Assisted Co-precipitation Method Research Articles

Rice-Like ZnO Architecture: An Eminent Electrode Material for High-Performance Ultracapacitor Application

In this investigation, the rice-like ZnO material was successfully synthesized using the CTAB assisted chemical co-precipitation method followed by a probable annealing process. The internal structure, thermal properties, phase studies, and morphological features were analyzed using Fourier transform infrared spectroscopy (FTIR), Thermogravimetric analysis (TGA), X-ray diffraction analysis (XRD), and scanning electron microscopy (SEM) techniques, respectively. The CTAB serves as a template that influences the fabrication process and exclusively alters ZnO materials’ morphological features. The high concentration of the CTAB (2 mM) template provides a rice-like ZnO structure. The synthesized ZnO material’s electrochemical properties were inspected using cyclic voltammetry (CV) and galvanostatic charge/discharge studies (GCD). The CV curves provide a specific capacitance of 457 F g−1 at a scan rate of 5 mVs−1, whereas the GCD curves affirm a specific capacitance of 449 F g−1 at a current density of 1 Ag−1. Furthermore, it also exhibits high cyclic stability with 94% of the initial capacitance retained even after continuous 2000 CV cycles at a scan rate of 100 mV s−1. These results signify that the rice-like ZnO material could be a significant postulant for ultra-capacitor electrode applications.

Tuning (003) interplanar space by boric acid co-sintering to enhance Li+ storage and transfer in Li(Ni0.8Co0.1Mn0.1)O2 cathode

High nickel layered oxides (LiNi0.8Co0.1Mn0.1O2, NMC811) demonstrate high capacity (≥ 200 mA h/g) and low cost, making them increasingly attractive as a high energy active cathode to replace LiCoO2 or LiFePO4 for lithium ion batteries. Nevertheless, their large scale practical applications are still inhibited by the low structural stability, insufficient rate capability and cyclability. In this work, a stable and safe LiNi0.8Co0.1Mn0.1O2 cathode was synthesized by facile oxalic acid assisted co-precipitation method. Boric acid has been chosen and utilized as a co-sintering agent to enhance the electrochemical performance via fine tuning internal interplanar space between transition metal oxide (003) layers. The B03 sample with 3.0 at% of boron doping exhibited a sustainable reversible capacity as high as 220 mA h g−1 with approximate 97% capacity retention after 100 cycles at 0.5 C charging/discharging rate. It also delivered 93 mA h/g under 10 C rate testing. In the long-term cycling test, this B03-NMC 811 cathode demonstrated 83% capacity retention after 300 cycles at 5 C cycling test. Appropriate adding of boron not only enhanced their C-rate capability and cyclability but also improved their structural stability during repetitive charging and discharging process through ex situ XRD measurement. The c axis variation of B03-NMC 811 cathode between 3.7 V and 4.3 V was reduced by 7.6% (0.014 Å) as compared to the pristine one. However, larger quantity (5.0 at%) of boron degrades the electrochemical performance induced by increased Li/Ni disorder. Thereafter, this enhancement in both electrochemical performance and structural stability benefits from the optimized interplanar space between transition metal oxide (003) layers, which can be tuned precisely by such a simple but novel co-sintering process with boric acid. This approach opens the door to structural modification and optimization of NMC811 cathode to satisfy the demanding performance and safety requirements of electric vehicles.

Local iron ore identification: comparison to synthesized Fe3O4 nanoparticles obtained by ultrasonic assisted reverse co-precipitation method for Auramine O dye adsorption

Local iron ore identification: comparison to synthesized Fe3O4 nanoparticles obtained by ultrasonic assisted reverse co-precipitation method for Auramine O dye adsorption

The rare earth dopant (La, Gd, Sm & Y) modulated grain boundary energy barrier suppression in BaZrO3-BaCeO3 solid solution

