Simple Co-precipitation Method Research Articles

Degradation of cefadroxil drug by newly designed solar light responsive alcoholic template-based lanthanum ferrite nanoparticles

In this work, lanthanum ferrite nanoparticles were synthesized via a simple co-precipitation method. Two different templates, namely sorbitol and mannitol, were used in this synthesis to tune the optical, structural, morphological, and photocatalytic properties of lanthanum ferrite. The synthesized lanthanum ferrite-sorbitol (LFOCo-So) and lanthanum ferrite-mannitol (LFOCo-Mo) were investigated through Ultraviolet–Visible (UV–Vis), X-ray diffraction (XRD), Fourier Transform Infra-Red (FTIR), Raman, Scanning Electron Microscopy-Energy Dispersive X-ray (SEM-EDX), and photoluminescence (PL) techniques to study the effects of the templates on the tunable properties of lanthanum ferrite nanoparticles. The UV–Vis study revealed a remarkably small bandgap (2.09 eV) of LFOCo-So compared to the LFOCo-Mo having a band gap of 2.46 eV. XRD analysis revealed a single-phased structure of LFOCo-So, whereas LFOCo-Mo showed different phases. The calculated crystallite sizes of LFOCo-So and LFOCo-Mo were 22 nm and 39 nm, respectively. FTIR spectroscopy indicated the characteristics of metal-oxygen vibrations of perovskites in both lanthanum ferrite (LFO) nanoparticles, whereas a slight shifting of Raman scattering modes in LFOCo-Mo in contrast to LFOCo-So showed the octahedral distortion of the perovskite by changing the template. SEM micrographs indicated porous particles of lanthanum ferrite with LFOCo-So being more uniformly distributed, and EDX confirmed the stoichiometric ratios of the lanthanum, iron, and oxygen in the fabricated lanthanum ferrite. The high-intensity green emission in the photoluminescence spectrum of LFOCo-So indicated more prominent oxygen vacancies than LFOCo-Mo. The photocatalytic efficiency of synthesized LFOCo-So and LFOCo-Mo was investigated against cefadroxil drug under solar light irradiation. At optimized photocatalytic conditions, LFOCo-So showed higher degradation efficiency of 87% in only 20 min than LFOCo-Mo having photocatalytic activity of 81%. The excellent recyclability of the LFOCo-So reflected that it could be reused without affecting photocatalytic efficiency. These findings showed that sorbitol is a useful template for the lanthanum ferrite particles imparting outstanding features, enabling it to be used as an efficient photocatalyst for environmental remediation.

A response surface modeling and optimization of photocatalytic degradation of 2,4-dichlorophenol in water using hierarchical nano-assemblages of CuBi2O4 particles.

Photocatalytic degradation, as an advanced oxidation process (AOPs), offers a great advantage to target persistent organic pollutants (POPs) in water. RSM in the present study which is statistical means for optimizing processes like photocatalysis with minimum laboratory experimentation. RSM has a history of being a potent design experiment tool for creating new processes, modifying their designs, and optimizing their performances. Herein, a highly sought-after, easily preparable, visible-light active, copper bismuth oxide (CuBi2O4) is applied against a toxic emerging contaminant, 2,4-dichlorophenol (2,4-DCP) under an LED light source (viible light λ > 420nm). A simple coprecipitation method was adopted to synthesize CuBi2O4 and later analyzed with FESEM, EDX, XRD, FTIR, and spectroscopy to determine its intrinsic properties. Principally, the photocatalytic degradation investigations were based on response surface methodology (RSM), which is a commanding tool in the optimization of the processes. The 2,4-DCP concentration (pollutant loading), CuBi2O4 dosage (catalyst dosge), contact time, and pH were the chosen as dependent factors, that were optimized. However, under optimal conditions, the CuBi2O4 nanoparticle showed a remarkable photocatalytic performance of 91.6% at pH = 11.0 with a pollutant concentration of 0.5mg/L and a catalyst dose of 5mg/L within 8h. The obtained RSM model showed a satisfactory correlation between experimental and predicted values of 2,4-DCP removal, with an agreeable probability value (p) of 0.0069 and coefficient of regression (R2) of 0.990. It is therefore anticipated that the study may open up new possibilities for formulating a plan to specifically target these organic pollutants. In addition, CuBi2O4 possessed fair reusability for three-consequent cycles. Hence, the as-synthesized nanoparticles applied for photocatalysis foster a fit-for-purpose and reliable system in the decontamination of 2,4 DCP in environmental samples, and also the study highlights the efficient use of RSM for environmental remediation, particularly in AOP implementation.

