Selective and stable visible-light-prompted scavenger-free photoelectrochemical strategy based on a ternary ErVO4/P@g-C3N4/SnS2 nanocomposite for the detection of lead ions in different water samples

Lead ions (Pb2+) are heavy metal environmental pollutants that can significantly impact biological health. In this study, the synthesis of a ternary nanocomposite, ErVO4/P@g-C3N4/SnS2, was achieved using a combination of hydrothermal synthesis and mechanical grinding. The as-fabricated photoelectrochemical (PEC) sensor was found to be an ideal substrate for Pb2+ detection with high sensitivity and reliability. The ErVO4/P@g-C3N4/SnS2/FTO was selected as the substrate because of its remarkable and reliable photocurrent response. The Pb2+ sensor exhibited a low detection limit of 0.1 pM and a broad linear range of 0.002-0.2 nM. Moreover, the sensor exhibited outstanding stability, selectivity, and reproducibility. In real-time applications, it exhibited stable recovery and a low relative standard deviation, ensuring reliable and accurate measurements. The as-prepared PEC sensor was highly stable for the detection of Pb2+ in different water samples. This promising characteristic highlights its significant potential for use in the detection of environmental pollutants.

Fabrication of wide temperature FexCe1-xVO4 modified TiO2-graphene catalyst with excellent NH3-SCR performance and strong SO2/H2O tolerance

Selective catalytic reduction of NO with NH3 (NH3-SCR) is one of the most common technique for elimination of NOx. The promotional effect of Fe additive on the NH3-SCR activity of the CeVO4/TiO2-graphene (GE) is systematically studied. The results exhibited that the low-temperature NOx conversion could be enhanced dramatically via the addition of Fe and Fe0.5Ce0.5VO4/TiO2-GE displayed the highest conversion of NOx in the wide temperature window (200-400 °C). It is because that Fe3+ + Ce3+ ↔ Fe2+ + Ce4+ facilitated the oxidization of NO to NO2 at low temperature and led to the "Fast SCR," thereby raising the SCR performance. What is more, the introduction of Fe enhanced redox ability, the surface relative percentage of Ce3+, V5+ and the chemical adsorbed oxygen. Furthermore, the high surface concentration of Ce3+ species can produce more active oxygen and leads to the "Fast SCR" reaction. In addition, the Fe0.5Ce0.5VO4/TiO2-GE catalyst showed excellent H2O/SO2 tolerance, which may be due to the decomposition of ammonium bisulphite under high temperature and the hydrophobicity of graphene. What is more, it displayed outstanding the stability. This work would provide theoretical reference for the practical application of NOx abatement via NH3-SCR.

Ce1−xFexVO4 with Improved Activity for Catalytic Reduction of NO with NH3

A series of Ce1−xFexVO4 (x = 0, 0.25, 0.50, 0.75, 1) catalysts prepared by modified hydrothermal synthesis were used for selective catalytic reduction (SCR) of NOx with NH3. Among them, Ce0.5Fe0.5VO4 showed the highest catalytic activity. The catalysts were characterized by X-ray diffraction (XRD), N2 adsorption–desorption, scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), X-ray fluorescence (XRF), X-ray photoelectron spectroscopy (XPS), temperature-programmed reduction using H2 (H2-TPR), and temperature-programmed desorption of NH3 (NH3-TPD). The results indicated the formation of Ce-Fe-V-O solid solutions. The average oxidation states (AOS) of Ce, Fe, V, and O atoms changed obviously with the incorporation of Fe3+ into CeVO4, and the acidity of Ce0.5Fe0.5VO4 differs from that of CeVO4 and FeVO4. The presence of more acid sites and a sharp increase in active oxygen species in Ce0.5Fe0.5VO4 effectively improved the selective catalytic reduction (SCR) activity.