The charge depletion near the grain boundary region in proton-conducting BaZrO3 electrolyte results in large potential barrier for the proton migration. Alternatively, a barium zirconate-cerate solid solution has been shown to improve the protonic conductivity by lowering the charge depletion along the grain boundary. Here, we report the modulation in grain boundary resistance of barium cerate – zirconate solid solution in the presence of trivalent rare-earth dopants differing in ionic radii. A hydrothermal assisted co-precipitation method was used for the preparation of two solid solutions, BaCe0.5−xZr0.5MxO3 and BaCe0.5Zr0.5−xMxO3 (M = La, Gd, Sm, Y; x = 0.10). The investigation of electrical properties revealed that the conductivity has a strong correlation with the ionic radii of the dopant and its interaction with the mobile protons. In comparison to larger sized dopants, the dopants with smaller ionic radii such as Y3+ has the lower trapping sites for proton, thereby, achieving the higher conductivity of 61.2 mS cm-1 at 600 °C under reducing atmosphere. The space charge quantification through Mott-Schottky approximation showed a negligible variation in barrier potential. However, the inclusion of Ce reduced the defect segregation towards the grain boundary due to the electrostatic interaction which in turn reduced the formation of the space charge layer thereby improving the conductivity.

BaTiO3@rGO nanocomposite: enhanced photocatalytic activity as well as improved electrode performance

Herein, we reported the preparation of BaTiO3 nanoparticles and BaTiO3@rGO nanocomposite by sol-gel route and microwave assisted co-precipitation method respectively. A series of analysis such as X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, UV-visible absorption, photocatalytic activity, photoluminescence and Brunauer-Emmett-Teller (BET) method were employed to determine the properties of prepared samples. The dielectric properties of BaTiO3 nanoparticles and BaTiO3@rGO nanocomposite were studied at different frequencies and different temperatures. Photocatalytic performance of obtained BaTiO3@rGO nanocomposite was evaluated via photocatalytic degradation process of methylene blue (MB) as a model dye under irradiation of visible light. The cumulative outcome of results indicated the superior performance of BaTiO3@rGO nanocomposite as photocatalyst when compared with pure BaTiO3 nanoparticles, which might be attributed to distensible surface area and effective separation of photo-excited electron-hole pairs. Our findings demonstrate that the prepared nanocomposite as reported here may be utilized as photocatalyst for degrading organic pollutants and as electrode in charge storage devices.

Effects of surfactant-assisted synthesis Fe3(PO4)2∙8H2O and its purity and morphology on the performance of LiFePO4/C cathode materials

The synthesis of high purity and crystallinity Fe3(PO4)2·8H2O precursor by polyvinyl pyrrolidone (PVP)–assisted co-precipitation method is reported, and the morphology-controlled tiny and uniform primary particles material has also been obtained. Moreover, the fore-mentioned Fe3(PO4)2∙8H2O was used to synthesize LiFePO4/C via carbothermal reduction. All the materials were systematically characterized by various analytical, spectroscopic, and imaging techniques. Fe3(PO4)2∙8H2O exhibits stronger affinities within primary particles and homogeneity, attributed to PVP, which can greatly improve the properties of LiFePO4/C. The resulting high purity Fe3(PO4)2∙8H2O gave highly crystalline of LiFePO4/C. In addition, LiFePO4/C prepared with PVP demonstrated excellent electrochemical performance of initial discharge capacities at 0.2 C, 0.5 C, 1 C, 2 C, and 5 C are 163.4, 160.9, 155.1, 146.2, and 126.5 mAh g−1, respectively.

Understanding the high performance of an iron-antimony binary metal oxide catalyst in selective catalytic reduction of nitric oxide with ammonia and its tolerance of water/sulfur dioxide

