DR UV Vis Spectroscopy Research Articles

Fe-ZSM-5 outperforms Al-ZSM-5 in paraffin cracking by increasing the olefinicity of C3-C4 products

Iron-modified Al-ZSM-5 increases selectivity to propene, a key petrochemical resulting from fluid catalytic cracking (FCC). However, the type and role of active iron species remain unclear, hindering efforts to streamline the design of selective FCC additives. Here, we investigated Al-free Fe-ZSM-5 catalysts containing iron species in the form of framework Fe3+, extra-framework Fe3+, oxidic clusters, and oxide micro aggregates in n-octane cracking (FCC model) to assess their effect on catalytic cracking. DR-UV–Vis spectroscopy, 57Fe Mössbauer Spectroscopy, FTIR studies of pyridine adsorption, and n-octane cracking tests at 500 °C revealed that framework-associated coordinatively unsaturated Fe3+ species, which induce strong Lewis acidity, are responsible for paraffin cracking initiation, whereas bulk iron oxides on the zeolite surface are inactive. In comparison with Al-ZSM-5, Fe-ZSM-5 increases the olefinicity of the valuable C3-C4 fractions (selectivity to propene and butenes) and promotes aromatization reactions due to the lower relative strength of Fe-induced Brønsted acid sites and dehydrogenation properties. As shown by our 57Fe Mössbauer study (performed at −269 °C) of the catalyst in calcined, spent, and regenerated states, Fe-ZSM-5 deactivation is associated with the loss of tetrahedrally coordinated Fe3+ species. Therefore, tuning Fe-ZSM-5 C3-C4 selective FCC additives requires stabilizing framework Brønsted and framework-associated Lewis acid sites while decreasing the concentration of iron oxide species. Ultimately, these findings may enable us to meet the demand for propene derived from FCC cracking, which is expected to grow in the foreseeable future.

Post-Synthetically Treated ERI and SSZ-13 Zeolites Modified with Copper as Catalysts for NH3-SCR-DeNOx

ERI and SSZ-13 were subjected to post-synthetic treatments (depending on the zeolite topology) to create micro-/mesoporous materials. The results in terms of NH3-SCR-DeNOx show that the applied treatments improved the catalytic activity of the Cu-containing ERI-based materials; however, the NO conversion did not vary for the different materials treated with NaOH or NaOH/HNO3. For the micro-/mesoporous Cu-containing SSZ-13, a lower NO conversion in NH3-SCR-DeNOx was observed. Thus, our findings challenge the current paradigm of enhanced activity of micro-/mesoporous catalysts in NH3-SCR-DeNOx. The modification of the supports results in the presence of different amounts and kinds of copper species (especially isolated Cu2+ and aggregated Cu species) in the case of ERI- and SSZ-13-based samples. The present copper species further differentiate the formation of reactive reaction intermediates. Our studies show that besides the μ-η2,η2-peroxo dicopper(II) complexes (verified by in situ DR UV-Vis spectroscopy), copper nitrates (evidenced by in situ FT-IR spectroscopy) also act as reactive intermediates in these catalytic systems.

Co-Zn nanoparticles on N-doped graphene nanocomposites as bifunctional catalysts for non-enzymatic electrochemical sensor and organic dye degradation

Detection of biomolecules by advanced sensing systems and organic pollutant removal is of immense interest in biomedical and environmental remediation sectors. In this regard, effective glucose detection is dynamic in rapid-diagnosis of related diseases and in addition, removal of organic dyes by suitable adsorbent materials is vital for water treatment. The present work involves the facile fabrication of CoZn-N doped graphene nanocomposites and employed in glucose sensors and dye removal. The synthesized materials were characterized to evaluate the structural, morphological, elemental and surface characterizations such as, X-ray diffraction (XRD), Fourier transform infrared (FTIR), scanning DR-UV–vis–spectroscopy, electron microscopy (SEM), energy dispersive X-ray analysis (EDAX), transmission electron microscopy (TEM) techniques, X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. SEM and TEM images revealed the Co-Zn nano particles (NPs) with respective morphologies within the N doped graphene structure. Electrochemical examinations of CoZn-N doped graphene nanocomposites/GCE sensor demonstrated superior sensitivity for the detection of commercial glucose in NaOH. Moreover, CoZnNG nanocatalyst has been investigated for the dye removal of crystal violet (CV), Rhodamine B (RB), methylene blue (MB) and congo red (CR) in the presence of H2O2. CoZnNG catalyst exhibited a maximum efficiency of 96 % over CV dye degradation in 30 min which is comparatively higher than the removal of MB, CR and RB dyes with 36 %, 41 %, 38 % for 120, 60 and 100 min, respectively. The CoZn-N doped graphene nanocomposites exhibited regeneration, reproducibility, and stability toward dye removal. Such multi-component hybrid N doped graphene could be efficacious for real-time non-enzymatic electrochemical sensor and pollutant removal applications.