Schiff-base ligand assisted synthesis of DyVO4/AgBr nanocomposites, characterization, and investigation of photocatalytic activity over organic dye contaminants

In the current study, a type-I DyVO4/AgBr heterojunction was prepared by a simple and cost-effective co-precipitation method to obtain a highly efficient photocatalyst for water treatment. The effect of different molar ratios of H2Salen to dysprosium and temperature reaction was studied on the morphology of the products. As a result of the energy savings, the optimal temperature for the preparation of DyVO4 nanoparticles was chosen as 25 °C, and DyVO4/AgBr nanocomposites were prepared at this temperature. The XRD results revealed that DyVO4 and DyVO4/AgBr nanocomposites were pure in all conditions. A comparative study was conducted between the photocatalytic behavior of DyVO4, AgBr, and DyVO4/AgBr under UV and visible radiation. The photodegradation result reveals that DyVO4/AgBr performs better than pure DyVO4 and AgBr. 79.8% and 72.0% of methylene blue (MB) were degraded by DyVO4/AgBr nanocomposites under UV and visible light after 90 min, respectively. The kinetics study depicts that the higher reaction constant rate (k = 0.0187 min−1) belongs to DyVO4/AgBr nanocomposite that has the maximum photodegradation.

Performance and Mechanism of Functionalized Water Hyacinth Biochar for Adsorption and Removal of Benzotriazole and Lead in Water.

In this paper, water hyacinth is used to prepare biochar (WBC). A biochar-aluminum-zinc-layered double hydroxide composite functional material (WL) is synthesized via a simple co-precipitation method which is used to adsorb and remove benzotriazole (BTA) and lead (Pb2+) in an aqueous solution. In particular, this research paper uses various characterization methods to analyze WL and to explore the adsorption performance and adsorption mechanism of WL on BTA and Pb2+ in an aqueous solution through batch adsorption experiments combined with model fitting and spectroscopy techniques. The results indicate that the surface of WL contains a thick sheet-like structure with many wrinkles which would provide many adsorption sites for pollutants. At room temperature (25 °C), the maximum adsorption capacities of WL on BTA and Pb2+ are 248.44 mg·g-1 and 227.13 mg·g-1, respectively. In a binary system, during the process of using WL to adsorb BTA and Pb2+, compared with that in the absorption on Pb2+, WL shows a stronger affinity in the adsorption on BTA, and BTA would thus be preferred in the absorption process. The adsorption process of WL on BTA and Pb2+ is spontaneous and is endothermic monolayer chemisorption. In addition, the adsorption of WL on BTA and Pb2+ involves many mechanisms, but the main adsorption mechanisms are different. Among them, hydrogen bonding dominates the adsorption on BTA, while functional groups (C-O and C=O) complexation dominates the adsorption on Pb2+. When WL adsorbs BTA and Pb2+, the coexistence of cations (K+, Na+, and Ca2+) has a strong anti-interference ability, and WL can use a lower concentration of fulvic acid (FA) (<20 mg·L-1) to improve its adsorption performance. Last but not least, WL has a stable regenerative performance in a one-component system and a binary system, which indicates that WL has excellent potential for the remediation of BTA and Pb2+ in water.

One-Step Synthesis of Ag2O/Fe3O4 Magnetic Photocatalyst for Efficient Organic Pollutant Removal via Wide-Spectral-Response Photocatalysis-Fenton Coupling.

Photocatalysis holds great promise for addressing water pollution caused by organic dyes, and the development of Ag2O/Fe3O4 aims to overcome the challenges of slow degradation efficiency and difficult recovery of photocatalysts. In this study, we present a novel, environmentally friendly Ag2O/Fe3O4 magnetic nanocomposite synthesized via a simple coprecipitation method, which not only constructs a type II heterojunction but also successfully couples photocatalysis and Fenton reaction, enhancing the broad-spectrum response and efficiency. The Ag2O/Fe3O4 (10%) nanocomposite demonstrates exceptional degradation performance toward organic dyes, achieving 99.5% degradation of 10 mg/L methyl orange (MO) within 15 min under visible light irradiation and proving its wide applicability by efficiently degrading various dyes while maintaining high stability over multiple testing cycles. Magnetic testing further highlighted the ease of Ag2O/Fe3O4 (10%) recovery using magnetic force. This innovative approach offers a promising strategy for constructing high-performance photocatalytic systems for addressing water pollution caused by organic dyes.

