Template-free Synthesis Research Articles

Template-free Synthesis of Stable Cobalt Manganese Spinel Hollow Nanostructured Catalysts for Highly Water-Resistant CO Oxidation.

SummaryDevelopment of spinel oxides as low-cost and high-efficiency catalysts is highly desirable; however, rational synthesis of efficient and stable spinel systems with precisely controlled structure and components remains challenging. We demonstrate the design of complex nanostructured cobalt-based bimetallic spinel catalysts for low-temperature CO oxidation by a simple template-free method. The self-assembled multi-shelled mesoporous spinel nanostructures provide high surface area (203.5 m2/g) and favorable unique surface chemistry for producing abundant active sites and lead to the creation of robust microsphere configured by 16-nm spinel nanosheets, which achieve satisfactory water-resisting property and catalytic activity. Theoretical models show that O vacancies at exposed {110} facets in cubic spinel phase guarantee the strong adsorption of reactive oxygen species on the surface of catalysts and play a key role in the prevention of deactivation under moisture-rich conditions. The design concept with architecture and composition control can be extended to other mixed transition metal oxide compositions.

Template-free synthesis of LiV3O8 hollow microspheres as positive electrode for Li-ion batteries

The development of hierarchical micro-/nanostructures has received great attention in the field of electrochemical energy storage and conversion. In this report, we demonstrate a template-free synthesis of LiV3O8 hollow microspheres from vanadium ethylene glycolate intermediate, which in turn was obtained by a facile solvothermal route. Evaluation of morphological features with FE-SEM and HR-TEM shows hollow spheres of size 1.8 ± 0.1 µm diameters with wall thickness and void size of 200 ± 20 nm and 1.5 ± 0.1 µm, respectively. Powder X-ray diffraction confirms that both the intermediate and LiV3O8 hollow spheres are highly crystalline without any impurity phase. Tested as a positive electrode in lithium-ion batteries, the LiV3O8 hollow spheres constructed electrode shows a discharge capacity of 304 mAh g−1 at 0.1 C rate and 246 mAh g−1 at 1 C rate during the first discharge. More importantly, LiV3O8 electrode delivers stable cycle-life performance with a specific capacity of 156 mAh g−1 after 300 (dis)charges at 1 C rate. The present hollow LiV3O8 structures would be expected to offer additional active sites, void space to counter volume expansion, and thin-shell structures to provide shortest path for Li+ ion/electron transport, thereby enhancing the cycling stability and rate performance.

Template free synthesis of hierarchical porous zeolite Beta with natural kaolin clay as alumina source

Abstract A template free synthesis route was developed for the synthesis of hierarchical zeolite Beta from a natural layered aluminosilicate mineral kaolin. Detailed study on the crystallization of zeolite Beta established the optimized synthesis condition, and the synthesized hierarchical Beta zeolite was fully studied by XRD, IR, SEM, TEM, BET, NH3-TPD, Py-IR and NMR techniques. The characterization results reveal that the hierarchical Beta zeolite possesses good crystallinity, bimodal pore architecture, large surface area, big pore volume, high acid site concentration and excellent hydrothermal stability. An improved catalytic performance was achieved in hierarchical Beta zeolite for the esterification of acetic acid with benzyl alcohol, and the high activity and selectivity in this zeolite are mainly attributed to the presence of mesopores for accelerating the intraparticle diffusion rate of both reactant and product. This novel synthesis methodology provides a low-cost and environmentally-benign way for the preparation of hierarchical Beta zeolite, which could serve a sustainable platform of large-scale production of hierarchical zeolite for practical application.

Template-free synthesis of biomass-derived hierarchically mesoporous carbon with ultra-small FeNi nanoparticles for oxygen evolution reaction

Highly active and stable catalysts towards electrochemical oxygen evolution reaction are crucial for efficient water splitting and sustainable hydrogen generation. Here we report a carbon supported FeNi catalyst synthesized from an in situ freeze-drying method (fd-FeNi/C) with a commonly seen biomass, jasminum mesnyi flower. The fd-FeNi/C exhibits a N-doped hierarchically mesoporous carbon structure decorated with small FeNi nanoparticles with a small diameter of ∼ 4 nm. Electrochemical measurements show excellent catalytic performance in 1 M KOH solution with an overpotential of 301 mV at the current density of 10 mA cm−2. The value is 41 mV lower than that of the commercial IrO2/C. A small Tafel slope (64.5 mV dec−1) and high stability are also recorded. This work provides a facile, scalable, and template-free approach to convert biomass into highly active electrochemical catalysts, which shows great potential for future applications.