Probing the effect of the Si/Al ratio in Cu-CHA zeolite catalysts on SO2 exposure: in situ DR UV-vis spectroscopy and deactivation measurements

UV-vis shows the effect of SO2 on [CuII2(NH3)4O2]2+ complexes in Cu-CHA catalysts with different Si/Al ratios. The amount of [CuII2(NH3)4O2]2+ correlates with the activity in NH3-SCR and sulfur uptake, but not with deactivation.

Fine-tuning mesoporous silica properties by a dual-template ratio as TiO2 support for dye photodegradation booster

Titanium dioxide (TiO2) has been integrated into the surface of mesoporous silica (SMG) synthesized via the hydrothermal approach and a dual template CTAB-Gelatin. XRD, nitrogen adsorption, FTIR, SEM-EDX, and UV–Vis DR spectroscopy were performed to evaluate a 1 wt% TiO2/SMG material. After titania incorporation, the addition of gelatin during the synthesis of SMG increases the pore volume to 0.76 cc/g. The expansion of the silica pores is caused by the development of TiO2 crystal grains on the mesoporous silica-gelatin. An increase in the gelatin-CTAB to mesoporous silica weight ratio modifies the surface area, pore size, and particle size without compromising the meso-structure. In this research, the TiO2/SMG composite demonstrated much greater photodegradability for methylene blue (MB) than the TiO2/mesoporous silica sample without gelatin. The experimental results indicate that the photocatalytic activity of methylene blue from SMG titania/silica samples is reliant on the adsorption ability of the composite and the photocatalytic activity of titania, with optimal activity from samples with the highest surface area and pore volume, which directly increase the Ti: Si ratio and decrease the photodegradability of the composite when the ratio is too high or too low.

Performance evaluation and optimization of ZnO-PVP nanoparticles for photocatalytic wastewater treatment: Interactions between UV light intensity and nanoparticles dosage

In recent decades, the application of nanoparticles for environmental remediation purposes has received great attention due to their promising removal efficiency. In this research, we evaluated photocatalytic performance of synthesized zinc oxide-polyvinylpyrrolidone (ZnO-PVP) as modified ZnO nanoparticles for chemical oxygen demand (COD) reduction and phosphate removal from municipal wastewater. Furthermore, the synergistic effect of UV light intensity and ZnO-PVP dosage on photocatalytic treatment was investigated. To do this, after characterization of the synthesized ZnO-PVP nanoparticles by SEM, EDX, FTIR, XRD, UV–Vis DR spectroscopy and BET analysis, the effect of ZnO-PVP and single ZnO treatment on COD reduction and phosphate removal was compared using different dosages of nanoparticles (1, 1.5, 2 and 2,5 g/L). The interaction effects of UV light intensity and nanoparticles dosage were investigated by performing 12 batch experiments. The results proved that using ZnO-PVP could improve the photocatalytic treatment of COD (from 63% to 83%) and phosphate (from 68% to 87%), in comparison with single ZnO. It has been observed that UV light intensity directly affects ZnO-PVP photocatalytic treatments performance. Maximum removal efficiencies of 95% and 97% were achieved for COD and phosphate, respectively, under optimal condition of ZnO-PVP dosage of 1.5 g/L and UV intensity of 2293 mW/cm2. This research suggests that under the optimal condition, ZnO-PVP nanoparticles can be used as a promising approach for COD reduction and phosphate removal from wastewater.

