Average Crystal Size Research Articles

Catalytic conversion of n-Dodecane to lower olefins hydrogen carriers over bran-shaped modified MCM-22 zeolite catalyst: SiO2/Al2O3 ratio effects

The demand-supply gap for light olefins and aromatics has been enormous in recent years. This imbalance is anticipated to grow exponentially due to their extensive use in manufacturing plastics, textiles, pharmacological intermediates, climate-neutral synthetic fuels, and hydrogen carriers. Production of light olefins through the catalytic cracking of naphtha is widely regarded as one of the most prestigious methods. Despite this, selecting an effective and efficient catalyst is one of the most challenging aspects of the scaling-up process. In this study, a highly active, modified MCM-22 catalyst has been synthesized by a hydrothermal method. Various techniques are used for the characterization of catalysts, including scanning electron microscopy (SEM), X-ray diffraction (XRD), N2 adsorption-desorption, temperature-programmed desorption of ammonia (NH3-TPD), and solid-state nuclear magnetic resonance experiments (NMR) with Al and Si. The cracking of n-dodecane to lower olefins was performed, and it was found that the conversion rates were highly correlated with the SiO2/Al2O3 ratio of the MCM-22 samples. Sample Si0.5 (SiO2/Al2O3 ∼ 28.9) showed a typical photograph of the MWW phase with a bran or flake shape in a stacking mode. The Si0.5 sample has a superior external surface area than other samples (up to ca. 130 m2/g) caused by a smaller particle with an average crystal size of around 15 nm, resulting in maximum catalytic performance towards light olefins. It was discovered that Si0.5 had a diminishing tendency in the paraffinic selectivity but had a robust selectivity for olefins (propylene and butylene in particular). This research may provide academics and the industry with new prospects for improving the catalytic cracking of n-dodecane into light olefins.

Preparation and Characterization of TiO2 Nanoparticles With and Without Magnetic Field Effect Via Hydrothermal Technique

With and without the use of magnetic fields, titanium dioxide (TiO2) nanoparticles were synthesized using the hydrothermal method at extremely high temperatures and pressures. Titanium tetra isopropoxide [Ti(C12H28O4)] was used for the preparation, which was performed at pH 7 and under temperatures of 160 and 190 ˚C. UV spectroscopy, XRD crystallography, FE-SEM microscopy were used for characterizations. From UV spectroscopy, the energy gap values were clearly affected by the increase in temperature and the presence of the magnetic field. At the temperatures of 160 and 190 oC for TiO2 without magnetic field, FE-SEM microscopy images have shown an average crystal diameter of 13.436 and 12.551 nm, respectively. While for TiO2 with the presence of magnetic field, the crystal diameters were found to be 14.665 and 14.468 nanometers, respectively, at same temperatures. Additionally, XRD analysis has revealed that the average crystal size of TiO2 at 160 and 190 ˚C without a magnetic field is 13.13 and 11.59 nanometers, respectively. While the crystal sizes for TiO2 in the presence of a magnetic field were determined to be 13.19 and 12.93 nanometers, respectively.

Investigate the effect of hydrothermal temperature on the structure and characterization of 20 % ZnO-Cu2O nanocomposite

The ZnO with 20 mol.% was hybridized with Cu2O to fabricate nanocomposites (20 % ZnO-Cu2O (ZC NCs)) were prepared by hydrothermal method at the investigated temperatures of (120, 200 and 250) ℃. The structural properties and characterization of the materials were investigated by physical measurements including: XRD, SEM, EDX and solid sample UV-Vis spectra. The results showed that the fabricated material samples consist of two crystalline phases (ZnO wurtzite and Cu2O octahedra) with calculated lattice parameters that were suitable for each type of crystal of the material. The average crystal sizes of the ZC120, ZC200 and ZC250 samples were (20.08, 20.36 and 22.50) nm respectively, which were grown lager when the hydrothermal temperature increase. The optical bandgap energy (Eg) of the ZC120, ZC200 and ZC250 material samples was determined to be (2.51, 2.52 and 2.56) eV, respectively. These Eg values of the fabricated ZC NCs samples were intermediate between the two types of ZnO (Eg ~ 3.37 eV) and Cu2O (Eg ~ 2.17 eV) materials, and was valid in the excitation region of visible light.
 ® 2023 Journal of Science and Technology − NTTU