In recent years, Fe-based catalysts for the selective catalytic reduction of NO with NH3 (NH3-SCR) have been attracting more attention. In this work, a novel Fe-Sb binary metal oxide catalyst was synthesized using the ethylene glycol assisted co-precipitation method and was characterized using a series of techniques. It was found that the catalyst with a molar ratio of 7:3 (Fe:Sb) displayed the best NH3-SCR activity with 100% conversion of NOx (nitrogen oxides) over a wide temperature window and with good resistance to H2O + SO2 at 250 °C. The X-ray photoelectron spectroscopy (XPS) and in situ diffused reflectance infrared Fourier transform spectroscopy (in situ DRIFTS) of NOx adsorption results suggested that strong electron interactions between Fe and Sb in Fe-O-Sb species existed and electrons of Sb could be transferred to Fe through the 2Fe3+ + Sb3+ ↔ 2Fe2+ + Sb5+ redox cycle. The introduction of Sb significantly improved the adsorption behaviour of NOx species on the Fe0.7Sb0.3Ox surface, which benefitted the adsorption/transformation of NOx, thereby facilitating the NH3-SCR reaction. In addition, the Fe0.7Sb0.3Ox catalyst demonstrated a good tolerance of H2O and SO2, since the decomposition of NH4HSO4 on the catalyst surface was promoted by the introduction of Sb.

Engineering the Hierarchical Heterostructures of Zn–Ni–Co Nanoneedles Arrays@Co–Ni-LDH Nanosheets Core–Sheath Electrodes for a Hybrid Asymmetric Supercapacitor with High Energy Density and Excellent Cyclic Stability

To meet the requirement for the high-ranked positive electrode materials having auspicious pseudocapacitive features for potential application in energy storage devices, the suitable designs of unique core–shell heterostructures featuring mixed transition metal oxide and layered double hydroxide (LDH) are highly needed and have been progressing expeditiously in recent years. Herein, 3D hierarchical zinc–nickel–cobalt (ZNCO)@Co–Ni-LDH (LDH-1 and LDH-2) core–shell nanostructured arrays on Ni foam as a pseudocapacitive electrode are prepared by using a facile hydrothermal and metal–organic framework (MOF) assisted coprecipitation method. FE-SEM images show that the core 1D ZNCO and shell 2D Co–Ni-LDH are well interconnected to form 3D porous and hierarchical ZNCO@Co–Ni-LDH core–shell nanostructures, leading to the fast and efficient transmission/transfer of both electrolyte ions and electrons, due to the higher electroactive surface areas and enhanced electrical conductivity. In a three-electrode system, the ZNCO@Co–Ni-LDH-2 electrode material delivers excellent electrochemical performance with higher specific capacitance of 2866 F g–1 at 1 A g–1 with ultrahigh capacitance retention of 68.35% at a higher current density of 10 A g–1 and excellent life span of 89% capacitance retention after 8000 cycles. Moreover, the sandwiched asymmetric supercapacitor (ASC) device using ZNCO@Co–Ni-LDH-2 as the positive electrode and N-doped graphene hydrogel (NGH) as the negative electrode exhibits superior specific capacitance (178 F g–1 at 1 A g–1), outstanding rate capability (70.22% at 10 A g–1), excellent life span (91.2% after 8000 cycles at 10 A g–1), and very high energy density (63.28 W h kg–1 at power density of 796.53 W kg–1).

Dielectric barrier discharge plasma combined with nano catalyst for aqueous amoxicillin removal: Performance modeling, kinetics and optimization study, energy yield, degradation pathway, and toxicity

Dielectric barrier discharge (DBD) plasma has been increasingly used for degrading the emerging environmental pollutants. The UV–Vis irradiation and high energetic species produced by DBD plasma are two promising factors to couple DBD with catalysts in order to improve the degradation rate and reduce the production of harmful intermediates. Nowadays, searching to identify a powerful catalyst-plasma system for removing persistent pollutants is still an urgent need. Therefore, in the current study, a useful ZnO/α-Fe2O3 composite catalyst was synthesized using a low-temperature assisted co-precipitation method and was applied in combination with the DBD reactor for the degradation of amoxicillin (AMX), the antibiotic, in water. The morphology and structure of ZnO/α-Fe2O3 samples were characterized before and after the plasma DBD. In addition, the interaction effects among contact time, AMX initial concentration, composite catalyst loading, and solution pH on AMX degradation were assessed by the response surface method (RSM). Moreover, the performance evaluation, optimization, kinetics model, energy yield, degradation pathway, and toxicity of the plasma-catalysis process were studied. As a major result, the AMX degradation rate reached 99.3% during 18 min at the peak voltage of 15 kV, and ZnO/α-Fe2O3 load of 0.4 g L−1, AMX initial concentration of 16 mg L−1, and pH of 4.5 with a rate constant of 0.198 min−1, energy yield of 3 g kW−1 h−1, without any effluent toxicity. Finally, it can be concluded that the DBD- ZnO/α-Fe2O3 system exhibits a great and eco-friendly potential for aqueous AMX degradation.

