Modern Research in Catalysis
ISSN / EISSN : 2168-4480 / 2168-4499
Published by: Scientific Research Publishing, Inc. (10.4236)
Total articles ≅ 103
Latest articles in this journal
Modern Research in Catalysis, Volume 10, pp 1-14; doi:10.4236/mrc.2021.101001
Au-TiO2 catalysts were used in the photocatalytic degradation of the methylene blue dye (MB). The synthesis of titanium oxide (TiO2) was carried out by sol-gel method. Subsequently, particles of Au were deposited on the surface of the semiconductor by photo-deposition, thus modifying the surface of the semiconductor. For the characterization of the catalyst obtained, the techniques of X-ray Diffraction (DRX), Scanning Electron Microscopy (SEM), Spectroscopy with Diffuse Reflectance (DR) and Surface Area by the BET (Brunauer, Emmett y Teller) were used. The solid obtained was tested experimentally as a catalyst in the photocatalytic degradation of a solution of MB. The data obtained were analyzed by UV-vis Spectroscopy and Total Organic Carbon (TOC) and the results indicated conversions were greater than 80%. The intermediate products were evaluated by mass coupled gas chromatography (GC-MS) and the MB decomposition route was by hydroxylation, obtaining aromatic intermediates, esters and products of the chemical degradation of the molecule.
Modern Research in Catalysis, Volume 10, pp 56-72; doi:10.4236/mrc.2021.102004
A novel Fe-Pd bifunctional catalyst supported on mesh-type γ-Al2O3/Al was prepared and applied in the degradation of Rhodamine B (RhB). The monolithic mesh-type Fe-Pd/γ-Al2O3/Al bifunctional catalyst could be separated from the solution directly and could synthesize H2O2 in situ. The characterization results showed that Fe could improve the dispersion of Pd0, and the electronic interactions between Pd and Fe could increase the Pd0 contents on the catalyst, which increased the productivity of H2O2. Furthermore, DFT calculations proved that the addition of Fe could inhibit the dissociation of O2 and promote the nondissociative hydrogenation of O2 on the surface of Fe-Pd/γ-Al2O3/Al, which resulted in the increasement of H2O2 selectivity. Finally, the in-situ synthesized H2O2 by Pd was furtherly decomposed in situ by Fe to generateOH radicals to degrade organic pollutants. Therefore, Fe-Pd/ γ-Al2O3/Al catalysts exhibited excellent catalytic activity in the in-situ synthesis of H2O2 and the degradation of RhB due to the synergistic effects between Pd and Fe on the catalyst. It provided a new idea for the design of bifunctional electro-Fenton catalysts. Ten cycles of experiments showed that the catalytic activity of Fe-Pd/γ-Al2O3/Al catalyst could be maintained for a long time.
Modern Research in Catalysis, Volume 10, pp 73-91; doi:10.4236/mrc.2021.103005
This work proposes the synthesis of the 5%wt Ru on MWCNT catalyst and the influence of feed rate and testing variables for low-temperature oxidation affecting the CO2 yield. Morphology and incorporation of the nanoparticles in carbon nanotubes were investigated by specific surface area (BET method); thermogravimetric analyses (TGA); X-ray diffraction; Raman spectroscopy, transmission electron microscopy (TEM) and XPS. The conversions of CO and O2 were mostly 100% in groups C1 and C2 (temperature between 200 and 500°C with low WHSV). In order to assess the effect of mass on catalytic activity, condition C3 was tested at even lower temperatures. In the tested catalyst, high activity (100% CO and O2 conversion) was observed, keeping it active under reaction conditions, suggesting oxi-reduction of the RuO2 at surface without affecting the MWCNT but Lewis acid influencing the CO2 yield.