Nickel molybdate/cobalt molybdate nanoflakes by one-pot synthesis approach for electrochemical detection of antipsychotic drug chlorpromazine in biological and environmental samples

Pharmaceutical waste products have become environmental contamination and pollution which poses a significant risk to our planet. The fabrication of effective antipsychotic drug monitoring systems is greatly important to minimize their environmental problems. Therefore, the construction of mixed metal molybdates has been investigated to develop an electrochemical sensor with high sensitivity and low detection limits. In regards, we have successively synthesized nickel molybdate/cobalt molybdate (NiMoO4/CoMoO4; NCMO) through a simple co-precipitation method and their electrocatalytic activity of chlorpromazine (CPZ) evaluated. The synthesized NCMO was inspected by diverse physicochemical analyses. From the morphological study, the prepared NCMO nanoflake displays exceptionally rich surface electroactive sites. Furthermore, the electrochemical properties of the developed sensor were investigated through cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and differential pulse voltammetry (DPV). Accordingly, the NCMO endorses greater electrochemical behavior because of rapid electron transfer, improved electrochemical active surface area, and synergetic effect. The established electrochemical sensor displays a wide linear range and the lowest detection limit, admirable sensitivity, reproducibility, and repeatability. Finally, the real-time application of CPZ was performed in wastewater and human urine samples with reasonable recoveries.

Magnetic coffee residue biosorbent for selective extraction of zinc oxide nanoparticles in water samples

ABSTRACT. Quantification of engineered nanomaterials in the environment has attracted researchers’ interest recently because of their increased release to the environment. In this study, a recyclable and easily accessible magnetized coffee residue (MCR) is proposed for magnetic solid-phase extraction (MSPE) of zinc oxide nanoparticles (ZnO-NPs) from water samples. The MCR was synthesized using a simple one-step chemical co-precipitation method from coffee residue and was characterized by state-of-the-art techniques. Various parameters affecting the MSPE efficiency of ZnO-NPs were optimized and 8.5 pH, 75 mg adsorbent, 120 min extraction time, 10 mL sample volume, 4 mL of 0.001 M HCl as an eluting solvent, and 30 min elution time were identified as the optimum conditions. Under these conditions, the method showed excellent linearity (R2 = 0.995) and good sensitivity (detection limit, 0.12 mg L-1, and quantification limit, 0.4 mg L-1). Intra and inter-day percent standard deviations were 1.4 and 2.2%, respectively, for the analysis of 6 mg L-1 ZnO-NPs. The practical applicability of the method for the extraction of ZnO-NPs in environmental samples was evaluated, and recovery values in the range of 93.0–98.2% were obtained, confirming its successful performance. Generally, the technique is easy, economical, and eco-friendly that can be considered for the extraction of metal oxide nanoparticles.&#x0D; &#x0D; KEY WORDS: Zinc oxide nanoparticles, Magnetic coffee residue, Magnetic solid-phase extraction, Flame atomic absorption spectroscopy, Environmental waters&#x0D; &#x0D; Bull. Chem. Soc. Ethiop. 2023, 37(4), 859-873. &#x0D; DOI: https://dx.doi.org/10.4314/bcse.v37i4.5

Mechanistic study of nitrogen-modified titanium dioxide nanoparticles for enhancing the degradation of organic dyes and antibacterial properties under visible-light irradiation