Interplay of structural, optical, and magnetic properties of Ce1-xNdxO2-δ nanoparticles with electronic structure probed using X-ray absorption spectroscopy

The CeO2-δ and Ce1-xNdxO2-δ (x = 0.02, 0.04 and 0.06) nanoparticles, synthesized by microwave assisted co-precipitation method have been investigated for structural, optical, electronic structure and magnetic properties using X-ray diffraction, transmission electron microscopy, Absorption spectroscopy, surface enhanced Raman spectroscopy, X-ray absorption spectroscopy (XAS), and SQUID magnetometer. TEM and XRD measurements indicate face-centred cubic fluorite structure of CeO2 with Fm-3m space group. The Raman spectroscopy indicates that all the Nd3+-doped CeO2 samples downward shifting of F2g band with introduction of oxygen vacancies. Further, band gap decrement has been observed with incorporation of Nd3+ ions in CeO2 lattice. The XAS spectra of Ce M − edge clearly indicate changed valence state of Ce ions from Ce4+ to Ce3+ with Nd3+ doping concentrations. The formation of oxygen vacancies is also confirmed with O K- and Nd M-edges XAS analysis. It is revealed that new complexes Ce3+-VO- Nd3+ and Ce4+- VO –Ce3+ have been introduced to support FM ordering through the development of F+-centres. Therefore, it can be concluded that oxygen vacancies play a prominent role in improving the ferromagnetic and various properties of these nanomaterials, to make them suitable for many applications as UV blocker, Photocatalyst, Spintronics and Optoelectronics applications.

Essential oil impregnated luminescent hydroxyapatite: Antibacterial and cytotoxicity studies.

In this study, porous fluorescent nanocrystalline erbium doped hydroxyapatite (eHAp) was synthesized via hydrothermal assisted co-precipitation method. Eucalyptus oil (EU), frankincense oil (FO), Tea tree oil (TTO), wintergreen oil (WO) were successfully absorbed into eHAp pellet by vacuum filtration technique using Buckner funnel. Phase crystallization, fluorescence property and microstructure of eHAp were confirmed by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Photoluminiscence spectroscopy (PL) and Field emission scanning electron microscopy (FESEM). Strong antimicrobial activity was observed for EU, TTO and WO on both E. coli and S. aureus mediated by cell membrane damage and leakage of cytoplasmic components. The oil absorbed eHAp nanocomposites were found to be moderately biocompatible with normal WI-38 cells up to MIC concentration various time scale. The nanocomposites showed significant cytotoxic activity on breast cancer cell line MDA-MB 468 and the fluorescent property of the eHAp was utilized to visualize internalization of particles in the cells. The release profile of the oils from the eHAp matrix showed pH dependent release indicated that the porous matrix can be used as a suitable carrier for modulated and sustained release of bioactive components. Thus, given the multifunctional attributes these natural essential oil-based nanocomposites show great promise as an alternative to conventional therapeutic treatments.

Highly monodisperse and colloidal stable of L-serine capped magnetite nanoparticles synthesized via sonochemistry assisted co-precipitation method

Highly monodispersed magnetite nanoparticles (MNPs) were successfully prepared by means of a sonochemistry-assisted co-precipitation method in the presence of L-serine (L-ser). In order to understand the effect of the L-serine on the development of nanoparticles, various concentrations (0, 1, 3 and 5 mmol) of L-ser were employed. In this study, a conventional co-precipitation method was also performed to prepare MNPs (denoted as MNP-1) as a comparison. The MNPs prepared via sonochemistry-assisted co-precipitation method (MNP-2) have better crystallinity and morphological uniformity than MNP-1, which were observed by XRD and TEM measurements, respectively. Synergistically, the introduction of L-ser as a capping agent during the ultrasound irradiation significantly improved the particle size monodispersity and colloidal stability of MNP-2. In addition, the magnetic sensitivity of MNP-2 (Ms = 57.12 emu g−1) was not altered significantly even with the addition of 5 mmol of L-ser (Ms = 48.34 emu g−1). This investigation shows that the L-ser acts not only as a capping agent to improve the colloidal stability of nanoparticles but also as a particle size controlling agent.

