UV Vis Diffuse Reflectance Spectroscopy Research Articles

Photocatalytic efficiency of PVDF based binary and ternary nanocomposites of metal sulfides: A comparative study

Our present research work aims in providing a simple and economical technique of developing an efficient visible light active photocatalyst. Polyvinylidene fluoride (PVDF) based binary and ternary nanocomposites of metal sulfide nanostructures namely ZnS/PVDF and ZnS/CdS/PVDF were synthesized using a simple solvent casting technique. The photocatalytic efficiencies of the prepared composite films were studied towards the degradation of Malachite green dye under UV and visible light irradiation. Effective incorporation of nanomaterial fillers on the PVDF matrix was confirmed by X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray (EDX), Fourier Transform Infrared (FTIR) and UV–Vis Diffused Reflectance spectroscopy. The energy band gap of ZnS/PVDF and ZnS/CdS/PVDF, calculated using the Kubelka Munk Function from the Reflectance data were observed to be 3.64 eV and 2.52 eV respectively. Photodegradation studies show that ternary nanocomposite is a better photocatalyst as compared to binary nanocomposite under both UV and visible light irradiation.

Hydrothermal Synthesis of Bismuth Ferrite Hollow Spheres with Enhanced Visible-Light Photocatalytic Activity.

In recent years, semiconductor hollow spheres have gained much attention due to their unique combination of morphological, chemical, and physico-chemical properties. In this work, we report for the first time the synthesis of BiFeO3 hollow spheres by a facile hydrothermal treatment method. The mechanism of formation of pure phase BiFeO3 hollow spheres is investigated systematically by variation of synthetic parameters such as temperature and time, ratio and amount of precursors, pressure, and calcination procedures. The samples were characterized by X-ray powder diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy, and UV-vis diffuse reflectance spectroscopy. We observe that the purity and morphology of the synthesized materials are very sensitive to synthesis parameters. In general, the chemically and morphologically very robust hollow spheres have diameters in the range of 200 nm to 2 μm and a wall thickness of 50-200 nm. The synthesized BiFeO3 hollow spheres were applied as catalysts in the photodegradation of the model pollutant Rhodamine B under visible-light irradiation. Notably, the photocatalyst demonstrated exceptionally high removal efficiencies leading to complete degradation of the dye in less than 150 min at neutral pH. The superior efficiencies of the synthesized material are attributed to the unique features of hollow spheres. The active species in the photocatalytic process have been identified by trapping experiments.

Ag-Doped WO3 Nanoplates as Heterogenous Multifunctional Catalyst for Glycerol Acetylation, Electrocatalytic and Enhanced Photocatalytic Hydrogen Production.

Herein, we report a hydrothermal method to synthesize pristine and Ag-doped WO3 nanoplates and study their multifunctional competence in the accomplishment of enhanced catalytic organic conversion and highly efficient photocatalytic and electrocatalytic H2 evolution reactions. The as-synthesized nanoplates were characterized by using various techniques including X-ray diffraction, field emission scanning electron microscopy-energy-dispersive X-ray analysis, transmission electron microscopy, UV-vis diffuse reflectance spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, and BET surface area studies. The significant catalytic performance was shown by 1% Ag-doped WO3 nanoplates with 100% glycerol conversion and 90% triacetin selectivity. The photocatalytic activity was also examined toward water splitting H2 evolution reaction which demonstrates the highest H2 evolution of 12.06 mmol g-1 catalyst for 1% Ag-doped WO3 nanoplates in a time span of 8 h. Moreover, the electrocatalytic hydrogen evolution reaction was also monitored in acidic media (0.1 M H2SO4) which demonstrates good results for 1% Ag-doped WO3 nanoplates with a low overpotential of 0.53 V and a low Tafel slope of 40 mV dec-1.

Rapid Microwave-Assisted Synthesis of ZnIn2S4 Nanosheets for Highly Efficient Photocatalytic Hydrogen Production.