Titanium oxide sulfate, the raw material for one of the industrial preparation methods of titanium dioxide (TiO2), and urea as the nitrogen source were used to synthesize N-modified TiO2 materials (N-TiO2) with different chemical bonding of N elements by a relatively simple homogeneous co-precipitation method, providing a theoretical basis and experimental foundation for the industrial preparation of N-TiO2 photocatalytic materials. According to the analysis of its microscopic morphology, structural composition, and optoelectronic properties, the material consisted of porous spherical clusters formed by the aggregation of spherical nanoparticles. Nitrogen atoms were uniformly distributed on the surface of the material, causing a red shift in its optical response range and a reduction in the electron-hole recombination rate, which contributed to the photocatalytic performance of the material. The conducted photocatalytic degradation experiments of methyl orange and rhodamine B revealed that both dyes can be effectively degraded under visible-light conditions. Methyl orange interacted with the oxygen vacancies and Brønsted acid sites on the surface of the material, converting from an azo structure to a more degradable quinoid structure. In antibacterial experiments, N-TiO2 demonstrated excellent antibacterial properties, which led to a preliminary discussion of its antibacterial mechanism. According to electron paramagnetic resonance investigations and reactive oxygen species (ROS) scavenging experiments, the material can generate multiple ROS at the same time, among which·OH is the key active substance.

Evaluation of synergistic approach of spinel cadmium–copper nanoferrites as magnetic catalysts for promoting wastewater decontamination: Impact of Ag ions doping

Metal substitution is an efficient strategy to improve the catalytic activity of ferrite-based catalysts. In this study, Cd0.5Cu0.5−xAgxFe2O4 (where 0 ≤ x ≤ 0.5) ferrites were fabricated via a simple co-precipitation method. The influence of the silver ions on the structural, magnetic, and catalytic characteristics of the spinel nanoparticles, as well as on their morphology, was examined. X-ray diffractograms revealed a crystalline cubic spinel structure with crystallite sizes in the nanoregime (7–15 nm). The saturation magnetization reduced from 29.8 to 2.80 emu as the Ag+ doping increased. Two prominent absorption bands were visible in Fourier-transform infrared spectra at 600 cm−1 and 400 cm−1, respectively, and they belonged to the tetrahedral (A) and octahedral (B) sites. The samples were then used as catalysts for the oxidative breakdown of the typical organic contaminant indigo carmine dye (IC). The catalytic process followed the first-order kinetic model, and the rate constant increased from 0.007 to 0.023 min−1 with increasing of Ag+ doping. Cd0.5Cu0.5-xAgxFe2O4 exhibited excellent catalytic performance in the pH range of 2–11, which means that they are promising efficient and stable materials for Fenton-based alkaline wastewater treatment. Finally, the pathway includes, HO•, HO2−•, and O2−• as oxidants resulted from the synergistic effects of Fe3+, Cu2+, and Ag+, with H2O2 and surface hydroxyl groups have been proposed.Graphical

Amorphization of nanostructured prussian blue analogues for boosting oxygen evolution reaction toward design of efficient electrocatalysts

Facile incorporation of crystal defects or creating amorphous phase into crystalline functional materials can significantly alter their characteristics leading to boost new technological advances and applications. Herein, nickel hexacyanoferrate (NiHCF) nanoparticles (NPs) and its derivatives synthesized by a simple co-precipitation method, and thermally cured in nitrogen and air atmospheres. The formed cubic nickel-iron framework crystals and their derivatives explored for oxygen evolution reaction (OER) via modification of a glassy carbon electrode (GCE). Expressively, thermal curing of NiHCF in nitrogen and air create variable crystal defects leading to control amorphization at reasonably high temperatures. The NiHCF nanocrystals show overpotentials (η10) of 330 mV for OER at GC/N300 (NiHCF treated at 300 °C in N2) in alkaline medium. Fascinatingly, the results explored the synergistic action for iron/nickel sites and their oxidation states in the NiHCF crystals for OER with superior stability for more than 10 h.

Engineering of a Hybrid g-C3N4/ZnO-W/Cox Heterojunction Photocatalyst for the Removal of Methylene Blue Dye