The effect of vanadium addition in Ni1-xVxFe2O4 nano photocatalysts on remazol golden yellow degradation under visible light irradiation

Photocatalysis is a promising solution for the degradation of dyes since this substance harms the environment. In addition, this process is environmentally friendly, especially while using low energy through visible light irradiation. In this study, Ni1-xVxFe2O4 nano-photocatalyst has been prepared using the sol-gel method. After freeze-drying and calcination processes, the sample was characterised using the techniques of x-ray diffraction (XRD), FTIR, UV–vis DR spectroscopy, TEM, and Particle Size Analyser (PSA). The XRD results indicated that a majority of the crystalline phase in this material prepared is NiFe2O4 spinel. Then, the grain size of this spinel is in the range of 20–32 nm. UV–vis DR spectroscopy analysis indicated that the bandgap energy of spinel Ni1-xVxFe2O4 (where x = 0.1–0.5) is 1.6, 1.8, and 2.0 eV, respectively. FTIR analysis explained that catalyst functions as the photocatalyst, and maintains the structure after the reaction. Furthermore, results of dye photodegradation indicated that Ni1-x V x Fe2O4 nanocatalysts are all active and able to degrade remazol golden yellow (RGY) by more than 30% conversion under the visible light irradiation. In two stages of experiments to degrade RGY, Ni0.5V0.5Fe2O4 nanocatalyst has the best activity with more than 65% conversion. However, based on the linearity correlation in determining the order reaction, it is clear that the rate is a pseudo-first-order reaction and the best rate constant for reaction below 80 min, k = 0.0029 min−1 for Ni0.7V0.3Fe2O4 photocatalyst.

Noble Metals Deposited LaMnO3 Nanocomposites for Photocatalytic H2 Production.

Due to the growing demand for hydrogen, the photocatalytic hydrogen production from alcohols present an intriguing prospect as a potential source of low-cost renewable energy. The noble metals (Ag, Au, Pd and Pt) deposited LaMnO3 nanocomposites were synthesized by a non-conventional green bio-reduction method using aqueous lemon peel extract, which acts as both reducing and capping agent. The successful deposition of the noble metals on the surface of LaMnO3 was verified by using powder XRD, FTIR, TEM, N2-physisorption, DR UV-vis spectroscopy, and XPS techniques. The photocatalytic activity of the synthesized nanocomposites was tested for photocatalytic H2 production under visible light irradiation. Different photocatalytic reaction parameters such as reaction time, pH, catalyst mass and reaction temperature were investigated to optimize the reaction conditions for synthesized nanocomposites. Among the synthesized noble metal deposited LaMnO3 nanocomposites, the Pt-LaMnO3 nanocomposite offered superior activity for H2 production. The enhanced photocatalytic activity of the Pt-LaMnO3 was found as a result from low bandgap energy, high photoelectrons generation and enhanced charge separation due to deposition of Pt nanoparticles. The effective noble metal deposition delivers a new route for the development of plasmonic noble metal-LaMnO3 nanocomposites for photocatalytic reforming of aqueous methanol to hydrogen.

Insights into catalytic reduction of dyes catalyzed by nanocomposite beads Alginate@Fe3O4: Experimental and DFT study on the mechanism of reduction

In the present work, a facile pathway was developed to prepare magnetic alginate nanocomposite beads (M@AN). The prepared nanocomposite beads were evaluated as a catalyst for the degradation of methylene blue (MB) and orange G (OG) dyes in a simple and binary system under the presence of a reducing agent NaBH4. The in-situ formed magnetic nanoparticles (Fe3O4-NPs) were identified by visual observance, X-ray diffraction (XRD), UV–Vis DR Spectroscopy (UV–vis DR), Fourier transform infrared (FTIR) spectroscopy and energy dispersive x-ray (EDS). The obtained results revealed the formation of dispersed Fe3O4-NPs inside the beads linked with −COO groups of alginate biopolymer by a bidentate bridging coordination. Owing the presence and well-dispersed Fe3O4 nanoparticles in M@AN surface. The prepared catalyst was more efficient with the cationic MB dye in the simple and binary system. In the simple system, the rate constant was 0.0034 s−1 and 7.416 10−4 s−1 for MB and OG dye, respectively, whereas in the binary system the rate constant was 0.0012 s−1 and 5.096 10−4 s−1 for MB and OG dye, respectively. To have deep insight into the reduction mechanism of MB dye onto M@AN, the density functional theory (DFT) method was used. The results showed that the NaBH4 and MB reagents are firstly diffused onto the surface of the nanocatalyst via hydrogen banding, then, the reduction reaction was carried out by a nucleophilic attack of borohydride ion by hydrogenation on the double bond between carbon and nitrogen in –NC– group of MB which thereafter transformed into –NH–CH– bond. The theoretical results show good agreement with the experimental data, in which the calculated UV–visible spectrum of Leuco–MB product using DFT method shows an electronic transition at 300 nm which is a close value to the experimental.