Optimizing the Microstructure of SnO2-CeO2 Binary Oxide Supported Palladium Catalysts for Efficient and Stable Methane Combustion

The preparation of palladium-based catalysts with both high catalytic activity and hydrothermal stability currently appears as a critical topic in methane combustion. Herein, we propose a facile strategy to boost the performance of SnO₂-CeO₂ binary oxide supported palladium catalysts by tuning the composition of supports. The coexistence of SnO₂ and CeO₂ phases in an appropriate ratio is favorable for the formation of both Pd_xCe_1-xO_2-δ and Pd_xSn_1-xO_2-δ solid solutions due to the reduced crystallite size. This unique microstructure could enhance the metal-support interaction to stabilize the active PdO phase and promote its reoxidation, meanwhile generating more oxygen vacancies to improve the reducibility of PdO. On account of the facilitated conversion of PdO ↔ Pd, coupled with the low-temperature dissociation of methane promoted by abundant active oxygen species, the Pd/5Sn5Ce catalyst exhibits a superior catalytic activity with a T₉₉ of ca. 360 °C, a robust stability under both dry and wet conditions, and an excellent thermal stability during heating-cooling light-off tests.

TiO2-modified CeVO4 catalyst for the selective catalytic reduction of NOx with NH3

A series of TiO2-modified CeVO4 catalysts were prepared by the homogeneous precipitation method, among which the CeVTi5 catalyst showed the best low-temperature NH3-selective catalytic reduction (NH3-SCR) activity under high GHSV....

The effect of SO2 on the structural evolution of a supported Mn2V2O7 catalyst and its DeNOx performance

Mn₂V₂O₇/TiO₂ can decompose to form sulfated VO_x and MnSO₄ on TiO₂ in the presence of SO₂, and the corresponding DeNO_x efficiency increases above 250 °C but it decreases below 250 °C.

Recent Progress on Improving Low-Temperature Activity of Vanadia-Based Catalysts for the Selective Catalytic Reduction of NOx with Ammonia

Selective catalytic reduction of NOx with NH3 (NH3-SCR) has been successfully applied to abate NOx from diesel engines and coal-fired industries on a large scale. Although V2O5-WO3(MoO3)/TiO2 catalysts have been utilized in commercial applications, novel vanadia-based catalysts have been recently developed to meet the increasing requirements for low-temperature catalytic activity. In this article, recent progress on the improvement of the low-temperature activity of vanadia-based catalysts is reviewed, including modification with metal oxides and nonmetal elements and the use of novel supports, different synthesis methods, metal vanadates and specific structures. Investigation of the NH3-SCR reaction mechanism, especially at low temperatures, is also emphasized. Finally, for low-temperature NH3-SCR, some suggestions are given regarding the opportunities and challenges of vanadia-based catalysts in future research.

SO2-Tolerant NOx Reduction by Marvelously Suppressing SO2 Adsorption over FeδCe1-δVO4 Catalysts

SO₂-tolerant selective catalytic reduction (SCR) of NO_x at low temperature is still challenging. Traditional metal oxide catalysts are prone to be sulfated and the as-formed sulfates are difficult to decompose. In this study, we discovered that SO₂ adsorption could be largely restrained over Fe_δCe_1-δVO₄ catalysts, which effectively restrained the deposition of sulfate species and endowed catalysts with strong SO₂ tolerance at an extremely low temperature of 240 °C. The increasing oxygen vacancies, enhanced redox properties, and improved acidity contributed to the SCR activity of the Fe_δCe_1-δVO₄ catalyst. The reaction pathway changed from the reaction between bidentate nitrate and the NH₃ species over CeVO₄ catalysts via the Langmuir-Hinshelwood mechanism to that between gaseous NO_x and the NH₄⁺/NH₃ species over Fe_δCe_1-δVO₄ catalysts via the Eley-Rideal mechanism. The effective suppression of SO₂ adsorption allowed Fe_δCe_1-δVO₄ catalysts to maintain the Eley-Rideal pathways on account of the reduced formation of sulfate species. This work demonstrated an effective route to improve SO₂ tolerance via modulating SO₂ adsorption on Ce-based vanadate catalysts, which presented a new point for the development of high-performance SO₂-tolerant SCR catalysts.