Template-free synthesis of metallic WS2 hollow microspheres as an anode for the sodium-ion battery

In this work, an electrode has been proposed and designed on its interior structure and controlled morphology, Specifically, metallic WS2 hollow microspheres have been synthesized via a one-step solvothermal process, in the absence of additives, consisting of porous nanosheets with a large surface area. The individual nanosheet features an expanded interlayer distance of 1.02 nm and metallic characteristics, which can provide faster transport of electrons and reduce the diffusion pathway for sodium ions. Furthermore, the effects of anions in the ether-based electrolyte on the cycling performance were also investigated and optimized. As a result, such an anode can demonstrate superior capacitive behavior with excellent rate performance (388.2 mA h g−1 at 0.1 A g−1, 307.7 mA h g−1 at 1 A g−1) and long-term cycling stability (285 mA h g−1 at 2 A g−1 after 2000 cycles).

A novel template-free wet chemical synthesis method for economical production of zinc oxide microrods under atmospheric pressure

This work reports a template-free wet chemical synthesis method for economical production of zinc oxide (ZnO) microrods by using an inexpensive polypropylene beaker as a reactor under atmospheric pressure. The morphology and crystal structure of the as-prepared ZnO microrods were investigated by scanning electron microscopy (SEM), X-ray powder diffraction (XRD) and Raman scattering. Fourier-transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), Ultraviolet–visible (UV/Vis) spectroscopy and methylene blue photocatalytic degradation test were also conducted to study their physical and chemical properties. The results show that the as-prepared ZnO microrods have a hexagonal crystal structure. Under the optimal synthesis condition, they have a diameter of 0.8–2.6 μm and a length of 10–40 μm. Compared with commercial ZnO powders, the as-prepared ZnO microrods have a higher whiteness. Meanwhile, the as-prepared ZnO microrods have very low photocatalytic activity, indicating that they have good photostability and are unlikely to cause the photodegradation of polymers such as binders. As a result, they will be an excellent and economical white pigment with great potential in coating applications.

Synthesis and photoelectrochemical water oxidation of (Y, Cu) codoped α-Fe2O3 nanostructure photoanode

Hematite (α-Fe2O3) is one of the best capable photoanode material for water oxidation under visible light. The role of synergetic effect between two metal dopants for enhanced water oxidation is not adequately studied. The mono-doping (Y) and co-doping (Cu, Y) effect on the crystal structure, morphology, optical properties and their influence as photoanodes for energy harvesting applications are systematically explored. In this study, we have synthesized the pure, mono-doped (Y), and co-doped (Y and Cu) hematite nanostructures for enhanced photoelectrochemical (PEC) performance using a simple template free hydrothermal synthesis technique. The optimized photoelectrode showed a substantial improvement (∼36-times) in the PEC photocurrent density over pristine, mono-doped and co-doped photoanodes. Electrochemical impedance spectroscopy analysis confirmed that the co-dopant enhanced the charge carrier density of hematite and it acts as an electron donor. Moreover, it is demonstrated that the photocurrent density increases after mono-doping from 0.012 mAcm−2 to 0.020 mAcm−2 and further improved to 0.439 mAcm−2 with co-dopant at 1.23 V vs. RHE. The considerably enhanced PEC activity is ascribed to the higher conductivity, enhanced interfacial charge transfer at the surface of hematite and the synergistic effect between two metal dopants.

Scalable and Template-Free Aqueous Synthesis of Zirconium-Based Metal–Organic Framework Coating on Textile Fiber

Organophosphonate-based nerve agents, such as VX, Sarin (GB), and Soman (GD), are among the most toxic chemicals to humankind. Recently, we have shown that Zr-based metal-organic frameworks (Zr-MOFs) can effectively catalyze the hydrolysis of these toxic chemicals for diminishing their toxicity. On the other hand, utilizing these materials in powder form is not practical, and developing scalable and economical processes for integrating these materials onto fibers is crucial for protective gear. Herein, we report a scalable, template-free, and aqueous solution-based synthesis strategy for the production of Zr-MOF-coated textiles. Among all MOF/fiber composites reported to date, the MOF-808/polyester fibers exhibit the highest rates of nerve agent hydrolysis. Moreover, such highly porous fiber composites display significantly higher protection time compared to that of its parent fabric for a mustard gas simulant, 2-chloroethyl ethyl sulfide (CEES). A decreased diffusion rate of toxic chemicals through the MOF layer can provide time needed for the destruction of the harmful species.