Influence of Nickel concentration on the photocatalytic dye degradation (methylene blue and reactive red 120) and antibacterial activity of ZnO nanoparticles

This study assessed the synergistic effect of Ni concentration and ultrasonic assisted process on the photocatalytic dye degradation efficiency towards methylene blue (MB) and reactive red 120 (RR120) and antibacterial activity against various bacteria of ZnO nanoparticles. XRD confirms the absence of any other impurity peaks in Nickel (Ni) doped ZnO nanoparticles, disclose that Ni doping influences the lattice structure of Zn. The obvious red-shift with the increase of Ni concentration results in decreased band gap and transmittance. SEM micrograph confirms the formation of hexagonal rod and sheet like nanostructures in the Ni doped ZnO nanoparticles by the ultrasonic assisted co-precipitation method. The Ni doped ZnO nanoparticles control the recombination of charge carriers and increase the photocatalytic degradation of MB and RR120. The antibacterial result revealed that 5% Ni substituted sample is effective as an antibacterial agent to prevent the bacterial contamination. 5% Ni doped ZnO nanoparticles synthesized by ultrasonic assisted coprecipitation method is an excellent candidate for removal of methylene blue and bacteria.

Structure and magnetic properties of ultrafine superparamagnetic Sn-doped magnetite nanoparticles synthesized by glycol assisted co-precipitation method

The usage of ethylene glycol as high boiling solvent results in the formation of ultrafine, highly crystalline tin doped magnetite nanoparticles with an average size equal to 4.85 nm. The oxidation of Sn2+ ions to Sn4+ ions under the formation of magnetite structure was observed. This process was related to the reduction of Fe3+ ions to the Fe2+ ions. Thereafter, Sn4+ ions can replace Fe3+ ions in the magnetite structure, which affects the magnetic properties. The synthesized Fe3O4:Sn4+ nanoparticles have superparamagnetic behavior, high saturation magnetization equal to 49.7 emu/g and very low coercivity equal to 13.29 Oe. The content of Sn4+ ions in synthesized nanoparticles was equal to 1.87 at.%

Dehydration-Dehydrogenation of Ethanol on Chromia-Alumina and Magnetite-Alumina Nano-Composite Catalysts

Chromia-alumina and hematite-alumina nano-composite materials are prepared by ultrasonic assisted co-precipitation method. The prepared materials are tested for their suitability in the catalytic conversion of ethanol in a fixed bed reactor at a space velocity 0.6 h–1 by using either O2 and/or N2 as carrier gas with a flow rate of 40 mL/min at temperature range 200–500°C. The prepared nano-composite materials are characterized by XRD, DTA, TGA, DLS, TEM, NH4-TPD and surface measurements, which informed the formation of amorphous chromia-alumina material with low surface area, wide pore size and weak surface acidity. On contrary crystalline hematite-alumina with high surface area, narrow pore size and large number of strong surface acidity is formed. The catalytic activity results indicate that the main converted products are acetaldehyde, ethylene and diethyl ether. The dehydrated products (ethylene and diethyl ether) are prevailing by using chromia-alumina nano-composite in the presence of nitrogen carrier gas with ethanol conversion 74% at 500°C. In the presence of oxygen carrier gas, acetaldehyde is the predominant product with selectivity 38.5%. Hematite-alumina nano-composite emphasizes the same trend towards the formation of the dehydrogenated compounds, at 500°C in the presence of the oxygen carrier gas (acetaldehyde) with selectivity 42%, besides formation of the dehydrated products with selectivity 32.8%.