Effects of nucleating agent content on the microstructure and macroscopic performances of polypropylene analyzed by non‐isothermal crystallization behaviors and isothermal crystallization morphologies

AbstractDirect attainment of the crystal state corresponding to desired performances in processing can improve the productivity of semi‐crystalline polymer products. This work tried to propose the idea to approach the target by exploring the effects of nucleating agent content on non‐isothermal crystallization kinetics, isothermally crystallization morphologies and macroscopic properties of polypropylene (PP). The nucleating agent content varied from 0 to 0.5 phr, and all samples were prepared by melting blending at 180°C as the antioxidant and lubricant ensured fine stability and processing. The differential scanning calorimetry results and non‐isothermal crystallization kinetics indicated that introducing 0.3 phr nucleating agent advanced both initial crystallization and melting about 10°C and improved crystallization rate and crystallinity. Besides, 145°C was determined as an isothermal crystallization condition by setting temperature gradient, and the crystallization kinetics were described by a power‐law equation well. The average crystal size was refined to 40 μm uniformly and crystallization time was reduced to 1.5 min as loading 0.5 phr nucleating agent, contributing to the significant improvements in tensile and physical properties. Thus, adding such a short‐time heat insulation procedure into the non‐isothermal cooling stage during processing can obtain desired crystal state directly with loading adequate nucleating agent.

Crystal Structure Analysis of Graphene Oxide based on Bamboo “Betung” Synthesized By Modi-Fied Hummer Method

Bamboo is a non-timber forest product with a very large population in Indonesia. One of them is bamboo betung which can be found from the lowlands to the highlands but has not been used properly. Therefore, research was conducted to utilize bamboo betung to benefit the society. In this study, the synthesis of graphene oxide (GO) from bamboo betung stems will be carried out. The purpose of GO synthesis to further observe the crystal structure and crystal size of GO itself because it can be applied in various fields such as wave absorbers, radio frequency electronics, data display panels, and photovoltaic cells. GO synthesis was carried out using the Modified Hummers Method. The sintering temperatures used in this study were 300oC, 350oC, 400oC and 4500C. GO characterization was carried out using XRD and FTIR to reveal the system of crystal, crystal structure, and size, in addition functional groups, and phases of graphene oxide. GO has an average crystal size of 23.30165 nm as the largest average crystal size. GO layer is formed due to the bond between Carbon (C), Hydrogen (H) and Oxygen (O). GO Layer can be typed at any temperature variations carried out..

Hydrogen catalytic performance of hybrid Fe3O4/FeS2/g-C3N4 nanocomposite structures

In this work, Fe3O4/FeS2/g-C3N4 nanocomposites were developed for catalytic hydrogen generation from sodium borohydride. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and environmental scanning electron microscopy (ESEM) were used to analyze these nanocomposites. The XRD diffraction peaks of Fe3O4 and FeS2 cubic phase showed an average crystal size of calculation of 15 and 20 nm. ESEM micrographs showed a 2D broken up sheet structure having more edge sites. The BET surface areas for S@g-C3N4, 1.0, 2.0, and 3.0 wt% Fe3O4/FeS2 were 40, 109, 137 and 162 m2/g, respectively. Even though Fe3O4/FeS2 were incorporated into the nanosheet, the pore size was increased from 2.0 to 2.15 nm. S@g-C3N4 has an average band gap of 2.60 eV that decreased to 2.30, 2.21 and 2.18 eV at 1.0, 2.0 and 3.0 wt% of FeS2. In addition, Fe3O4/FeS2/g-C3N4 nanosheets showed an emission band at 460 nm. Moreover, the intensity of this band decreased as the content of Fe3O4/FeS2 reached 3.0 wt%. The rate of hydrogen production is accelerated as the percentage of Fe3O4/FeS2 increased from 1.0 to 3.0 wt%. The sample 3.0 wt% Fe3O4/FeS2 showed the best rate of hydrogen production (8480 mL/g·min).