Rapid microwave assisted hydrothermal synthesis cerium vanadate nanoparticle and its photocatalytic and antibacterial studies

Catalyst or template-free synthesis of cerium orthovanadate (CeVO4) nanoparticles were synthesized by simple, fast and efficient microwave assisted hydrothermal method using Ce(NO3)3·6H2O and NaVO3 as the starting materials under basic pH condition. The prepared sample was characterized by powder X-ray diffraction (XRD) transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FTIR) and Uv–Visible diffuse reflectance spectroscopy (DRS). Pure tetragonal CeVO4 was successfully synthesized in 10 min of reaction time. The synthesized nanoparticles showed particle sizes in the range 10–20 nm and the optical absorption onset at 456 nm. The optical band gap was calculated to be 2.8 eV. The photocatalytic activity of the synthesized nanoparticles was evaluated by studying the degradation of a model dye, Eosin yellow (EY) under visible irradiation and a feasible mechanism was proposed. More than 89% of EY (60 mg/L) was degraded within 120 min. The antibacterial activity was also evaluated against Gram + ve and Gram -ve microbial pathogens.

Rapid and template-free synthesis of copper(I) oxide-graphitic carbon nitride heterojunction for photocatalytic degradation of orange II dye in water

Herein, we report the synthesis of a p-n heterojunction catalyst comprising Cu2O and g-C3N4 via a novel rapid, template-free and facile one-pot approach. The pristine semiconductors and their composite were characterised by X-ray diffraction (XRD), N2 adsorption-desorption isotherms (BET), UV–vis diffuse reflectance spectroscopy, transmission electron microscopy (TEM), field emission scanning electronic microscopy (FESEM) and energy dispersive X-ray spectrometry (EDX). From the Mott-schottky plot, the flat-band potential and carrier density were estimated. Band gap energies of 2.03 and 2.65 eV were calculated for Cu2O and g-C3N4 respectively, which indicate that both catalysts possess excellent optical absorption in the visible region of the solar spectrum. The p-n heterojunction produced a type-II band alignment which promotes the efficient separation of photogenerated electron-hole pairs. The photocatalytic property of the material was evaluated by employing it for the degradation of orange II dye in water. Different mass ratios of Cu2O-g-C3N4 such as 1:1, 3:2, 7:3 and 9:1 were employed in the degradation process. However, Cu2O-g-C3N4 with mass ratio 9:1 displayed the best photocatalytic performance, giving a removal efficiency that is 3.6 times higher than the pristine Cu2O. The decolourisation and mineralisation efficiencies were 85% and 60% after 4 h of treatment. Scavenger studies further revealed the photogenerated holes as the main oxidant species in the photocatalytic reaction.

Template-free microwave-assisted synthesis of FeTi coordination complex yolk-shell microspheres for superior catalytic removal of arsenic and chemical degradation of methylene blue from polluted water

Yolk-shell FeTi coordination complex microspheres were synthesized using a template-free microwave-assisted hydrothermal method. The influences of hydrothermal reaction time and temperature on the morphology and structure were investigated in details. The FeTi coordination complex microspheres with a yolk-shell structure were tested to be an excellent catalyst to transform As (III) to As (V) as well as an adsorbent to effectively remove As (V) ions from solution with an adsorption capacity as high as 235.3 mg g−1 according to Langmuir adsorption model. The FeTi yolk-shell microspheres presented a rapid chemical degradation towards organic materials such as methylene blue (MB) by Fenton reaction without any secondary pollution. The catalytic reaction mechanism of transformation of As (III) and degradation of MB was confirmed by fluorescence spectroscopy.

Facile template-free synthesis of 3D flower-like Bi2WO6/MoO3 nanocomposites with ultra-thin sheets and their associated photocatalytic properties under visible light irradiation

Bi2WO6 hierarchical multilayered flower-like assemblies were fabricated by a simple template-free method. This structure composed of a large number of interconnected nanoplates with a mean side length of ca. 20 nm. The unique design was created by nanosheets in all directions which provide high surface area. Numerous nanosheets promote charge carrier transport. Bi2WO6/MoO3 nanocomposites were synthesized by thermal treatment of ammonium heptamolybdate tetrahydrate in Bi2WO6 pores in static air at 400 °C. Prepared photocatalysts were characterized by SEM, TEM, XPS, XRD, BET, PL, IR and DRS. Bi2WO6/MoO3 demonstrated high activity in photodegradation of an azo dye and after 20 min of irradiation, the solution became colorless. Optimization of different parameters such as pH, catalyst dosage, calcination temperature, dye concentration, weight percent of MoO3 to Bi2WO6 was done. Photocatalytic mechanism proposed based on the scavenger usage as well as photoreaction kinetics were studied.