Robust hybrid g-C3N4/ZnO-W/Cox heterojunction composites were synthesized using graphitic carbon nitride (g-C3N4) and ZnO-W nanoparticles (NPs) and different concentrations of Co dopant. The hybrid heterojunction composites were prepared by simple and low-cost coprecipitation methods. The fabricated catalyst was explored and investigated using various characterization techniques such as FTIR, XRD, FESEM and EDX. The surface morphology of the as-prepared hybrid nanocomposites with particle sizes in the range of 15–16 nm was validated by SEM analysis. The elemental composition of the synthesized composites was confirmed by EDS analysis. Photocatalysis using a photon as the sole energy source is considered a challenging approach for organic transformations under ambient conditions. The photocatalytic activity of the heterojunctions was tested by photodegrading methylene blue (MB) dye in the presence of sunlight. The reduced band gap of the heterojunction composite of 3.22–2.28 eV revealed that the incorporation of metal ions played an imperative role in modulating the light absorption range for photocatalytic applications. The as-synthesized g-C3N4/ZnO-W/Co0.010 composite suppressed the charge recombination ability during the photocatalytic degradation of methylene blue (MB) dye. The ternary heterojunction C3N4/ZnO-W/Co0.010 composite showed an impressive photocatalytic performance with 90% degradation of MB under visible light within 90 min of irradiation, compared to the outcomes achieved with the other compositions. Lastly, the synthesized composites showed good recyclability and mechanical stability over five cycles, confirming them as promising photocatalyst options in the future.

Enhanced Optical Nonlinearity in Bi3+-Doped CePO4 Nanostructures for Optical Limiting Applications

Pure and Bi3+-doped CePO4 were synthesized by the simple co-precipitation method. Successful dopant incorporation into the host lattice of orthophosphate without altering the crystalline structure was confirmed by structure analysis, X-ray diffraction, and Raman characterization. Morphological investigation was done using HR-SEM which portrays the co-existence of nanospheres and nanorods in doped CePO4 and only nanospheres in pure CePO4. X-ray photoelectron spectroscopy studies confirm the +3 oxidation state of Ce3+ and Bi3+ with the presence of a trace amount of Ce4+ in the as-prepared nanoparticles. Vibration sample magnetometer studies show weak ferromagnetic behavior of the nanostructures at room temperature. The absorption band in the wavelength range 200–300 nm accounts for 4f–5d electronic transition, and a red shift in the band edge is due to the increase in the band gap with the addition of the dopant. Photoluminescence emission spectra show broad blue-green emission owing to transition of Ce3+ from the excited state to the ground state and also due to oxygen vacancy. The nonlinear optical absorption and optical limiting (OL) behaviors of Bi3+-doped cerium orthophosphate (CePO4) were investigated using an open-aperture (OA) Z-scan technique under an excitation source of 532 nm nanopulsed lasers. The recorded OA transmittance curve reveals a transition from saturable absorption to reverse saturable absorption in pure CePO4 at 2.46 GW/m2, whereas all the doped samples exhibit RSA attributed to 2PA. The increase in the nonlinear absorption (NLA) coefficient with on-axis intensity and the availability of the near resonant energy state due to the Bi3+ dopant ensure the sequential 2PA (1PA + ESA) phenomenon. Compared to pure CePO4, doped nanostructures show improved NLA coefficients due to the availability of the defect state and oxygen vacancies in Bi3+-doped CePO4. Interestingly, a lower OL threshold (OLT) of 0.14 × 10–13 W/m2 is observed in 0.3% Bi3+-doped CePO4. The lower OLT value of Bi3+-doped CePO4 ensures its potential candidature for OL applications in protecting optical sensors and human eyes.

Simple Co-Precipitation of Iron Minerals for the Removal of Phenylarsonic Acid: Insights into the Adsorption Performance and Mechanism.

In this study, three kinds of iron minerals, ferrihydrite, hematite, and goethite, were prepared by a simple coprecipitation method for the adsorption and removal of phenylarsonic acid (PAA). The adsorption of PAA was explored, and the influences of ambient temperature, pH, and co-existing anions on adsorption were evaluated. The experimental results show that rapid adsorption of PAA occurs within 180 min in the presence of iron minerals, and the adsorption process conforms to a pseudo-second-order kinetic model. The isothermal adsorption of PAA by ferrihydrite, goethite, and hematite agrees with the Redlich-Peterson model. The maximum adsorption capacities of PAA are 63.44 mg/g, 19.03 mg/g, and 26.27 mg/g for ferrihydrite, goethite, and hematite, respectively. Environmental factor experiments illustrated that an alkaline environment will significantly inhibit the adsorption of PAA by iron minerals. CO32-, SiO32-, and PO43- in the environment will also significantly reduce the adsorption performance of the three iron minerals. The adsorption mechanism was analyzed by FTIR and XPS, which indicated that ligand exchange between the surface hydroxyl group and the arsine group leads to the formation of an Fe-O-As bond, and electrostatic attraction between the iron minerals and PAA played an important role in the adsorption.