Modification of composite catalytic material CumVnOx@CeO2 core-shell nanorods with tungsten for NH3-SCR

Novel composite material CumVnOx-NF@Ce-MOF nanorods with a core-shell structure were successfully fabricated by the in situ growth of Ce-MOF on electrospun copper vanadate precursor nanofibers. Following calcination at 500, 600 and 700 °C, Cu2V2O7@CeO2, Cu3(VO4)2@CeO2 and Cu11O2(VO4)6@CeO2, respectively, were obtained. The CeO2 shell not only protected the copper vanadate nanofibers from breaking apart during the calcination process, but also induced an interaction between Ce, Cu and V species, which resulted in an excellent redox capacity. This revealed its potential as a catalyst for the selective catalytic reduction of nitrogen oxides with NH3 (NH3-SCR). Further surface modulation was accomplished by WOx anchoring on the shell of CumVnOx@CeO2. According to a series of characterizations, the crystallinity of surface ceria on CumVnOy@CeO2-WOx was apparently reduced and the amount of acid on its surface was also significantly increased. In addition, different calcination temperatures also had nonnegligible effects on the amount of surface acid as well as the redox capacity of the composite catalytic material CumVnOy@CeO2-WOx. With the largest total quantity of acid sites as well as a suitable balance between acidity and reducing ability, the Cu3(VO4)2@CeO2-WOx calcined at 600 °C exhibited satisfactory catalytic performance in the NH3-SCR process, and the NO conversion could remain above 90% at 230-380 °C.

Facile Fabrication of Ce/V-Modified Multi-Channel TiO2 Nanotubes and Their Enhanced Selective Catalytic Reduction Performance

To optimize one-dimensional (1D) TiO₂ nanofibers, tailor-made multi-channel TiO₂ nanotubes have been successfully fabricated by electrospinning technology. After loading with Ce and V, the CeVTi-tube catalyst exhibited a broad working temperature window and acceptable resistance to H₂ O and SO₂ for elimination of NO_x . The corresponding analysis revealed that the multi-channel structure provided more surface adsorbed oxygen species and that the wall of nanotubes anchored active components efficiently, which was beneficial to improve the stability as well as dispersion of the active components. Besides, a synergistic effect between Ce and V easily occurred at the CeVTi-tube catalyst, and its reducibility was significantly improved since the electron transformation between Ce and V was dramatically enhanced. Consequently, the tailor-made multi-channel CeVTi-tube catalyst exhibited satisfied de-NO_x efficiency at the temperature range of 220-460 °C. It seemed that the multi-channel TiO₂ nanotubes hold great potential as an excellent carrier for SCR catalysts.

Promotional effects of modified TiO2- and carbon-supported V2O5- and MnOx-based catalysts for the selective catalytic reduction of NOx: a review

This review presents the promotional effects of transition metal modification over TiO₂- and carbon-supported V₂O₅- and MnO_x-based SCR catalysts.

Enhancing Water Resistance of a Mn-Based Catalyst for Low Temperature Selective Catalytic Reduction Reaction by Modifying Super Hydrophobic Layers

OMS-2 catalysts exhibit excellent selective catalytic reduction (SCR) activity at low temperature but weak H₂O resistance restricts its industrial application. To remarkably improve the water resistance of Mn-based catalysts is a key technical problem. In this work, the H₂O endurance and self-cleaning properties of OMS-2 catalysts are remarkably improved by the facile process, construction of hydrophobic coating. The performance of the hydrophobic layer on the bulk OMS-2 catalyst surface could be effectively controlled by adjusting the polydimethylsiloxane (PDMS) vapor deposition temperature. It is discovered that the 200 °C catalyst obtained super hydrophobic properties and formed with a contact angle of 160.3°, which not only exhibited satisfactory NH₃-SCR activity at low temperatures (140-300 °C) but also dramatically improved H₂O endurance and self-cleaning performance. Moreover, the mechanism of improving H₂O resistance and stability of the 200 °C catalyst was investigated in detail through a series of characterizations. Although the SCR activity of the 200 °C catalyst decreased slightly because of the combination of some active species (O_α and Mn³⁺) with PDMS, the H₂O passivation of the active species was eliminated. The advantage of self-cleaning was confirmed by the analysis of surface species and simulation experiments, which could avoid the accumulation of intermediates on the surface and promote the stability of the OMS-2 catalyst for NH₃-SCR at low temperature. This method of constructing special coating might be a huge step to remarkably improve the H₂O endurance properties of the catalyst and provided a new concept for future industrial application.