Removal of volatile dimethyl sulfoxide from wastewater using hydrogen peroxide catalyzed by supported molybdenum oxide

Due to its excellent solubility for many chemicals, DMSO is widely used as solvents in industries. The biodegradation of DMSO is pretty slow and gives out noxious and volatile compounds like dimethylsulfide, methyl mercaptan, and hydrogen sulfide. Therefore, a green and efficient DMSO removal process is needed. In this work, supported molybdenum oxide catalysts were prepared and were characterized with powder XRD, SEM, TEM, Raman, DR-UV–vis spectroscopy and XPS. These catalysts are efficiently active for the catalytic oxidation of DMSO in wastewater using green oxidant, H2O2. The degradation product of DMSO is DMSO2 which is an environmentally friendly and biodegradable compound and can be further removed by biological processes without forming hazardous sulfides. Fumed SiO2 is the best support for MoO3 and the catalytic activity increases with the increase of the MoO3 loading. DMSO (179 mmol/L) is completely removed after a 2-hour reaction at 50 °C. EPR analyses and control experiments with radical scavengers confirm that the oxidative degradation of DMSO is not a radical reaction. Thus, a non-radical oxidation mechanism is proposed for the degradation of DMSO. The kinetic study on the 30 wt% MoO3/SiO2 catalyst confirms that the catalytic oxidation reaction of DMSO is a pseudo-first-order reaction with an apparent activation energy of 68.5 kJ/mol. When the initial concentration of DMSO is further increased to 264 or 344 mmol/L, the MoO3/SiO2 catalyst can still remove it within 2 h. In conclusion, this catalyst is a promising candidate for treating industrial wastewater containing DMSO.

Efficient treatment of organic pollutants by boron doped TiO2 photocatalysts under visible light radiation

As one of the most widely used photocatalysts, TiO2 suffers from the limited application with respect to harvesting solar energy for the environmental remediation. One way to perform the TiO2 modification is by doping, through which the doped TiO2 would be able to absorb the visible light from the solar illumination as a visible reactive catalyst. The objective of this work is to synthesize boron-doped TiO2 (B@TiO2) photocatalysts using a method called sol–gel. The as-synthesized catalysts were characterized using DR UV–vis spectroscopy, XRD, photoluminescence, XPS, SEM, EDS and TEM. The XRD results show that doping of boron constituent could hinder the grain crystallite growth and selectively favor the anatase phase formation and diboron trioxide phase, B2O3. The characterization works indicated an enhanced absorption edge of B@TiO2 and reduced band gap energy to enable the visible light photocatalytic activity. The lowest intensity of PL result signaled the slowest recombination rate of electron by supposedly newly created energy level by the doped boron, was achieved by 6B@TiO2. The 6B@TiO2 demonstrated the most efficient performance with greater than 93% of MB degradation, owing to the aforementioned modification of the optical and electronic properties during the optimization effort of catalyst synthesis. In this work, a less energy intensive sol–gel procedure was carried out to produce the equally efficient photocatalysts. As a conclusion, the doping mechanism has extended the absorption spectrum of TiO2 and successfully degraded the model dye within the controlled experimental conditions.

Preparation of core-shell heterojunction photocatalysts by coating CdS nanoparticles onto Bi4Ti3O12 hierarchical microspheres and their photocatalytic removal of organic pollutants and Cr(VI) ions

Herein we have assembled CdS nanoparticles onto the surface of Bi4Ti3O1 (BTO) hierarchical microspheres to construct core-shell BTO/CdS heterojunction photocatalysts. The as-prepared samples are systematically analyzed by various methods (e.g., XRD, SEM, TEM, XPS, UV–vis DR spectroscopy and FTIR spectroscopy), confirming the formation of core-shell structured BTO/CdS composites. Photocurrent response and EIS analyses demonstrate that enhanced separation of photogenerated electron-hole pairs is realized in the BTO/CdS heterojunctions. Simulated-sunlight driving photodegradation of methylene blue (MB) reveals that the optimal composite sample 20%BTO/CdS is endowed with a photocatalytic activity about 1.6 and 3.3 times higher than that of bare CdS and BTO, respectively. Moreover, the 20%BTO/CdS heterojunction photocatalyst also exhibits excellent photocatalytic elimination of methyl orange (MO)/rhodamine B (RhB)/MB mixture dyes, ciprofloxacin (CIP), sulfamethoxazole (SMX), tetrabromobisphenol A (TBBPA) and Cr(VI) ions. The enhanced photocatalytic mechanism of the BTO/CdS heterojunction photocatalysts was discussed based on a Z-scheme carrier transfer process.