Modern Research in Catalysis, Volume 10, pp 36-55; doi:10.4236/mrc.2021.102003
In this work, hierarchical BiOBr1−xIx/BiOBr heterojunction photocatalyst with a microsphere morphology was synthesized by a facile solvothermal process. It demonstrated that the local structure of the photocatalysts was highly distorted due to the substitution of bromide ions by iodine ions. The photocatalytic properties were evaluated by the photodecomposition of aqueous phenol solution under visible-light irradiation. The results indicated that all the composite photocatalysts exhibited high photocatalytic activity. In particularly, the BiOBr1−xIx/BiOBr (x = 0.25) sample exhibited over 92% degradation efficiency of phenol within 150 min, which is 24.6 and 3.08 fold enhancement in the photocatalytic activity over the pure phased BiOBr and BiOI, respectively. Moreover, this excellent photocatalytic property can be expanded to other colorless organic contaminants, verifying the common applicability of BiOBr1−xIx/BiOBr (x = 0.25) as an excellent visible-light photocatalyst for organics decomposition. The significant improvement in the photocatalytic activity can be explained by the high efficiency of charge separation due to the enhancement in the internal electric fields and band match that comes from the local structure distortion. This work provides valuable information for the design of highly active photocatalysts toward the environmental remediation.
Modern Research in Catalysis, Volume 10, pp 15-35; doi:10.4236/mrc.2021.102002
CdS/NiS nanocomposites were synthesized by electrochemical method. Ni and Cd is one of the important II-VI semiconducting materials with a direct band gap of 3.26 eV which finds applications in electrical conductivity and photo-catalysis. The synthesized nanocomposites were characterized by BET, UV-VIS, XRD, FE-SEM (EDAX) techniques. X-Ray diffraction (XRD) reveals crystallite size to be 23.22 nm which was calculated using Williamson-Hall (W-H) plot method. The energy of the band gap for CdS/NiS could be thus estimated to be 3.26 eV. The photocatalytic activity of the sample was evaluated by the degradation of textile dye methylene Blue (MB) in aqueous solutions under UV radiation. Hydrogen energy is regarded as a promising alternative in terms of energy conversion and storage. Hydrogen Evolution Reaction (HER) was carried out in both visible light and UV light by using Hydrazine (N2H4H2O) in the presence of CdS/NiS nanocomposite. The synthesized photocatalyst shows applicable performance for kinetics of Hydrogen Evolution Reaction (HER) in Visible light and UV light. The decomposition of hydrazine (N2H4H2O) proceeded rapidly to generate free hydrogen rich gas through OH radical contact with CdS/NiS nanocomposite at room temperature. The rate of HER is limited by either proton adsorption onto an active site or evolution of formed hydrogen from the surface. A high Tafel slope is indicative of proton adsorption as the rate limiting step, while a lower Tafel slope (20 - 45 mV) indicates that the evolution of molecules hydrogen from the catalyst is rate limiting. In the present case the Tafel slopes for visible light 23.5 mV and 42.5 mV for UV light. Blank experiments show poor activity for HER i.e. 10.1 - 13.5 mV.
Modern Research in Catalysis, Volume 09, pp 47-61; doi:10.4236/mrc.2020.94004
This work aimed to synthesis a novel material that would be able to efficiently remove both organic and microbiological pollutants from wastewater. Through the hydrothermal process, we first doped titanium dioxide, a semiconductor possessing excellent photocatalytic properties with silver nanoparticles having good antibacterial properties. The obtained material was then associated with clay known for its good adsorbent properties to form [AgTiO2]:[clay] type nanocomposites. The different mass composition of [AgTiO2]:[clay] considered in this work were 1:1; 1:0.5; 1:0.1; 1:0.05 and 1:0.01. The prepared nanocomposites were characterized by means of XRD, FTIR and SEM techniques. Results revealed the presence of TiO2 anatase and Ag on the surface of the clay mainly composed of kaolinite and quartz. The photocatalytic activities of the nanocomposites were tested in the presence of synthetic Orange II (25 mg/L) wastewater under visible light irradiation. The experiments demonstrated that organic pollutants were effectively photodegraded when the proportion of clay in the mixture (AgTiO2)-(Clay) was inferior or equaled to 50%. The use of commercial TiO2, for comparison purpose, showed a lower degradation efficiency of the Orange II solution (η 2]:[clay] were also assessed in the presence of two types of bacteria E. coli (Gram negative) and S. aureus (Gram positive). The antibacterial activities of the nanocomposites were characterized with and without UV irradiation. In dark conditions, the antibacterial activities of nanocomposites (AgTiO2)-(Clay) against S. aureus gradually increased with increasing the clay amount. Under visible light irradiation, the nanocomposites showed a significant antimicrobial activity against E. coli and S. aureus.