In this study, a facile and rapid microwave-assisted synthesis method was used to synthesize In2S3 nanosheets, ZnS nanosheets, and ZnIn2S4 nanosheets with sulfur vacancies. The two-dimensional semiconductor photocatalysts of ZnIn2S4 nanosheets were characterized by XRD, FESEM, BET, TEM, XPS, UV-vis diffuse reflectance, and PL spectroscopy. The ZnIn2S4 with sulfur vacancies exhibited an evident energy bandgap value of 2.82 eV, as determined by UV-visible diffuse reflectance spectroscopy, and its energy band diagram was obtained through the combination of XPS and energy bandgap values. ZnIn2S4 nanosheets exhibited about 33.3 and 16.6 times higher photocatalytic hydrogen production than In2S3 nanosheets and ZnS nanosheets, respectively, under visible-light irradiation. Various factors, including materials, sacrificial reagents, and pH values, were used to evaluate the influence of ZnIn2S4 nanosheets on photocatalytic hydrogen production. In addition, the ZnIn2S4 nanosheets revealed the highest photocatalytic hydrogen production from seawater, which was about 209.4 and 106.7 times higher than that of In2S3 nanosheets and ZnS nanosheets, respectively. The presence of sulfur vacancies in ZnIn2S4 nanosheets offers promising opportunities for developing highly efficient and stable photocatalysts for photocatalytic hydrogen production from seawater under visible-light irradiation.

Natural kaolinite modified black titanium dioxide for efficient visible light assisted photocatalysis

A novel black TiO2/kaolinite composite (bTK) was prepared by the hydrothermal method and tested as a photocatalyst. Morphology and structure of samples were systematically characterized by field emission scanning electronic microscopy (FESEM), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), UV–vis diffuse reflectance spectroscopy (UV–vis DRS) and X-ray photoelectron spectroscopy (XPS). The results showed that black TiO2 (bT) nanoparticles formed point defects were successfully coated as thin layers on the surface of kaolinite. The bTK composite had a narrower band gap and higher specific surface area. XPS results showed that Ti3+ and oxygen vacancies (Vo) existed in bT. The photocatalytic removal performance of bTK composite on methylene blue (MB) was near to 100% in 2 h, which was 32.1% higher than that of bT. Kinetic studies reveal that MB degradation process by the bTK corresponded well to zero-order kinetic.

Solar photocatalytic degradation of polyethylene terephthalate nanoplastics: Evaluation of the applicability of the TiO2/MIL-100(Fe) composite material

For the first time, TiO2/MIL-100(Fe) photocatalysts supported on perlite mineral particles prepared by the solvothermal/microwave methods and post-annealing technique were tested in the degradation of polyethylene terephthalate nanoplastics (PET NPs). Powder X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy, X-ray photoelectron spectroscopy, UV–vis diffuse reflectance spectroscopy, N2 physisorption, photoluminescence emission spectroscopy, photocurrent response, and electrochemical impedance spectroscopy were used to characterize the as-prepared materials. The response surface methodology approach was used to study the effects: pH of the NPs suspension and incorporated amount of MIL-100(Fe) on the TiO2/MIL-100(Fe) catalyst to optimize the photocatalytic degradation of the PET NPs under simulated solar light. The degradation of the PET NPs was evaluated by measuring turbidity and carbonyl index (FTIR) changes. The total organic carbon (TOC) in the solution during the degradation of the PET NPs was assessed to measure NPs oxidation into water-soluble degradation by-products. The active species involved in the photocatalytic degradation of PET NPs by the TiO2/MIL-100(Fe) composite was further examined based on trapping experiments. The use of 12.5 wt% TiO2/MIL-100(Fe) catalyst showed improved photocatalytic efficacy in the oxidation of PET NPs at pH 3 under simulated sunlight compared to bare TiO2. The increase in the carbonyl index (CI = 0.99), the reduction in the turbidity ratio (0.454), and the increase in the content of TOC released (3.00 mg/L) were possible with 12.5 wt% TiO2/MIL-100(Fe) material. In contrast, the PET NPs were slowly degraded by TiO2-based photocatalysis (CI = 0.96, turbidity ratio = 0.539, released TOC = 2.12 mg/L). The mesoporous TiO2/MIL-100(Fe) composites with high specific surface area, capacity to absorb visible light, and effective separation of photogenerated electron-hole charges clearly demonstrated the enhancement of the photocatalytic performance in the PET NPs degradation under simulated solar light.