Morphology control of high-quality hexagonal perovskite BaNiO3 by molten salt method

BaNiO3 single crystals with a hexagonal perovskite structure are prized for their exceptional Ni oxidation state and face-sharing structure, which grants them a high-performance potential as electrocatalysts. Despite their potential, obtaining high-quality morphology of BaNiO3 single crystals remains a challenge, making their characterization difficult and limiting their efficiency. In this study, we present a method for synthesizing high-quality BaNiO3 single crystals by morphology control using a molten salt method, which involves modifying the concentration of KOH, reaction time, and cooling rate. The optimal conditions for synthesizing high-quality BaNiO3 single crystals were found to be a reactant-to-KOH ratio of 1:50 and a reaction time of more than 3 h, which resulted in hexagonal-prism-shaped single crystals. However, using different reactant-to-salt ratios and shorter reaction times led to the formation of polycrystalline or pine-needle-shaped BaNiO3 along with secondary phases of BaCO3 and NiO. A higher KOH concentration required a longer reaction time, as the precursor diffusion rate slowed down. The average size of BaNiO3 single crystals increased as the cooling rate decreased, reaching the average width of ∼90 μm and the length of over 1 mm at the cooling rate of 5 °C/h. Our findings present optimal conditions for synthesizing a high-quality single-crystalline BaNiO3 with a hexagonal perovskite structure and could contribute to the development of BaNiO3 crystals for applications in ferroelectrics, photovoltaics, and chemical catalysis.

Fabrication and characterization of recyclable, magnetic (CoFe2O4)x/Ag2S-ZnO composites for visible-light-induced photocatalytic degradation of methylene blue dye

Magnetic (CoFe2O4)x/Ag2S-ZnO composites (where x = 0.25, 0.5, 0.75 and 1 wt% CoFe2O4) were successfully synthesised and investigated in the removal of methylene blue (MB) from aqueous medium under visible-light irradiation. X-ray diffraction (XRD) analysis confirmed the crystallinity of the as-synthesised materials and established the average crystal size of these materials to be <8.5 nm. Vibrating sample magnetometer (VSM) analysis confirmed that all cobalt ferrite doped nanocomposites exhibited ferrimagnetic behavior with saturation magnetization values varying from 6.55 to 40.52 emu/g being recorded. Near complete degradation (99 %) was attained when 1 gL−1 of (CoFe2O4)0.5/Ag2S-ZnO composite was added to a 10 ppm solution of methylene blue (MB) at neutral pH for 4 h of visible light irradiation. The catalyst showed good stability, removing 93.1 % of MB dye after five reuse cycles. The composite catalyst reported in this study is therefore a promising material for large-scale water and wastewater treatment processes.

Cooling Crystallization of Paracetamol in a Slug-Flow Crystallizer with Silicone Oil as Continuous Phase

Continuous tubular crystallizers that can provide high yield and better control of crystal size would be of great interest to the industrial crystallization process. However, most continuous crystallizer designs face challenges either due to surface fouling or crystal breakage. In this paper, we explore the ability of slug-flow cooling crystallizers to continuously generate acetaminophen crystals using silicone oil as the continuous phase. Each slug acts as a crystallizer, and the crystals formed inside the dispersed phase avoid encrustation. Three crystallizer configurations were studied at a wide range of supersaturation and flow rates. It was found that a narrow crystal size distribution can be achieved at high flow rates and high supersaturation. Additionally, the average crystal size and the crystallization yield increased with supersaturation and residence time. The configuration of the tubular crystallizer was found to influence the crystallization yield by affecting the internal mixing in the slugs. With further studies, slug-flow cooling crystallizer can be developed for continuous crystallization of crystals with a narrow size distribution, polymorphic purity, and good yield.