Preparation and Characterization of Magnetic Fe3O4/CdWO4 and Fe3O4/CdWO4/PrVO4 Nanoparticles and Investigation of Their Photocatalytic and Anticancer Properties on PANC1 Cells

Fe3O4/CdWO4 and Fe3O4/CdWO4/PrVO4 magnetic nanoparticles were prepared at different molar ratios of PrVO4 to previous layers (Fe3O4/CdWO4) via the co-precipitation method assisted by a sonochemical procedure, in order to investigate the photocatalytic performance of these systems and their cytotoxicity properties. The physico-chemical properties of these magnetic nanoparticles were determined via several experimental methods: X-ray diffraction, energy dispersive X-ray spectroscopy, Fourier transformation infrared spectroscopy and ultraviolet-visible diffuse reflection spectroscopy, using a vibrating sample magnetometer and a scanning electron microscope. The average sizes of these nanoparticles were found to be in the range of 60-100 nm. The photocatalytic efficiency of the prepared nanostructures was measured by methylene blue degradation under visible light (assisted by H2O2). The magnetic nanosystem with a 1:2:1 ratio of three oxide components showed the best performance by the degradation of ca. 70% after 120 min of exposure to visible light irradiation. Afterwards, this sample was used for the photodegradation of methyl orange, methyl violet, fenitrothion, and rhodamine-B pollutants. Finally, the mechanism of the photocatalytic reaction was examined by releasing ˙OH under UV light in a system including terephthalic acid, as well as O2-, OH, and hole scavengers. Additionally, the cytotoxicity of each synthesized sample was assessed using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay against the human cell line PANC1 (cancer), and its IC50 was approximately 125 mg/L.

Porous hollow CoInOx nanocubes as a highly efficient catalyst for the catalytic combustion of toluene

Porous hollow HC-CoInOx nanocubes were synthesized via a SiO2 template strategy involving a cobalt-based metal-organic framework derived from a Prussian Blue analogue. As a heterogeneous catalytic material for the catalytic combustion of toluene, the hollow HC-CoInOx nanocubes displayed superior catalytic performance (T90 = 178 °C) and greatly reduced the activation energy for toluene oxidation due to their large surface area, the formation of surface dangling bands and oxygen vacancies, and increased number of weak acid sites. In comparison, the C-CoInOx sample (without the introduction of a SiO2 template) required a higher reaction temperature to achieve the same conversion of toluene (T90 = 345 °C). Especially, the insertion and coating of SiO2 in CoIn-PBA nanocubes greatly improves their thermal stability, and the nanocubic shape of the porous hollow HC-CoInOx sample can remain intact after roasting at 450 °C, while the nanocubic shape of the C-CoInOx sample without the introduction of SiO2 is partially damaged and suffers from serious aggregation under the same firing conditions. Simultaneously, the porous hollow HC-CoInOx nanocubes also exhibited excellent cycling and thermal stability for the catalytic combustion of toluene to CO2 and H2O.

Fabrication of homogeneous and highly dispersed CoMn catalysts for outstanding low temperature catalytic oxidation performance

A series of homogeneous and highly dispersed CoMnO_x bimetallic oxides with different ratios were prepared through pyrolysis of CoMn-MOF-71, which was applied to the catalytic oxidation of toluene.

Comprehensive study of the promotional mechanism of F on Ce–Mo/TiO2 catalysts for wide temperature NH3-SCR performance: the activation of surface Ti–F bonds

The CeFMoTiO_x catalyst was prepared via a solvothermal method. It confirmed that O_α was not only generated during the transformation between Ce⁴⁺ and Ce³⁺ but was also released from F⁻ species of the surface Ti–F bonds.