Modern Research in Catalysis, Volume 09, pp 35-46; doi:10.4236/mrc.2020.93003
The aim of this study was to develop a method to prepare WO3-TiO2 film which has high anticorrosion property when it was coated on type 304 stainless steel. A series of WO3-modified TiO2 sols were synthesized by peroxo-sol gel method using TiCl4 and Na2WO4 as the starting materials. TiCl4 was converted to Ti(OH)4 gel. H2O2 and Na2WO4 were added in Ti(OH)4 solution and heated at 95°C. The WO3-TiO2 sol was transparent, in neutral (pH~7) solution, stable suspension without surfactant, nano-crystallite and no annealing is needed after coating, and very stable for 2 years in stock. WO3-TiO2 sol was formed with anatase crystalline structure. These sols were characterized by XRD, TEM, and XPS. The sol was used to coat on stainless steel 304 by dip-coating. The WO3-TiO2 was anatase in structure as characterized by X-ray diffraction. There were no WO3 XRD peaks in the WO3-TiO2 sols, indicating that WO3 particles were very small, possibly incorporating into TiO2 structure, providing the amount of WO3 was very small. The TiO2 particles were rhombus shape. WO3-TiO2 had smaller size area than pure TiO2. The SEM results showed that the film coated on the glass substrate was very uniform. All films were nonporous and dense films. Its hardness reached 2 H after drying at 100°C, and reached 5 H after annealing at 400°C. The WO3-TiO2 film coated on 304 stainless steel had better anticorrosion capability than the unmodified TiO2 film under UV light illumination. The optimum weight ratio of TiO2: WO3 was 100:4.
Modern Research in Catalysis, Volume 09, pp 21-34; doi:10.4236/mrc.2020.92002
Ni promoted structured plate-type Pt/Nix/a-AlOOH catalysts were developed to enhance the amount of hydroxyl group, therefore improving the catalytic activities for formaldehyde oxidation at room temperature. The analyzation results by XRD and HRTEM indicate that two kinds of materials, AlOOH and NiOOH, are detected on the surface of Pt/Nix/a-AlOOH. It can be seen from the result of TG that the hydroxyl group on the catalyst surface increased after Ni was loaded. Furtherly, XPS results show that the percentage of hydroxyl groups which can effectively absorb formaldehyde increases from 36.4% to 72.8% by doping Ni. In addition, the content of Pt0 increased from 27.5% to 45%. The results indicate that optimized Pt1.15/Ni3.1/a-AlOOH has the best catalytic activity with the CO2 conversion is 88% at 25°C and 100% at 40°C, while CO2 conversion over Pt1.2/a-AlOOH is 56% at 25°C and 100% at 100°C respectively. Hence, the Ni promoted plate-type Pt/a-AlOOH possesses high efficiency and it provides a new idea for catalyst design of formaldehyde oxidation.
Modern Research in Catalysis, Volume 09, pp 1-19; doi:10.4236/mrc.2020.91001
A series of Ag/TiO2 with various Ag contents were prepared by photoreduction method. Commercial TiO2 from Evonik-Degussa was used as the catalyst. Ag was used as the cocatalyst. This facial synthesis method is cheap and easy. TiO2 was suspended in water with various concentrations of silver nitrate. The solution was illuminated by UV light for 36 h. Ag would deposit on the surface of TiO2. This method can deposit all Ag cation in the starting material on TiO2 after 36 h irradiation by UV light. X-ray diffraction, high resolution-TEM, and X-ray photoelectron spectroscopy were used to characterize the surface, morphology and chemical composition of the catalysts. Photocatalytic degradation of methylene blue in water on these catalysts was carried out under UV and visible light irradiation, respectively. The methylene blue concentration in water was measured by a UV-vis spectrophotometer. The results showed that the bulk structure of TiO2 did not change and some of Ag was incorporated into the surface of TiO2 lattice. The change in the electronic state of Ti on surface is attributed to the replacement of titanium atoms by silver atoms on the TiO2 surface structure which induced visible light response and enhanced the photocatalytic activity. 1 wt% Ag is the optimum loading to have high activity.
Modern Research in Catalysis, Volume 08, pp 1-9; doi:10.4236/mrc.2019.81001