Photocatalytic hydrogen production from water-methanol and -glycerol mixtures using Pd/TiO2(-WO3) catalysts and validation in a solar pilot plant

This paper is focused on the photocatalytic hydrogen production on Pd/TiO2(-WO3) catalysts from water-methanol and water-glycerol mixtures under UVA and solar irradiation. The photodeposition method for Pd was studied varying conditions such as Pd amount, catalyst concentration and methanol concentration. The catalysts were tested at lab scale under simulated solar light and UVA radiation and also at large scale (25 L) under solar energy using a pilot-scale solar Compound Parabolic Collector (CPC). The catalysts characterization was performed by means of ICP-OES, N2 adsorption–desorption isotherms, XRD, HR-TEM, XPS and DR–UV–Vis spectroscopy. Hydrogen evolution was monitored by on-line gas chromatography.From results it was found the Pd photodeposition method plays a key role to increase the hydrogen evolution, affecting parameters like the Pd amount deposited, the Pd nanoparticles size and dispersion. The highest quantum efficiency (ϕ) obtained in this study was 11.8% and 41.2% under simulated solar and UVA irradiation, respectively, using Pd(0.24 wt%)/P25 in an aqueous solution of methanol (50 vol%). In the pilot-scale solar CPC, for Pd(0.24 wt%)//P25 catalysts in 5 vol% of methanol or glycerol as sacrificial agents, the quantum yield were 2.1 and 2.2%, respectively. When the concentration of the sacrificial agents decreased to 0.37 vol%, the quantum yields were 1.3 and 2.4% for methanol and glycerol, respectively. Compared to literature, the low noble metal content of these catalysts (0.25 wt%) seems to be a competitive factor considering their high price.

P-060. adverse effects of the use of magnesium sulfate in a patient with preeclampsia

This paper is focused on the photocatalytic hydrogen production on Pd/TiO2(-WO3) catalysts from water-methanol and water-glycerol mixtures under UVA and solar irradiation. The photodeposition method for Pd was studied varying conditions such as Pd amount, catalyst concentration and methanol concentration. The catalysts were tested at lab scale under simulated solar light and UVA radiation and also at large scale (25 L) under solar energy using a pilot-scale solar Compound Parabolic Collector (CPC). The catalysts characterization was performed by means of ICP-OES, N2 adsorption–desorption isotherms, XRD, HR-TEM, XPS and DR–UV–Vis spectroscopy. Hydrogen evolution was monitored by on-line gas chromatography.From results it was found the Pd photodeposition method plays a key role to increase the hydrogen evolution, affecting parameters like the Pd amount deposited, the Pd nanoparticles size and dispersion. The highest quantum efficiency (ϕ) obtained in this study was 11.8% and 41.2% under simulated solar and UVA irradiation, respectively, using Pd(0.24 wt%)/P25 in an aqueous solution of methanol (50 vol%). In the pilot-scale solar CPC, for Pd(0.24 wt%)//P25 catalysts in 5 vol% of methanol or glycerol as sacrificial agents, the quantum yield were 2.1 and 2.2%, respectively. When the concentration of the sacrificial agents decreased to 0.37 vol%, the quantum yields were 1.3 and 2.4% for methanol and glycerol, respectively. Compared to literature, the low noble metal content of these catalysts (0.25 wt%) seems to be a competitive factor considering their high price.

Simultaneous Photocatalytic Abatement of NO and SO2: Influence of the TiO2 Nature and Mechanistic Insights