Physical, Structural and Dielectric Parameters Evaluation of New Mg1-x Cox NiyFe2-yO4 nano-ferrites Synthesized via Wet Chemical Approach

Department of Chemistry, Institute of Natural Sciences, University of Gujrat, Gujrat 50700, Pakistan The surfactant assisted co-precipitation method has been used to synthesize the Co2+ and Ni2+ substituted magnesium nanoferrites. The Co2+ and Ni2+ ions substitute the Mg2+ and Fe3+ ions from the magnesium ferrites, respectively. To study the effect of substituted ion concentrations on the dielectric performance of the MgFe2O4 spinel ferrites. The substituted magnesium nanoferrites with the compositions Mg1-x Cox NiyFe2-yO4 (x, y = 0.0, 0.1, 0.2, 0.3, 0.4, and 0.5) were synthesized to notice the effect of substituted ions concentration on the dielectric properties. Thermogravimetric analysis of the precursor precipitates was taken to investigate the stable spinel phase formation temperature. The X-ray diffraction analysis of the all substituted samples confirms the successful formation of the stable spinel phase and also exposes the effects of substituted ions on the crystal structure and unit cell constants. The presence of a characteristic absorption band (400 cm−1, 550 cm−1) of spinel ferrites in the Fourier Transform Infra Red (FT-IR) spectrum of substituted magnesium nanoferrites also confirms the formation of desire phase. The effect of temperature on the conductivity of the all substituted samples was observed within the temperature range of 25°C–300°C by two-probe direct current electrical resistivity measurements. Dielectric measurements of the substituted magnesium nanoferrites were carried out to study their magnetic behavior. The inverse relation of the dielectric parameters of the all substituted magnesium nanoferrites with frequency shows their excellent potential for devices that operate at higher frequencies.Department of Chemistry, University of Okara, Renala Khurd, Okara, Pakistan Department of Chemistry, Allama Iqbal Open University, H-8, Islamabad 45320, Pakistan.

High-yield synthesis of Ce modified Fe-Mn composite oxides benefitting from catalytic destruction of chlorobenzene.

Ce–Fe–Mn catalysts were prepared by an oxalic acid assisted co-precipitation method. The influence of Ce doping and calcination temperature on the catalytic oxidation of chlorobenzene (as a model VOC molecule) was investigated in a fixed bed reactor. The Mn3O4 phase was formed in Ce–Fe–Mn catalysts at low calcination temperatures (<400 °C), which introduced more chemisorbed oxygen, and enhanced the mobility of O atoms, resulting in an improvement of the reduction active of Mn3O4 and Fe2O3. Additionally, CeO2 has strong redox properties, and Ce4+ would oxidize Mnx+ and Fex+. Therefore, the interaction of Ce, Fe and Mn can improve the content of surface chemisorbed oxygen. As compared with Fe–Mn catalysts, the catalytic conversion of chlorobenzene over Ce(5%)–Fe–Mn-400 was about 99% at 250 °C, owing to high specific surface area, Mn3O4 phase, and Ce doping. However, with the increase in roasting temperature, the performance of the catalysts for the catalytic combustion of chlorobenzene was decreased, which probably accounts for the formation of the Mn2O3 phase in Ce–Fe–Mn-500 catalysts, leading to a decrease in the specific surface area and concentration of chemically adsorbed oxygen. As a result, it can be expected that the Ce–Fe–Mn catalysts are effective and promising catalysts for chlorobenzene destruction.