Adsorption of 2,4-dichlorophenoxyacetic acid and glyphosate from water by Fe3O4-UiO-66-NH2 obtained in a simple green way

In this study, a green adsorbent (Fe3O4-UiO-66-NH2) with the ability of addressing the issues of separation and recovery of UiO-66-NH2 is obtained using a simple co-precipitation method under environmentally benign conditions. Various characterization techniques are utilized for evaluating the properties of the developed adsorbent. The capability of Fe3O4-UiO-66-NH2 towards 2,4-dichlorophenoxyacetic acid (2,4-D) and glyphosate (GP) from solution is explored. The results revealed that the magnetization process did not destroy the crystal structure of UiO-66-NH2, which ensured that Fe3O4-UiO-66-NH2 had good adsorption performance for 2,4-D and GP. The adsorption processes showed a wide pH application range, high salt tolerance, and regeneration performance as well as an excellent adsorption rate. Results from thermodynamic study showed that both processes were spontaneous and endothermic. The unit uptake ability of Fe3O4-UiO-66-NH2 for 2,4-D and GP reached up to 249mg·g-1 and 183mg·g-1 from Langmuir model at 303K, respectively. When solid-liquid ratio was 2g·L-1, Fe3O4-UiO-66-NH2 can reduce the content of 2,4-D or GP with the initial density of 100mg·L-1 below the drinking water requirement limit. In addition, the reusability efficiency of Fe3O4-UiO-66-NH2 towards 2,4-D and GP was found to be 86% and 80% using 5mmol·L-1 NaOH as eluent. Analysis of simulated water samples indicated that Fe3O4-UiO-66-NH2 could achieve the single or simultaneous removal of 2,4-D and GP from wastewater. Summarily, Fe3O4-UiO-66-NH2 as a green adsorbent can serve as an alternative for removing 2,4-D and GP from water body.

Catalytic ozonation of N-methyldiethanolamine over mixed oxides derived from Mg/Fe-LDH.

The aim of this study was to evaluate the efficiency of catalytic ozonation to increase the degradation of aqueous N-methyldiethanolamine (MDEA) solutions, using two lamellar double hydroxides, namely MgxFe-LDH with x = Mg/Fe = 2, 3, were synthesized by the simple and rapid co-precipitation method. Then, the obtained materials were calcined at 400 °C for 6 h. The calcined products were respectively designated as HTcMg2Fe and HTcMg3Fe, and characterized by powder X-ray diffraction (XRD), N2 physisorption (BET), Fourier transform infrared spectra (FT-IR), and scanning electron microscopy (SEM). The powders produced were used in the ozonation reaction to remove MDEA from aqueous solutions. Experimental results showed that the highest MDEA removal efficiency is in the catalytic ozonation process. Under the optimal conditions for heterogeneous catalytic ozonation of MDEA: initial concentration of 4 Wt% MDEA, 30 °C, catalyst mass of 30 mg/100 ml solution, and contact time of 60 min. The results showed the highest percentage of COD removal, which was up to 80.76% for HTcMg2Fe higher than that of HTcMg3Fe 80.36%.

Structural, optical and magnetic properties of Y-doped NiFe2O4 nanoparticles prepared by simple co-precipitation method

Structural, optical and magnetic properties of Y-doped NiFe2O4 nanoparticles prepared by simple co-precipitation method

Disclosing the nature of vacancy defects in α-Ag2WO4

Defects at semiconductors with electron acceptor and donor sites govern the electronic and optoelectronic applications due to their unique electronic properties. This work provides deep insight into the nature of defects and the conduction mechanism in α-Ag2WO4. To this aim, a detailed analysis of the results of XRD with Rietveld refinements, FE-SEM images, and measurements of different spectroscopies (impedance, positron annihilation lifetime, and photoluminescence) are carried out on α-Ag2WO4 samples synthesized by a simple co-precipitation method. Two types of vacancy defects: cationic O-vacancies, and anionic Ag or Ag–O vacancy complexes are elucidated with a Schottky p-type potential barrier. The results indicate that the Ag vacancies remain constant during thermal treatment, while an opposite effect is found for the oxygen vacancies. This behavior governs the multifunctional properties of α-Ag2WO4 semiconductors via a tunneling plus thermionic conduction mechanism.

