Photocatalytic epoxidation of propylene with Bi2WO6-based catalyst supported on glass beads

The photo activities of some photo-catalysts including TiO2, Bi2WO6 and Bi2WO6-TiO2 (in various mixing ratios) were evaluated for photo-epoxidation of propylene. The photocatalytic epoxidation reaction was performed in gas-phase under atmospheric pressure. Typical reaction mixture of C3H6:O2:N2 corresponding to the ratio 1:1:18, afforded PO (PO) in addition to other products such as acetone, acetaldehyde and propanal as observed by the FTIR-GCMS tandem analysis. It was established from the results that Bi2WO6-TiO2 photo-catalysts were more preferable for selectivity of PO peaking at 49%. The highest formation rate of PO achieved was 111μmol g cat-1 h-1 over 12mol% Bi2WO6-TiO2 ratio in a typical flow reaction for 1h at 345 K under UVA illumination. Under this condition the selectivity of products was also observed to be very stable. Further study on the effect of light intensity revealed that increasing the light intensity from 0.1 to 0.3mWcm-2 significantly increased the selectivity of PO by 5%. Higher intensity depreciated the PO selectivity. In order to study the effect of temperature on the photocatalytic epoxidation reaction, a systematic approach was followed. As raising the reaction temperature influences the distribution of products significantly, a temperature range of 335-355 K was used in the optimised reaction condition. At 355 K, it was observed that the formation of propanal was favoured which was attributed to its inhibition to be transformed into propionic acid. However, raising the reaction temperature was observed to affect the rate of reaction in two ways: first, the adsorption of PR on to the photo-catalyst which causes a decrease in the reaction efficiency was reduced and secondly, the desorption of products of reaction which in turn reveals more active sites, was improved.</p

Enhanced photocatalytic hydrogen production of S-scheme TiO2/g-C3N4 heterojunction loaded with single-atom Ni

S-scheme heterostructure photocatalysts can achieve highly efficient solar energy utilization. Here, single-atom Ni species were deposited onto TiO2/g-C3N4 (TCN) composite photocatalyst with an S-scheme heterojunction for highly efficient photocatalytic water splitting to produce hydrogen. Under solar irradiation, it realized the hydrogen production activity of 134 µmol g–1 h–1, about 5 times higher than the TCN without atomic Ni. In-situ Kelvin probe force microscopy characterization and the density functional calculation certify that by forming the S-scheme heterojunction, the photo-excited electrons from the TiO2 combine with the photogenerated holes at the coupled g-C3N4 driven by a built-in electric field. More importantly, the single-atom Ni species stabilized the photogenerated electrons from the g-C3N4 could effectively enhance the charge separation between the holes on the valence band of TiO2 and electrons at the conduction band of g-C3N4. Meanwhile, the Ni atoms act as the surface catalytic centers for the water reduction reaction, which greatly improves the reactivity of the photocatalyst. The present work provides a new approach for developing noble metal-free heterojunctions for high-efficiency photocatalysis.</p

Enhanced photocatalytic hydrogen production of S-scheme TiO2/g-C3N4 heterojunction loaded with single-atom Ni

S-scheme heterostructure photocatalysts can achieve highly efficient solar energy utilization. Here, single-atom Ni species were deposited onto TiO2/g-C3N4 (TCN) composite photocatalyst with an S-scheme heterojunction for highly efficient photocatalytic water splitting to produce hydrogen. Under solar irradiation, it realized the hydrogen production activity of 134 µmol g–1 h–1, about 5 times higher than the TCN without atomic Ni. In-situ Kelvin probe force microscopy characterization and the density functional calculation certify that by forming the S-scheme heterojunction, the photo-excited electrons from the TiO2 combine with the photogenerated holes at the coupled g-C3N4 driven by a built-in electric field. More importantly, the single-atom Ni species stabilized the photogenerated electrons from the g-C3N4 could effectively enhance the charge separation between the holes on the valence band of TiO2 and electrons at the conduction band of g-C3N4. Meanwhile, the Ni atoms act as the surface catalytic centers for the water reduction reaction, which greatly improves the reactivity of the photocatalyst. The present work provides a new approach for developing noble metal-free heterojunctions for high-efficiency photocatalysis.</p

Driving NiTiO3 photocatalyst for oxygen evolution reaction with near-infrared light

A nickel titanate (NTO) photocatalyst has been developed for the oxygen evolution reaction (OER) with an exceptionally broad light wavelength excitation ranging from visible to infrared. Specifically, by loading CoOxas the co-catalyst, the apparent quantum yields for the OER were ca. 2.2%, 1.0%, and 0.8% at wavelengths of 470, 760, and 850 nm, respectively. The achievements reveal that the NTO photocatalyst is highly efficient even under illumination with near-infrared (NIR) light, which confers the potential for highly efficient solar-driven oxidation reactions.</p

Rational design of liquid metal organic frameworks for the enhanced CO2 absorption and their photocatalytic reduction

Metal organic frameworks (MOFs) has been widely investigated as co-catalysts for photocatalysis owing to their unique property for controlling the reaction kinetics. They are generally presented in a solid state. Recent studies have presented MOF in the liquid phase, meanwhile preserving the framework structure. Acting as a co-catalyst, significantly improved efficiency has been realized for photocatalytic CO2 reduction. This concept article focuses on the chemical principle of liquid MOF (LMOF). Their applications in CO2 adsorption and the photocatalytic CO2 reduction have been discussed with showing key examples. In addition, the other relevant applications of LMOF have been presented. </p