Synthesis of Carbon Stabilized Zinc Oxide Nanoparticles and Evaluation of Its Photocatalytic, Antibacterial and Anti-biofilm Activities

The present study reports a microwave assisted chemical co-precipitation method to synthesize carbon stabilized zinc oxide nanoparticles (ZnO NPs). The NPs were characterized by using UV–visible spectrophotometer, scanning electron microscopy (SEM) and Energy-dispersive X-ray spectroscopy (EDS). UV–visible absorption spectra showed an absorption maximum at 385 nm. Hydrodynamic size distributions of ZnO NPs were measured by using particle size analyzer. ZnO-C-0.5 showed the lowest size, 55 nm compared to other particles. All the carbon coated particles showed a zeta potential of > − 30 mV indicates the stability of the particles. The rate of ·OH formation was higher in case of ZnO-C-0.5 compared to ZnO-C-0.25, ZnO-C-0.75 and ZnO-C-1. ZnO-C-0.5 showed excellent dye degradation efficiency under visible light and followed by ZnO-C-0.75, ZnO-C-0.25 and ZnO-C-1 with a degradation efficiency of 63.45, 58.49, 47.97 and 47.31% respectively. In addition to this ZnO-C-0.5 exhibited enhanced photostability and reusability. The antibacterial and antibiofilm activity of ZnO-C NPs were studied by using Staphylococcus aureus and Pseudomonas aeruginosa bacterial species. At 10 µg/L, ZnO-C-0.5 showed 100% inhibition of both the bacterial species. The increase or decrease in carbon ratio decreased the photocatalytic efficiency and antibacterial and antibiofilm effect. The presence of carbon enhanced the antibacterial and antibiofilm effects and ZnO-C-0.50 exhibited highest activity.

Hydrogen production from ethanol steam reforming over Co–Ce/sepiolite catalysts prepared by a surfactant assisted coprecipitation method

A series of Co–Ce/Sepiolite (SEP) catalysts were prepared by surfactant-assisted coprecipitation route and subsequently evaluated for hydrogen production from ethanol steam reforming. The effects of the types and quantities of surfactants such as Cetyltrimethyl Ammonium Bromide (CTAB) and Polyvinyl Pyrrolidone (PVP) on catalysts microstructures were investigated by means of N2 adsorption-desorption, XRD, H2-TPR, Raman, XPS, SEM, and TEM. The results demonstrated that the function of surfactants complexation with Co/Ce precursors enlarged the metal interparticle distance, led to the surface enrichment of Co/Ce atoms and provoked diverse Co–Ce interfaces, which could both enhance the reforming behavior and restrain the amorphous coke during reaction. Meanwhile, the optimal complexation effect of CTAB on Co–Ce/SEP-C0.4 (CTAB:Mδ+ = 0.4) gave it superior reducibility, surface content of Co/Ce atoms and relative abundance of oxygen vacancies. Consequently, Co–Ce/SEP-C0.4 presented the best ethanol conversion (96.2%), hydrogen yield (77.9%) and the uppermost catalytic stability (100 h) during ESR reaction. In addition, the scatter modes of surface Co/Ce particles and forms of Co–Ce interfaces significantly depended on surfactant types.

Dilatometer studies of praseodymium doped ceria: Effect of synthesis methods on sintering behaviour

Praseodymium-doped ceria (Ce0.9Pr0.1O2, PDC), as an electrolyte material for IT-SOFCs, is investigated with respect to the effect of synthesis method and a detailed analysis was carried out to understand the effect on crystallite size, morphology, specific surface area and sintering behaviour. The various synthesis routes such as microwave assisted co-precipitation method, room temperature co-precipitation method and EDTA-citrate complexing method was adopted for the synthesis of praseodymium doped ceria-based nano-materials. XRD pattern confirms the fluorite-type crystal structure of ceria and Raman spectroscopy analysis confirms the structure with the presence of oxygen vacancies. PDC synthesised by microwave assisted co-precipitation method using isopropyl alcohol as solvent exhibited better sintering activity, reduced the sintering temperature and promoted the densification rate when compared to other synthesis methods with uni-model shrinkage behaviour with shrinkage maxima at 765 °C. Based on two sintering models (CHR/Dorn method), the initial stage sintering mechanism was investigated in the present study and confirmed that the grain boundary diffusion (m = 2) as the dominant mechanism and the activation energy was found to be 116 kJ/mol (CHR model) and 176 kJ/mol (Dorn Method) for initial stages of sintering for PDC material synthesised by microwave assisted co-precipitation method using isopropyl alcohol as solvent.