Effect of pre-sintering temperatures on the thermoelectric properties and decoupling mechanism of conductivity and Seebeck coefficient in modified Sr0.89La0.1TiO3

Thermoelectric materials convert thermal energy into electrical energy; therefore, they can be potentially used for waste heat recovery from high-temperature metallurgical slag or as spacecraft energy generators. However, the effect of the pre-sintering temperature during the preparation of these materials on their thermoelectric properties has not been examined yet. In this study, a simple two-step sintering method is used to produce La-doped strontium titanate and decouple the Seebeck coefficient from the conductivity through a pre-sintering step, thereby improving its thermoelectric performance, and explore the influence of the pre-sintering temperature on the sample particle size. The obtained results indicate that increasing the pre-sintering temperature can simultaneously increase the material conductivity and Seebeck coefficient, thereby decoupling these two parameters and significantly improving the power factor. After pre-sintering at 900 °C, the maximum conductivity reaches 7830 S/m, and ZT reaches the maximum value of 0.12. This effect is achieved by increasing the average crystal size while reducing the number of grain boundaries during pre-sintering.

Solvothermal synthesis of CMTS quaternary semiconductor nanoparticles with a symmetric kesterite structure: The role of the autoclave filling factor

Copper manganese tin sulfide (CMTS) is one of the promising chalcogenide materials and a potential candidate as an absorber material to develop low-cost, ultrathin solar cells. CMTS (Cu2MnSnS4) quaternary semiconductor nanoparticles (NPs) were synthesized by a solvothermal method utilizing different autoclave filling ratios. The influence of the autoclave filling ratio on the structure, phase formation, morphology, composition and optical properties of the CMTS-NPs was studied using various experimental techniques. The autoclave was filled with a solution up to 50, 60 and 70 percent of the autoclave volume. According to the FESEM images, the CMTS-NPs are uniform, dense and spherical, with slight agglomeration. The CMTS particles have an average crystal size in the range of 31 to 40 nm for different autoclave filling ratios. The chemical composition for CMTS was obtained from SEM – EDX and it was found that the sample with 60% filling factor had the best structure, with the atomic percentages of Cu: 26%, Mn: 9%, Sn: 12%, and S: 53%, which are close to the optimal values. The XRD results showed that the composition of the product was close to the stoichiometry of CMTS, with a Kesterite structure. Investigation of different autoclave filling factors showed that 60% is an optimum filling rate to obtain the CMTS pure phase with high crystallinity. The CMTS particles had a broad absorption band in the whole visible range with a band gap of 1.38 eV, being promising for photovoltaic applications.

A new spectrophotometric method for sensing promethazine hydrochloride in its pharmaceutical formulation and in biological fluids using copper nanoparticles (CuNPs)

A new, simple, and sensitive spectroscopic method has been developed for the determination of PMH in its pure form, in its pharmaceutical formulation, and in biological fluids (blood and urine) spectrophotometrically using copper nanoparticles (CuNPs) synthesized by the green method as a colorimetric detector without the use of chemical reagents. This method was characterized by being easy, sensitive, inexpensive, and environmentally friendly. A colored product (PMH-CuNPs) was formed. The absorbance was measured at the wavelength of 641.4 nm, and the linear range of (20–280) μg/ml, and it was found that the value of the correlation coefficient was (0.9983), the detection limit was (0.39) μg/ml, the quantitative limit was (1.18) µg/ml, and the molar absorption coefficient was (1315.69) L/mol. cm and Sandell significance were (0.2439) µg/cm&lt;sup&gt;2&lt;/sup&gt;, the average value of the percent recovery was 100.4%. The method was successfully applied to estimate Promethazine. HCL (PMH) in its pharmaceutical formulation and in biological fluids, and the characteristics of the colored product (PMH-CuNPs) were diagnosed. By measuring with several techniques, the average diameter was 73.54 nm in AFM technique, and the average crystal size through the XRD technique was 58 nm. SEM was measured, and the complex particles appeared in a spherical or semi-spherical shape, with an average size of 71.89, 82.04, and 79.25. FTIR was measured, and the functional groups were determined.