Modulating the Electronic Structure of α-Fe2O3 by Doping Atomically Dispersed Ce for the Transfer Hydrogenation of Nitroaromatics Using Stoichiometric Hydrazine Hydrate

The metal-oxide-catalyzed transfer hydrogenation of nitroarenes to anilines by hydrazine hydrate has been widely reported; however, the risk of explosion resulting from excess hydrazine hydrate and high temperatures and complex preparations of these catalysts immensely hinder their industrial application. Herein, we use a simple co-precipitation method to synthesize atomically dispersed Ce-doped α-Fe2O3 (Ce0.025-Fe2O3-350 °C), which can completely reduce nitroarenes using stoichiometric hydrazine hydrate at room temperature, where the parent α-Fe2O3 is inactive. A thorough characterization indicates that the incorporation of Ce into the crystal lattice of α-Fe2O3 reorganizes the electronic structure of the surrounding Fe, such that the Lewis acidity of Fe2O3 is enhanced, which is the key for the room-temperature decomposition of N2H4·H2O. The structure is also beneficial for the adsorption of nitroarene, leading to the weakening of the N–O bonds. Mechanistic experiments and DFT calculations demonstrate that the reduction proceeds through Ph-NO2 → Ph-NHOH → Ph-NH2 without the widely recognized Ph-NO intermediate. Moreover, Ce0.025-Fe2O3-350 °C exhibits good stability in a continuous-flow reaction.

Enhanced low-temperature activity and huimid-SO2 resistance of MnFe-based multi-oxide catalysts for the marine NH3-SCR reaction

Several MnFe-based multi-metal oxides were synthesized as NH3-SCR catalysts by a simple coprecipitation method for abating NOx of marine diesel exhausts. The Co and Nb-doped MnFeCeAl catalysts exhibit NOx conversion over 90% and N2 selectivity above 95% at 180–270 °C, especially the MnFeCeAlCo catalysts can inhibit nearly all sulfate species growth within 150 ppm humid-SO2 gases at 225 °C. The structural characterization results revealed that Co, Nb, Sm, and Sb doping can enhance interactions among different components and promote active component dispersion. Temperature programmed analysis indicated that the Co doping is not only more favorable for improving redox properties, but can also enhance the surface acidity, which are advantageous to improve the activity, N2 selectivity, and humid-SO2 resistance. Moreover, the XPS results implied that the binding energy shift or the valence variation of the Sm, Sb, Nb, and Co species on catalyst surfaces are favored to raise the atomic ratios of high-valent Mn species and surface adsorbed oxygen, which can promote the redox property significantly and further facilitate SCR activity. Accordingly, the excellent activity and humid-SO2 tolerance of the MnFeCeAlCo catalyst should attribute to its lower redox temperature, strong interaction between oxides, 47.3% surface Mn4+/Mn3+ species, and 71.8% adsorbed oxygen, which provide a method for improving the SCR performances of MnFe-based catalysts with humid SO2 resistance.

Transition metal nanoparticles composite Al(OH)3 catalysts for hydrogen generation of Al/H2O system

BackgroundEnhanced reaction of Al and water through catalysts is an excellent method for hydrogen generation. The generation of hydrogen is closely connected to the activity of catalysts. MethodsThis work prepares a highly active metal-composite aluminum hydroxide (MCAH) catalyst by a simple co-precipitation method. The metallic nanoparticles are Ni, Co, and Ag. The MCAH catalyst exhibits a robust catalytic effect and significantly promotes the reaction of Al and water by decreasing the induction time. Characterization using powder X-ray diffraction, field emission scanning electron microscopy (FESEM), and Brunauer–Emmett–Teller (BET) adsorption analysis show that the metallic nanoparticles are attached to the surface of aluminum hydroxide, increasing the catalytic activity, which is considered to be assistant to the generation of hydrogen. Significant findingsThe high catalytic activity could be due to the high specific surface area (such as Ni-Al(OH)3 for 144.1 m2/g) and stability. Furthermore, the dissociation of water molecules on the surface of the catalyst and the micro galvanic interaction between the metals and the Al(OH)3 could promote the hydration of the passive oxide layer on the surface of Al particles. Therefore, accelerate hydrogen generation.