Synthesis and characterization of tungsten trioxide (WO3) as photocatalyst against wastewater pollutants

In this work, crash precipitation technique was employed to synthesize a visible light-responsive tungsten trioxide (WO3) photocatalyst using ammonium paratungstate as tungsten precursor. The spray-dried (120 °C) and calcined (600 °C) WO3 powder was characterized by analyzing methods of XRD, PSD, BET and BJH, Raman, FESEM/EDX, FTIR, UV–vis DRS and XPS spectroscopy. X-ray diffraction (XRD) and Raman studies confirm the well crystalline monoclinic crystal structure. Scanning electron microscopy (SEM) images showed micron-sized spherical bulks of WO3 particles with needle-like morphology. A normal distribution with a d50 (median diameter) value of 6.0 μm was observed with particle size analysis. Much enhanced BET surface area of 102 g/m2 with wide pore size 1.8 nm is measured compared to commercially available WO3 that results in increased pollutants surface adsorption. Fourier transform infrared spectroscopy (FTIR) study demonstrated that the calcined sample surface is enriched with bonded hydroxyl groups, beneficial for powder particles activity. Photocatalyst band gap was calculated by considering the absorbance measurements recorded on UV–vis diffuse reflectance spectroscopy (DRS). The energy value of 2.6 eV was calculated which lies in the visible light region while X-ray photoelectron spectroscopy (XPS) analysis showed 6 + oxidation state for tungsten. Bulk WO3 sphere photocatalytic activity was evaluated through the exertion of synthetic textile methylene blue (MB) dye and sulfamethoxazole (SMX) pharmaceutical antibiotic. The obtained activity results showed 85% and 100% degradation for MB and SMX under 100 min visible light irradiation. We expect that our work may provide a new sample for energy production (H2) through water photolysis, gas sensing and soft matter research.

Degradation of tetracycline by activating persulfate with ZnFe2O4-Bi2MoO6 catalyst under visible light

The ZnFe2O4-Bi2MoO6 composite photocatalyst was applied to construct a persulfate activation system combined with photocatalysis. The composite material was synthesized by a simple hydrothermal method and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and UV–vis diffuse reflectance spectroscopy (UV-Vis DRS) to study the phase formation, morphology, valence state of elements and light absorption property, respectively. The experimental results showed that the degradation efficiency of tetracycline can reach 84 % in 40 min under visible light, with K2S2O8 as the co-catalyst. The principal advantage of this system is that it can be applied to a wide pH range (3−11) with negligible influence. This system is also less affected by anions (HCO32-, NO3-, Cl-,) and humic acid (HA). The excellent catalytic performance may be due to the retention of electron hole pairs with high redox ability after the construction of heterojunction and the formation of active radicals, O2•-, SO4•- and •OH. In addition, the ZnFe2O4/Bi2MoO6 composite catalyst showed good stability and recyclability.

High-Temperature Behavior of Laser Electrodispersion-Prepared Pd/ZSM-5 Hydrocarbon Traps under CO Oxidation Conditions.

Zeolites and metal-doped zeolites are now widely considered as low-temperature hydrocarbon traps to be a part of emission control systems in automobiles. However, due to the high temperature of exhaust gases, the thermal stability of such sorbent materials is of great concern. To avoid the thermal instability problem, in the present work, laser electrodispersion was used to deposit Pd particles on the surface of ZSM-5 zeolite grains (SiO2/Al2O3 = 55 and SiO2/Al2O3 = 30) to obtain Pd/ZSM-5 materials with a Pd loading as low as 0.03 wt.%. The thermal stability was evaluated in a prompt thermal aging regime involving thermal treatment at temperatures up to 1000 °C in a real reaction mixture (CO, hydrocarbons, NO, an excess of O2, and balance N2) and a model mixture of the same composition with the exception of hydrocarbons. Low-temperature nitrogen adsorption and X-ray diffraction analysis were used to examine the stability of the zeolite framework. Special attention was paid to the state of Pd after thermal aging at varied temperatures. By means of transmission electron microscopy, X-ray photoelectron spectroscopy, and diffuse reflectance UV-Vis spectroscopy, it was shown that palladium, having been initially located on the surface of zeolite, undergoes oxidation and migrates into the zeolite's channels. This enhances the trapping of hydrocarbons and their subsequent oxidation at lower temperatures.