Biosynthesis of silver nanoparticles from Arum dioscoridis plant leaf aqueous extract: anticancer and antimicrobial properties

This study was carried out to synthesize silver nanoparticles (AgNPs) from Arum dioscoridis (AD) leaf extract and to investigate the cytotoxic and antipathogenic effects of them. The plant material had a reducing and stabilizing effect on the synthesized nanomaterial. During the plant-mediated synthesis of nanomaterials, no substances that would cause environmental pollution were used. For the structural characterization of AD-AgNPs, Ultraviolet-visible (UV-vis) Spectroscopy, Field Emission Scanning Electron Microscopy (FE-SEM), Electron Dispersive X-ray (EDX) Spectroscopy, Fourier Transform Infrared (FT-IR) Spectroscopy, Transmission Electron Microscopy (TEM), X-ray Diffractometer (XRD), Atomic Force Microscopy (AFM) and Zetasizer analyses were performed. The produced AgNPs showed maximum surface plasmon resonance at 431.67 nm and had mostly spherical morphology. The zeta potential value of the nanomaterial was -9.76 mV and the average powder crystal size was 31.48 nm. The minimum inhibitory concentration (MIC) values (mg/L) of AD-AgNPs on Staphylococcus aureus, Escherichia coli, Bacillus subtilis, Pseudomonas aeruginosa, and Candida albicans were 0.25, 2.00, 0.125, 4.00, and 1.00, respectively. After 24 and 48 hours of application by MTT [3-(4,5-dimetiltiazol-2-il)-2,5-difeniltetrazolium bromid] assay, the half-maximal inhibitory concentrations (IC50: μg/mL) of AD-AgNPs on human colon adenocarcinoma cell (CACO-2), human breast cancer cell (MCF-7), glioblastoma multiforme cell (T98-G), and healthy human umbilical vein endothelial cell (HUVEC) lines were determined as 2.977, 2.801, 5.694, 4.392; 2.115, 2.300, 2.612, 4.091, respectively.

Synthesis of novel MnFe2O4/BiOI green nanocomposite and its application to photocatalytic degradation of tetracycline hydrochloride: (LC-MS analyses, mechanism, reusability, kinetic, radical agents, mineralization, process capability, and purification of actual pharmaceutical wastewater)

Antibiotics in water bodies pose a serious threat to public health and the environment, leading to increased efforts to eliminate them from wastewater. In this study, a green nanocomposite catalyst of MnFe2O4/BiOI and Calendula officinalis was evaluated for its ability to decompose tetracycline in simulated sunlight. Characterization techniques including DRS, DLS, VSM, FTIR, XRD, TEM, FESEM, EDX, LC-MS, and pHpzc were used, revealing MnFe2O4/BiOI 's average crystal size of 14.47 nm, band gap of 1.7 eV, and magnetic saturation of 23.63 emu/gr. Under optimal conditions of a pH level of 9, tetracycline concentration of 20 mg/L, MnFe2O4/BiOI dosage of 0.5 g/L, and a reaction time of 200 min, the MnFe2O4/BiOI catalyst effectively broke down tetracycline, resulting in complete degradation. The pseudo-first-order equation accurately predicted degradation rates, and reusability tests showed only a 5% drop in efficiency after six cycles. The recommended method achieved high mineralization rates, with COD and TOC elimination efficiencies of 83.04% and 61.45%, respectively. Maximum removal efficiency for TOC and COD in pharmaceutical wastewater was achieved after 200 min, with 44.73% and 57.19%, respectively. Under optimal conditions, with 20 mg/L of tetracycline and sunlight exposure, the maximum tetracycline removal rate was 76.02%. This study demonstrated that the MnFe2O4/BiOI catalyst-based Xenon-photocatalytic approach is effective and adaptable for treating wastewater containing antibiotics from drug production and manufacturing processes.

Engineering of Defective MOF-801 Nanostructures within Macroporous Spheres for Highly Efficient and Stable Water Harvesting.