Linear dichroism electron scattering from chiral surfaces

The adsorption of R-phenylglycine on Cu(1 1 0) surfaces shows that the periodic superstructure of the chiral overlayer destroys the substrate mirror plane symmetry. Here, we report on the novel linear dichroism electron scattering method to determine the chirality, based on the unique symmetry of the chiral surface. The details of the molecular structure, with the absolute surface chirality, are derived from the azimuthal variation of intensity of individual vibrational modes

Highly efficient ultrafiltration membrane performance of PES@microcrystalline cellulose extracted from waste fruits for the removal of BrO3- from drinking water samples

New mixed-matrix ultrafiltration membranes (MMMs) made of polyethersulfone (PES) and microcrystalline cellulose (MCC) were created utilizing a nonsolvent induced phase separation (NIPS) approach for the remediation of bromate (BrO3-) from aqueous medium. The influence of MCC integrated on the contact angle, porosity, water flux, and BrO3- adsorption performance was also examined. The addition of MCC, up to 5 wt%, resulted in a significant decline in the contact angle from 60.1° of neat PES to 43.1°, indicating an increase in membrane hydrophilicity. Moreover, MCC incorporation at 1, 3, and 5 wt% concentrations led to an enhancement in the water flux to 169, 178, and 180 L m-2 h-1, respectively, indicating the improved membrane permeability. MCC-integrated PES membranes exhibited enhanced antifouling properties, as demonstrated by the achieved high flux recovery ratio (99%) of the 5% MCC-containing membrane. Furthermore, all MCC-integrated PES membranes exhibited superior performance in the removal of bromate ions (BrO3-), with rejection rates of 60.8%, 80.2%, and 92% for 1%, 3%, and 5% MCC, respectively, which was much greater than that of the virgin PES membrane

Highly sensitive room-temperature detection of ammonia in the breath of kidney disease patients using Fe2Mo3O8/MoO2@MoS2 nanocomposite gas sensor

A novel Fe2Mo3O8/MoO2@MoS2 nanocomposite is synthesized for extremely sensitive detection of NH3 in the breath of kidney disease patients at room temperature. Compared to MoS2, α‐Fe2O3/MoS2, and MoO2@MoS2, it shows the optimal gas‐sensing performance by optimizing the formation of Fe2Mo3O8 at 900 °C. The annealed Fe2Mo3O8/MoO2@MoS2 nanocomposite (Fe2Mo3O8/MoO2@MoS2‐900 °C) sensor demonstrates a remarkably high selectivity of NH3 with a response of 875% to 30 ppm NH3 and an ultralow detection limit of 3.7 ppb. This sensor demonstrates excellent linearity, repeatability, and long‐term stability. Furthermore, it effectively differentiates between patients at varying stages of kidney disease through quantitative NH3 measurements. The sensing mechanism is elucidated through the analysis of alterations in X‐ray photoelectron spectroscopy (XPS) signals, which is supported by density functional theory (DFT) calculations illustrating the NH3 adsorption and oxidation pathways and their effects on charge transfer, resulting in the conductivity change as the sensing signal. The excellent performance is mainly attributed to the heterojunction among MoS2, MoO2, and Fe2Mo3O8 and the exceptional adsorption and catalytic activity of Fe2Mo3O8/MoO2@MoS2‐900 °C for NH3. This research presents a promising new material optimized for detecting NH3 in exhaled breath and a new strategy for the early diagnosis and management of kidney disease.</p

Chitosan-carboxylic acid grafted multifunctional magnetic nanocomposite as a novel adsorbent for effective removal of methylene blue dye from aqueous environment

In this work, magnetite nanoparticle decorated graphene oxide (MGO) is modified with triethylenetetramine (TETA), which is supported by maleated chitosan (MACS), named MGO@TETA@MACS. The novel magnetic nanohybrid is successfully fabricated via an in situ coprecipitation method, which is for methylene blue (MB) uptake from liquid phase environment. XRD, FTIR, TGA, nitrogen isotherm, SEM, and Zeta potential experiments were utilized to explore the MGO@TETA@MACS nanocomposite. The mean particle size and surface area of MGO@TETA@MACS were measured to be 11.5 nm and 128.04 m2·g−1, respectively. The nonlinear kinetic and isotherm models were utilized to evaluate the adsorption equilibrium. Data analysis revealed that the uptake kinetics fits the PFO model while the adsorption equilibrium follows the Langmuir isotherm. The maximum adsorption capacity of MGO@TETA@MACS nanocomposite, estimated from Langmuir isotherm, was 247.37 mg/g at the ambient temperature. Thermodynamic calculations confirmed the exothermic and spontaneous nature of the MB decontamination.</p

Depth-profiling analysis of ZnO layers with three morphologies by direct-current glow discharge mass spectrometry

• The capability of direct-current glow discharge mass spectrometry (dc-GD-MS) was demonstrated for depth-profiling analysis of zinc oxide (ZnO) layers on steel substrates. • ZnO-1/steel fabricated by magnetron sputtering presented superior performance with a high depth resolution of 0.22?µm and a clear interface between the ZnO layer and steel substrate. • The effects of layer morphology, thickness and sputtering rate on depth resolutions were investigated and layer morphology had greater impact on depth resolutions