Revealing electronic structure of nanostructured cobalt titanate via a combination of optical and electrochemical approaches toward water splitting and CO2 reduction

AbstractBackgroundThe shortage of clean energy has become a serious problem due to the rapid development of societies and the increasing consumption of fossil fuels. Metal oxide semiconductor nanomaterials have been studied as photo‐/electrocatalysts for water splitting in terms of clean energy generation. Applications of semiconductors depend on their electronic structures. Therefore, elucidating the electronic diagram is essential for determining the specific applications of novel semiconductors.ResultsHerein, we demonstrate using a combination of UV–visible diffuse reflectance spectroscopy (DRS) and Mott–Schottky analysis via electrochemical impedance spectroscopy for sketching the electronic diagram of nanostructured cobalt titanate (CoTiO3) prepared by the sol–gel method. UV–visible DRS studies reveal a band gap of 2.5 and 2.1 eV for direct and indirect transitions of prepared nanostructured materials, respectively. Mott–Schottky analysis shows a 0.8 V versus Ag/AgCl value for the flat band potential for CoTiO3. We further show the application of this diagram toward the interpretation of the electrochemical behavior of nanostructured CoTiO3 for electrochemical water splitting reactions and the electrochemical CO2 reduction reaction (eCO2RR).ConclusionThe presented electrochemical and photoelectrochemical studies demonstrate nanostructured CoTiO3 as an effective catalyst for electrochemical water oxidation and the eCO2RR. Moreover, our results provide valuable information for further investigation of water splitting and photovoltaic energy conversion. © 2023 Society of Chemical Industry (SCI).

Bio synthesis and characterization of tin oxide for photocatalytic, anti-microbial and anti-oxidant applications

The advancement of new synthetic ways for the preparation of monodispersed nanocrystals by the use of cheap, non-toxic and environmentally benign materials become a challenge to the research community in science. The present study deals with the biosynthesis of SnO2 nanoparticles making use of the extract of Garcinia Cambogia as reducing and stabilizing agent. This method is simple, efficient, economic, harmless and eco-friendly. The morphological, surface, and structural studies have been conducted by employing X-ray diffraction analysis (XRD), Transmission electron microscopy (TEM), Scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), Atomic force microscopy (AFM), Brunauer-Emmet-Teller (BET), Fourier -Transform Infrared spectroscopy (FT-IR) and Raman Spectroscopy. The thermal and optical studies have been performed using TG-DTA analysis, UV–Visible diffuse reflectance spectroscopy and Photoluminescence spectroscopy. The photocatalytic activity of NPs is investigated against methylene blue. Agar well diffusion method is used to study the antibacterial action of the SnO2 nanoparticles with Gram-positive S.aureus along with Gram-negative E. coli. The anti-oxidant activity of SnO2 nanoparticles is confirmed using the DPPH assay.

Influence of Synthetic Conditions on the Crystal Structure, Optical and Magnetic Properties of o-EuFeO3 Nanoparticles

In this paper, powders consisting of o-EuFeO3 nanoparticles were obtained by the co-precipitation method using two different precipitating agents (NH3 and (NH4)2CO3 solutions; corresponding products were denoted as samples S.1 and S.2, respectively) and followed by annealing for 1 h at 750, 850, and 950 °C. The magnetic, optical, and physicochemical characteristics of S.1 and S.2 were evaluated by means of EDXS (energy dispersive X-ray spectroscopy), PXRD (powder X-ray diffraction), TG/DSC (thermogravimetry/differential scanning calorimetry), FTIR (Fourier-transform infrared spectroscopy), TEM (transmission electron microscopy), UV-Vis DRS (Ultraviolet–Visible diffuse reflectance spectroscopy), and VSM (vibrating-sample magnetometry). The o-EuFeO3 structure was shown to be stable at annealed temperatures, and t = 850 °C is recommended for synthesizing such substances. The average size of o-EuFeO3 crystals is around 27 (S.1) and 34 nm (S.2). The results revealed a homogeneous distribution of the main elements on the samples’ surfaces, with morphology consisting of isometric and highly agglomerated nanoparticles. The bandgap value (Eg) of the synthesized samples was 2.31 (S.1) and 2.39 eV (S.2). Besides, these nanoparticles appeared to possess paramagnetic behavior.

