/mol. In this system, hydrazine (N2H4) did not only act as a hydrogen donor but also as a reducing agent to generate an active catalytic phase as supported by the existence of an induction period at the early stages of the reaction. XRD and XPS characterisations of the hydrazine treated catalyst revealed the phase transformation from α-MoO3 to (NH4)0.23H0.08MoO3 containing Mo5+ species, a possible adsorption site for hydrazine decomposition to produce active hydrogen species for the transfer hydrogenation of nitrobenzene. Based on the Hammett plot, an anionic intermediate was indicated to be involved in the rate-determining step