Background: TiO2 is currently being incorporated into several construction materials, such as cement and asphalt because this photocatalyst can act as a passive system to reduce the concentration of typical urban pollutants like NOx and SO2 under solar illumination. Objective: In order to get further insights on the possible influence of the interaction between common pollutants, the present work investigates the mechanism of NOx photo-oxidation in the presence of SO2 traces over TiO2 samples of different textural and morphological characteristics. Methods: The performance for the photo-oxidation of NOx and SO2 in a dry air stream over TiO2 samples, both commercial and lab-prepared by hydrothermal and thermal methods, was evaluated by means of FTIR analyses of the gas phase. These materials were characterized by XRD, N2 adsorption isotherms, and DR UV-vis spectroscopy. Mechanistic studies were performed by in situ DRIFT under UV irradiation. Results: Photocatalytic tests showed a very efficient removal of the two selected pollutants using most of the TiO2 samples. In the case of SO2, elimination of these molecules is due not only to photocatalytic oxidation but also to a significant extent, to adsorption. Although in shorter periods, no byproducts are generated, following irradiation for several hours, the production of NO2 progressively increases and reaches 100 % selectivity over some photocatalyst. In situ DRIFTS analyses show the evolution of the surface composition and reveal the formation of the different types of surface nitrates with different symmetry. Under these operating conditions, a minor amount of sulfates are also formed. Conclusions: The presence of a low concentration of SO2 does not appear to be detrimental for NO removal. NO2 formation is delayed on the TiO2 samples with high specific surface area, which also tend to be more active. The spectroscopic results confirm the involvement of surface hydroxyls in the formation of adsorbed nitrate species.

New CeO2–TiO2, WO3–TiO2 and WO3–CeO2–TiO2 mesoporous aerogel catalysts for the low temperature selective catalytic reduction of NO by NH3

New mesoporous and well-structured aerogel catalysts (CeO2–TiO2, WO3–TiO2 and WO3–CeO2–TiO2) were elaborated via the sol–gel method, characterized by means of various techniques (XRD; N2-Physisorption at 77 K; NH3-TPD; H2-TPR; DRUV–Vis spectroscopy) and evaluated in the selective catalytic reduction (SCR) of NO by NH3. The results reveal that all the aerogel catalysts develop essentially the diffraction peaks of TiO2 anatase phase and are classified as mesoporous materials with a high surface area (70 < SBET < 106 m2 g−1), large porosity (0.27 < VPT < 0.46 cm3 g−1) and nanometer size of crystallites (8–15 nm). The addition of Ce and/or W influences differently the structure, texture, crystallites size, surface oxygen concentration, total acidity and redox ability of aerogel samples and clearly affects their NO-SCR activity which follows this order: TiO2 < WO3–TiO2 < CeO2–TiO2 < WO3–CeO2–TiO2. It was also found that cerium species are more active in the low temperature NO-SCR reaction than tungsten ones (NO conversions obtained at 300 °C using CeO2–TiO2 and WO3–TiO2 were 75 and 0%, respectively). On the other hand, it was suggested that the interactions between Ce and W species play a key role in improving the reactivity of WO3–CeO2–TiO2 catalyst in the SCR of NO by NH3. Interestingly, the NO conversion into N2 reaches 85% at 300 °C and exceeds 90% between 320 and 400 °C over this novel meso-structured aerogel catalyst.

Promotional effect of ceria on the catalytic behaviour of new V2O5–WO3–TiO2 aerogel solids for the DeNOx process

New cerium and/or tungsten modified V2O5–TiO2 aerogel catalysts (V2O5–TiO2,V2O5–WO3–TiO2, V2O5–CeO2–TiO2 and V2O5–WO3–CeO2–TiO2) were successfully developed, by associating the sol gel procedure and supercritical drying approach. A combination of various analytical techniques, including XRD, N2-Physisorption at 77 ​K, DRUV-Vis spectroscopy, NH3-TPD and H2-TPR, was used to characterize the obtained solids. Their catalytic performances were evaluated in the low temperature NO-SCR by NH3. The results reveal that all the materials exhibit high cristallinity of TiO2 anatase phase and developed mesoporous texture. The addition of tungsten (W) increases the surface acidity of V2O5–TiO2 and thereby enhances its reactivity at high temperatures (>420 ​°C). However, the addition of cerium (Ce) improves the redox properties of the latter catalyst and increases significantly its NO-SCR reactivity, especially at low temperatures. The NO-SCR activity increases over the aerogel systems, in the 200–400 ​°C temperature range, following this order: V2O5–WO3–TiO2 ​< ​V2O5–TiO2 ​< ​V2O5–CeO2–TiO2 ​< ​V2O5–WO3–CeO2–TiO2. The new V2O5–WO3–CeO2–TiO2 system was found to be the most active catalyst for converting NO into N2 (with 60% and 90% NO conversions at 250 ​°C and between 320 and 420 ​°C, respectively). The highest SCR activity of this new aerogel solid if compared to the other samples was essentially correlated with a good reactivity of its acidic and redox sites which in turn was related to the existence of strong interactions between cerium and the other active elements (mostly Ce↔ V and Ce ↔ W).