Preparation of heterojunction C3N4/WO3 photocatalyst for degradation of microplastics in water

In this study, a WO3/g-C3N4 composite photocatalyst was synthesized via a hydrothermal method and characterized for its potential application in photocatalytic H2 generation from PET degradation. XRD analysis revealed that the hexagonal WO3 crystal structure was achieved after 10 h of hydrothermal time, with particles of suitable size for uniform loading on the g-C3N4 surface. SEM images showed the successful loading of WO3 nanorods onto the g-C3N4 surface, significantly increasing the specific surface area. FTIR and UV–vis diffuse reflectance spectroscopy confirmed the formation of a Z-type heterojunction between WO3 and g-C3N4. Photoluminescence measurements indicated a reduced rate of electron-hole pair recombination in the composite. The 30% WO3/g-C3N4 composite demonstrated a high H2 evolution rate of 14.21 mM and excellent stability in PET solution under visible light irradiation. 1H NMR and EPR spectroscopy analyses revealed the degradation of PET into small molecular compounds and the generation of active radicals, including ·O2−, during the reaction. Overall, the WO3/g-C3N4 composite exhibited promising potential for photocatalytic H2 production and PET degradation.

Elemental Mercury Removal from Natural Gas Using Nano-Tio2

The study focused on the utilization of titanium dioxide (TiO2) as a photo-catalyst for the treatment of natural gas contaminated with elemental mercury (Hg0). The catalyst was carefully characterized using various physical techniques, including transmission electron microscopy (TEM), energy dispersive X-ray analysis (EDAX), UV-visible diffuse reflectance spectroscopy (DRS), Brunauer-Emmett-Teller (BET), X-ray photoelectron spectroscopy (XPS) , and X-ray diffraction analysis (XRD). The results clearly demonstrated that TiO2 exhibited outstanding efficacy in oxidizing Hg0 when exposed to UV light. This phenomenon was ascribed to the excitation of photoelectrons within the valence band, leading to their transfer to the conduction band, generating photo-induced electrons that acted as reactive agents responsible for converting Hg0 into HgO. Notably, the activity of TiO2 under UV-visible light was significantly lower compared to TiO2 under UV light. The overall findings indicated that TiO2 under UV light exhibited the highest removal capacity, measured at 31.74 µg/g, followed by TiO2 under UV-visible light at 25.91 µg/g, and TiO2 in the dark at 20.89 µg/g. The study underscores the promising potential of TiO2 photo-catalyst for effectively eliminating Hg0 contamination in natural gas.

Microwave-assisted synthesis of nanostructured tin sulfide as a highly efficient visible-light active photocatalyst: Characterization, applications, and theoretical studies

In this study, nanostructured tin sulfide was synthesized using a facile microwave-assisted method. The as-prepared sample was further characterized via X-ray diffraction (XRD), Scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDS), UV–Visible Diffuse Reflectance Spectroscopy (DRS), Brunauer-Emmett-Teller (BET), Barrett-Joyner-Halenda (BJH) and Mott-Schottky analyses. Based on the results, the synthesized SnS is an n-type semiconductor and has a direct band gap of 1.32 eV. Photocatalytic activity of nanostructured SnS was then evaluated through degrading methylene blue (MB) under visible light in a cylindrical batch reactor. The results show that this highly efficient photocatalyst can degrade almost up to 83.06% of 14 mg/L pollutant within 10 min, which can be attributed to its relatively high specific surface area of 52.819 m2/g. In addition, the photocatalyst performance was studied from the isothermic, thermodynamic, and kinetic points of view. The results suggest that Fritz-Schlunder along with Baudu are the most appropriate models to describe the adsorption process (the first step of photochemical reactions), as they have the lowest error functions and highest correlation coefficients. Based on kinetic studies results, there is a good agreement between the pseudo-second-order adsorption kinetic model and our experimental data. Additionally, the corresponding structural parameters of SnS were compared by size-strain plot (SSP), and Williamson-Hall methods. Furthermore, a density functional theory (DFT) approach was conducted to get more insight into the electronic and structural properties of the SnS. In terms of the band structure, 1.35 eV of band gap energy (Eg) is obtained, which perfectly matches with the results of characterization tests (1.32 eV). Finally, the partial density of states curves indicate that the valence band maximum (VBM) is mainly generated from 3pS, 5sSn, and 5pSn states while the conduction band minimum (CBM) is made of 5pSn states. Consequently, the spin-up and spin-down curves are found to be highly symmetric, indicating the non-magnetic property of tin sulfide.