Template‐free synthesis of novel hollow carbon nanospheres with dual active sites as catalyst for fuel cell cathode to improve oxygen reduction reaction performances

A new template-free controlled method is reported herein to prepare the novel hollow carbon nanospheres with dual active sites of FeN4 and FeC3 by in situ growth reaction on graphene nanosheets, labeled as HCN-FNFCG. As-prepared HCN-FNFCG nanomaterials possess hierarchically porous FeN4/FeC3 shells with structures of microporous, mesoporous, and macroporous properties. Moreover, the hierarchically porous HCN-FNFCG nanomaterials with dual active sites of FeN4 and FeC3 have not been reported before. The HCN-FNFCG nanomaterials, as oxygen reduction reaction (ORR) catalysts, are first studied systematically toward cathodic ORR of fuel cell. The measurements have illustrated that HCN-FNFCG-650 has the best ORR performances among these HCN-FNFCG nanomaterials studied. The onset potential of HCN-FNFCG-650 has reached 1.095 V in alkaline electrolyte, and its maximum current density is 6.48 mA cm−2. Additionally, the HCN-FNFCG-650 has also displayed small electrochemical impedance, its Tafel-slope value is 44.25 mV dec−1, much lower than that of the 20% Pt/C (69.57 mV dec−1). And its value of current density is still maintained 92.83% of the initial value after 9000-second continuous tests. High tolerance against methanol crossover is also exhibited for HCN-FNFCG-650. This novel method of template-free synthesis can provide a promising strategy for preparing hollow nanospheres with hierarchically porous shells. And it can be used to design ORR electrocatalysts, electrode materials, or other applications.

Template-free hydrothermal synthesis of hexa ferrite nanoparticles and its adsorption capability for different organic dyes: Comparative adsorption studies, isotherms and kinetic studies

The comparison of adsorption of hazardous dyes such as Evans blue, Congo red and Rhodamine B is studied using novel calcium hexaferrite (CaAl5Fe7O19) nanoparticles, which are synthesized through the solution combustion method. During the synthesis process, the calcium hexaferrite nanoparticles are doped with 15.5% of aluminum nitrate. The synthesized doped-ferrite nanoparticles are characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD). The comparative adsorption studies of three different hazardous environmental chemical pollutants such as Evans blue, Congo red and Rhodamine B dye were investigated by batch adsorption experiments with varying influencing parameters such as dosage effect, dye concentration, pH and contact time. It is found that the maximum adsorption for Evans blue (90.85%) at the wavelength of 608 nm, Congo red (58.17%) at 418 nm, and Rhodamine B (65.6%) is at 627 nm. Freundlich and Langmuir’s adsorption are compared and the results obtained matches well with the Freundlich isotherm model. Such novel materials have the potential for applications in environmental remediation.

Solvothermal and template-free synthesis of N-Functionalized mesoporous polymer for amine impregnation and CO2 adsorption

Abstract In this work, a porous organic polymer (POP) exhibiting abundant N species and rich mesopores was synthesized by solvothermal copolymerization of divinylbenzene (DVB) and 1-vinylimidazole (VI) without the use of any templates. The synthesized POP, abbreviated as P (DVB-VI), was used as the support for pentaethylenehexamine (PEHA) impregnation to prepare solid adsorbents for CO2 capture. The porous and chemical structures of prepared samples were characterized by elemental analysis, N2 adsorption, electron microscopy, infrared spectra, and thermogravimetric analysis. The CO2 capture performance of prepared samples was also systematically investigated by measuring the CO2 adsorption capacities and CO2/N2 selectivities, and the effect of moisture on CO2 adsorption and recyclability of adsorbents was examined. It was found that PEHA-impregnated P (DVB-VI) adsorbents displayed CO2 capacities of as high as 4.56 mmol/g at 75 °C and atmospheric pressure, together with excellent CO2/N2 selectivities and good recycling stability.