Facile methodology to generate Cu2O/TiO2 heterojunction on FTO electrode for photoelectroreduction of nitrate

Easy and low-cost synthesis of a Cu2O/TiO2/FTO electrode is proposed. The Cu2O/TiO2 heterojunction was synthesized by sintering TiO2 nanoparticles on an FTO electrode surface, followed by a Cu2O electrochemical deposition step. Characterization of the electrode was performed by FE-SEM-EDX microscopy, Raman and UV–Vis DR spectroscopy, and electrochemical methods. The photoelectrochemical behavior was characterized, and the p-type character material was confirmed. The reduction of nitrate to nitrite was performed using the Cu2O/TiO2/FTO electrode under Xe lamp illumination with lower overpotentials than those commonly used in this electrochemical process. Nitrate/nitrite conversion was achieved with a promising result of about 22% conversion at −0.05 V RHE.

An excellent Z-scheme Ag2MoO4/Bi4Ti3O12 heterojunction photocatalyst: Construction strategy and application in environmental purification

Herein we have designed an excellent type of Z-scheme Ag2MoO4/Bi4Ti3O12 (AMO/BTO) heterojunction photocatalysts by immobilizing AMO particles onto rod-like BTO hierarchical architectures. The formation of Z-scheme AMO/BTO heterostructures was verified by various characterization techniques including XRD, UV–vis DR spectroscopy, SEM, TEM, XPS and FTIR spectroscopy. PL spectroscopy, photocurrent response and EIS analyses suggest that the creation of AMO/BTO heterojunctions is conducive to the efficient separation of photoexcited electron-hole pairs. The photocatalytic performances of the AMO/BTO composites were investigated by simulated-sunlight driving photodegradation of methylene blue (MB), tetrabromobisphenol A (TBBPA), tetracycline hydrochloride (TC), phenol and methyl orange (MO)/rhodamine B (RhB)/MB mixture solutions. It is demonstrated that the AMO/BTO heterojunction photocatalysts are endowed with excellent photodegradation performances much higher than that of bare AMO and BTO. For example, the photodegradation rate of MB by using 30 wt%AMO/BTO — confirmed to be the optimal composite sample — is about 17.0 and 14.7 times as high as that by using bare BTO and AMO, respectively. A Z-scheme electron transfer mechanism was proposed to elucidate the enhanced photodegradation performances of the AMO/BTO heterojunction photocatalysts.

New Mn-TiO2 aerogel catalysts for the low-temperature selective catalytic reduction of NOx

A new series of Mn-based catalysts (Mn-TiO2, Ce-Mn-TiO2, Mn-TiO2-SO42–, and Ce-Mn-TiO2-SO42–) were successfully elaborated using the sol–gel method associated with supercritical drying approach for the low-temperature NO-SCR by NH3. The physicochemical properties of aerogel powders were examined by XRD, N2-Physisorption at 77 K, NH3-TPD, H2-TPR, and DRUV-Vis spectroscopy. It was shown that all the catalysts develop essentially the diffraction peaks of TiO2 anatase phase and are characterized by a nanometer size (ranging between ~5 and 9 nm), developed mesoporous texture, high surface area (SBET > 104 m2/g) and large porosity (VPT > 0.24 cm3/g). The incorporation of Ce and/or SO42– influences differently the structural, textural, acidic, and redox properties of Mn-derived sol–gel catalysts and consequently affects their SCR activity. High NO conversions (>75%) into essentially N2O are obtained at low temperatures (150–270 °C) over Mn-TiO2 and Ce-Mn-TiO2 aerogel systems. The addition of sulfate modifies the nature of Mn species and noticeably reduces the low-temperature reactivity of catalysts (T < 300 °C). However, it induces, thanks to the contribution of many strong acid sites, a substantial increase of the NO conversion into N2 at higher temperatures (T > 300 °C) leading to highly active and N2-selective Mn-TiO2-SO42– and Ce-Mn-TiO2-SO42– sulfated catalysts. Above 90% NO conversion into N2 (100%) was reached, in the NO-SCR by NH3, over the new Ce-Mn-TiO2-SO42– aerogel catalyst, in the 450–500 °C temperature range.