Novel Type-II Heterojunction Binary Composite (CdS/AgI) with Outstanding Visible Light-Driven Photocatalytic Performances toward Methyl Orange and Tetracycline Hydrochloride.

In this study, an effective type-II heterojunction CdS/AgI binary composite was constructed by an in situ precipitation approach. To validate the successful formation of heterojunction between AgI and CdS photocatalysts, the synthesized binary composites were characterized by various analytical techniques. UV-vis diffuse-reflectance spectroscopy (UV-vis DRS) revealed that heterojunction formation led to a red shift in the absorbance spectra of the CdS/AgI binary composite. The optimized 20AgI/CdS binary composite showed a least intense photoluminescence (PL) peak indicating highly improved charge carrier (e-/h+ pairs) separation efficiency. The photocatalytic efficiency of the synthesized materials was assessed based on the degradation of methyl orange (MO) and tetracycline hydrochloride (TCH) in the presence of visible light. Compared to bare photocatalysts and other binary composites, the 20AgI/CdS binary composite showed the highest photocatalytic degradation performances. Additionally, the trapping studies showed that superoxide radical anion (O2•-) was the most dominant active species involved in photodegradation processes. Based on the results of active species trapping studies, a mechanism was proposed to describe the formation of type-II heterojunctions for CdS/AgI binary composite. Overall, the synthesized binary composite has tremendous promise for environmental remediation due to its straightforward synthesis approach and excellent photocatalytic efficacy.

Photocatalytic oxidation of benzyl alcohol coupled with p-dinitrobenzene reduction over poly(o-phenylenediamine) nanowires-decorated Gd-TiO2 nanorods

Simultaneous oxidation of benzyl alcohol (BA) and reduction of p-dinitrobenzene (p-DNB) over Gd-doped TiO2nanorods decorated with poly(o-phenylenediamine, PoPD) nanowires was reported in this work. The doping of TiO2 with Gd induced surface defects, i.e., oxygen vacancy (OV) and the Ti3+–on-Ti4+site, while incorporating PoPD highly enhanced the light absorption capability and electron conductivity of TiO2nanorods,as confirmed by UV–vis diffuse reflectance spectroscopy (DRS) and electrochemical measurements, respectively. BA was selectively oxidized by photogenerated h+to form benzaldehyde with a yield of 70.5% in water and 90.6% in acetonitrile solvent. Conversely, p-DNB was selectively reduced to p-nitroaniline (p-NA) with a yield of 89.1% in acetonitrile and to p-phenylenediamine (p-PDA) of 85.0% yield in water. This work demonstrates a vital strategy to utilize the full economic potential of photogenerated charge carriers and the decisive role of solvent for product selectivity in the course of selective organic transformations.

Study on the photoelectrocatalytic activity of reduced TiO2 nanotube films for removal of methyl orange

Abstract The reduced TiO2 film on which a photoelectrocatalytic (PEC) process had occurred was created from TiO2 nanotube film electrodes by the electrochemical reduction method. The obtained samples’ structure and morphology were characterized using UV-Vis diffuse reflectance spectroscopy, scanning electron microscopy, high-resolution transmission electron microscopy, photoluminescence, and X-ray diffraction. Cyclic voltammetry, linear sweep voltammetry, electrochemical impedance spectroscopy, chronoamperometry, UV-Vis absorbance spectroscopy, and Mott–Schottky plots were employed to examine the electrochemical and photoelectrochemical activities of the prepared electrodes. The results showed that the optimal conditions of cathodic polarization were a potential of −1.4 V for 60 min. The reduced TiO2 nanotube film electrode had better photoelectrochemical activities than pristine TiO2 under UV light due to the higher photocurrent density (13.7 mA‧cm−2) at 1.5 V (vs Ag/AgCl, sat. KCl reference electrode) compared to pristine TiO2 achieving 7.3 mA‧cm−2, indicating more effective charge separation and transport. The degradation of methyl orange (MO) on pristine TiO2 and reduced TiO2 electrodes was carried out in electrocatalytic (EC) and PEC conditions. The PEC process on the reduced TiO2 electrode had the highest MO processing efficiency (98.4%), and the EC process for MO removal on reduced TiO2 had higher efficiency (95.1%) than the PEC process on pristine TiO2 (89.2%).