Preparation of magnetic mesoporous epoxy resin by initiator-free ring-opening polymerization for extraction of bile acids from human serum

In this work, we reported a simple two-step method for the synthesis of magnetic mesoporous epoxy resin (MMER), including one-pot template-free hydrothermal synthesis of nanoscale amine-functionalized magnetic nanoparticles (MN-NH2) and initiator-free ring-opening polymerization of epoxy resin. The resultant MMER was characterized in detail by transmission electron microscope (TEM), Fourier transform-infrared (FT-IR) spectra, X-ray photoelectron spectroscopy (XPS), thermogravimetic analysis (TGA) and magnetization curves. These results demonstrated successful synthesis of MMER with sufficient magnetic property and excellent thermal stability. The epoxy resin was covalent bonding MN-NH2 on and synthesized by hydrophobic monomers, so the MMER exhibited excellent adsorption quantity for hydrophobic bile acids. The MMER was used as magnetic solid-phase extraction (MSPE) sorbent, and combined with liquid chromatography-tandem mass spectrometry to extract and monitor 11 kinds of bile acids from serum sample. The proposed MSPE combined with LC–MS/MS method exhibited low limit of detection between 0.1 and 5 ng mL−1. In blank serum sample, 9 kinds of bile acids were detected, and ranged from −2.29 ng mL−1 to 6.86 ng mL−1. In standard addition recovery test, the recovery values of detectable bile acids ranged 102.4% to 108.5%, 96.0% to 104.0% and 82.3% to 103.3% when spiked with 0.2, 2.0 and 20 ng mL−1, respectively. The intra- and inter-day precision (n = 6) ranged 3.7% to 5.9% and 7.0% to 9.5%, respectively. The above results demonstrated that the MSPE combined with LC–MS/MS method was accurate and effective for quantitative determination of bile acids from complex biological samples.

Facile template-free synthesis of Ni-SiO2 catalyst with excellent sintering- and coking-resistance for dry reforming of methane

Ni-SiO2 catalysts were synthesized by facile template-free hydrothermal method with ammonia-assisted via using low-cost silica sol as precursor and successfully employed to dry reforming of methane reaction. It was found that ultra-small Ni nanoparticles around 3.2 nm rationally obtained with high dispersion. The strong metal-support interaction generated from the in-situ ammonia-assisted process further stabilized the Ni species during the DRM reaction. Furthermore, the high activity, stability and H2/CO ratio of Ni-SiO2 remained initial value even continued reacting at 700 °C for 30 h. Almost no visualization of metal growth and carbon deposition were observed on the spent catalyst.

Adsorptive Removal of Dyes from Aqueous Solution by KMnO4-Modified Rice Husk and Rice Straw

Rice husk (RH) and rice stalk (RS), the abundant biomasses, have been tentatively explored as the renewable biochar which were prepared by means of hydrothermal and activation processes, and the synthetic procedure is quite simple and easy to be scaled up for industrial applications. In this work, the removal of malachite green (MG) was investigated by KMnO4-treated RH and RS as the efficient adsorbents at various experimental conditions. Various operational parameters such as initial dye concentration, adsorbent dosage, and solution temperature in batch systems were investigated on the use of RH and RS. The adsorption isotherm model (Langmuir and Freundlich isotherms), kinetic model (pseudo-first-order, pseudo-second-order, and Elovich models), and the adsorption mechanism (intraparticle diffusion and Boyd models) were studied. It showed that that the Langmuir model and Elovich model are suitable for describing the adsorption process, and the diffusion rate of surface adsorption and the particle diffusion rate jointly affect the reaction rate of adsorption. This facile, efficient, and template-free synthesis strategy holds great promise for preparing novel porous biochar from renewable biomass resources for application in adsorbents.

Template-free synthesis of porous Mo3P/MoP nanobelts as efficient catalysts for hydrogen generation

Hydrogen has attracted extensive attention as a potential alternative energy and many achievements have been made in the research of transition metal phosphide catalysts, but further improvements are still strongly demanded. In this report, we propose a novel strategy for the template-free synthesis of Mo3P/MoP porous nanobelts as efficient catalysts for hydrogen generation. The porous structures can give more active sites, and the presence of Mo3P can further improve the internal electron transfer ability through the strong bond. Thus, the porous Mo3P/MoP hybrid catalyst exhibits an outstanding hydrogen evolution activity and a good stability. This study may provide a facile and effective strategy for the improvement of transition metal phosphide catalysts by controlling the structures and compositions.

Template-Free Synthesis and Properties of Mesoporous Calcium Titanate

X-ray amorphous powder was obtained via template-free synthesis, including the sol–gel process and coprecipitation. We showed that mesoporous calcium titanate is formed during the calcination of a powder up to 800°C. The structure and morphology of the samples thermally processed at 200, 400, 600, and 800°C are studied with scanning electron microscopy, X-ray phase analysis, thermogravimetric analysis, and IR spectroscopy. Low-temperature adsorption–desorption of nitrogen vapors and laser diffraction analysis showed that calcium titanate powder has a highly developed surface of over 100 m2/g with average particle size from 99 to 290 nm and significant pore volume.