Boosting photocatalytic dehydrogenation and simultaneous selective oxidation of benzyl alcohol to benzaldehyde over flower-like MoS2 modified Zn0.5Cd0.5S solid solution

A series of MoS2/Zn0.5Cd0.5S with varying concentrations of flower-like MoS2 is prepared based on a simple and practical method with highly efficient photocatalytic dehydrogenation and simultaneous selective oxidation of benzyl alcohol (BA) to benzaldehyde (BAD). A comparative study between the composites and their two components (pristine MoS2 and Zn0.5Cd0.5S) is carried out for various structural, optical, electrical, and photocatalytic characterization. The studies reveal that the size of Zn0.5Cd0.5S nanoparticles is in the order of 3∼5 nm and is distributed uniformly over the surface of the flower-like 350 nm sized MoS2. The optical research conducted using UV–vis diffuse reflectance spectroscopy reflecting an excellent photoresponse by the MoS2/Zn0.5Cd0.5S. The photoelectrochemical tests showed that the adding of proper ratio of flower-like MoS2 (6%) results in an efficient separation and migration of photogenerated carriers for pristine Zn0.5Cd0.5S nanoparticles. The photocatalytic dehydrogenation rate of BA for the 6%-MoS2/Zn0.5Cd0.5S is the highest at 3.03 mmol g−1 h−1, meanwhile the yield of BAD and the selective conversion of BA to BAD are 49.3% and 100%, respectively. The essential stages of the photocatalytic dehydrogenation of BA are ·C caused by the photo-generated holes, according to the EPR spectra of the PBN-carbon centered radical (PBN–C). Besides, the mechanism for improved photocatalytic dehydrogenation and synergistic selective oxidation of BA to BAD with flower-like MoS2 modified Zn0.5Cd0.5S nanoparticles was systematically studied through gas chromatography-mass spectrometry analysis and first principle density functional theory calculations. The highly efficient dehydrogenation and synergistic selective oxidation of BA to BAD for MoS2/Zn0.5Cd0.5S are mainly attributed to the introduction of MoS2 nanoflowers that can provide abundant active sites, and formed MoS2/Zn0.5Cd0.5S heterostructures could further promote the separation of photogenerated electron-hole pairs. Moreover, the valance band position of the 6%-MoS2/Zn0.5Cd0.5S is more positive, so the hole at the VB position has the stronger ability to oxidize BA. This study provides a feasible method for efficiently photocatalytic dehydrogenation synergism selective oxidation of organic substrates into valuable products.

Silica-magnesium-titanium Ziegler-Natta catalysts. Part 1: Structure of the pre-catalyst at a molecular level

In this paper, which is the first part of a more extended work, we elucidate the molecular level structure of a highly active SiO2-supported Ziegler-Natta precatalyst obtained by reacting a dehydroxylated silica and a solution of an organomagnesium compound with TiCl4. The synergetic combination of Ti K-edge and Ti L3-edge X-ray Absorption spectroscopy (XAS) and diffuse reflectance UV–Vis spectroscopies, complemented by Density Functional Theory (DFT) simulations, indicate that small TiCl3 clusters similar to β-TiCl3 coexist with isolated monomeric Ti(IV) species. Ti K-edge Extended X-ray Absorption Fine Structure (EXAFS) Spectroscopy allows the quantification of these two phases and demonstrates that the Ti(IV) sites are 6-fold coordinated (either by six chlorine ligands or by five chlorine and one oxygen ligands), but highly distorted, similar to what is modelled for TiCl4-capped MgCl2 nanoplatelets. Finally, IR spectroscopy suggests that the MgCl2 phase has a molecular character (Far-IR) and that the only accessible Mg2+ sites are uncoordinated cations acting as Lewis acid sites (IR of CO adsorbed at 100 K). Based on these experimental findings, we propose the co-existence in the precatalyst of small TiCl3 clusters and of mixed oxo-chloride magnesium-titanium structures deposited at the silica surface. The evolution of the precatalyst in the presence of the activator and of the monomer is discussed in the second part of this work.