Water harvesting using the metal-organic framework (MOF)-801 is restricted by limited working capacity, powder structuring, and finite stability. To overcome these issues, wecrystallized MOF-801 on the surface of macroporous poly(N-isopropylacrylamide-glycidyl methacrylate) spheres, called P(NIPAM-GMA), through an in situ confined growth strategy, forming spherical MOF-801@P(NIPAM-GMA) composite with temperature-responsive function. By lowering the nucleation energy barrier, the average size of the MOF-801 crystals decreased by 20 times. Thus, abundant defects as adsorption sites for water couldbe installed in the crystals lattices. As a consequence, the composite provides an unprecedented high water harvesting efficiency. The composite wasproduced in the kilogram-scale and can capture 1.60kg H2 O/kg composite/day from 20% RH between 25°C and 85°C. This work provides an effective methodology for improving the adsorption capacity through controlled defects formation as adsorption sites and to improve the kinetics through the design of a composite with macroporous transport channel network. This article is protected by copyright. All rights reserved.

Novel Synthesis of MXene/CeCr2O4 Nanocomposite and its Optimistic Characterizations for Energy Storage Applications

Novel nanocomposite MXene/CeCr2O4 had been synthesized by means of inexpensive co-precipitation method. This paper reports the smooth nanocomposite of MXene/CeCr2O4 by co-precipitation method and the sol–gel route used for spinel cerium chromite (CeCr2O[Formula: see text] nanoparticles in which ethylene glycol chemical is exploited to restrain the accumulation of nanoparticles. The results show the formation of small nanoparticles with an average crystal crystalline size of CeCr2O4, MXene, MXene/CeCr2O4 nanocomposite is 37.9[Formula: see text]nm, 18.4[Formula: see text]nm, 11.15 nm, respectively. Characterizations, such as the X-ray diffraction (XRD), have demonstrated the amorphous nature of nanocomposite. The structural morphology [scanning electron microscopy (SEM)] shows the formation of nanocomposite with average particle size of[Formula: see text]nm of about 0.59[Formula: see text]nm. Raman spectroscopy shows that chemical bonding, energy dispersive spectroscopy (EDS) and photoluminance spectroscopy were performed and 3.56[Formula: see text]eV is band gap energy calculated from UV spectra. A comprehensive peak was noticed at 1425[Formula: see text]cm[Formula: see text] because of bending and stretching oscillations of O–H groups and zeta potential value[Formula: see text]19.1[Formula: see text]mV. All of these results confirmed the successful formation of nanocomposite of MXene/CeCr2O4. The resulting MXene/CeCr2O4 nanocomposite structure shows evidence of significant characteristics as compared to single material having much potential for numerous applications such as optical, energy storing and conductive applications.

Synthesis of g-C3N4@WO3 nanocomposites for dye adsorptive removal in water medium: Equilibrium and kinetics studies

In this research, WO3, g-C3N4, and g-C3N4@WO3 nanocomposites were synthesized from Na2WO4.2H2O and urea precusors via the hydrothermal method in a strong acid medium. Physico-chemical characteristics of WO3, g-C3N4, and g-C3N4@WO3 nanocomposites were examined by means of XRD, Raman, FTIR, FE-SEM, BET, and UV-Vis spectroscopy. The produced materials were then applied for studying adsorptive removal of methylene blue (MB) as a model pollutant from aqueous solutions. The results showed that g-C3N4@WO3 nanocomposites were successfully synthesized, with a hexagonal shape and an average crystal size of in the range of 15.4–20.7 nm. The surface area (68.3 m2/g) of g-C3N4@WO3 nanocomposites was 2.37 times higher compared to sole WO3, and g-C3N4@WO3 composites were mesoporous materials with a typical average pore diameter of 4.5 nm. It was revealed that the MB adsorption process occurred extremely quickly, reaching equilibrium after only about 20 min, with a maximum uptake of MB of 190 mg/g which was significantly higher than other adsorbents. The adsorption process was followed the first-order-kinetics model and the adsorbent showed high durability in adsorbing MB, with a slight decline in adsorption efficiency after 4 cycles (from 98.7% to 95.9%). This research provides an easy method for producing high adsorption capacity nanocomposite which can be applied for efficient removal of MB from water.

Struvite Got by a Modified Technology as the Basis of an Environmentally Friendly Controlled-release MgNP-fertilizer

The results of a quantitative analysis of nutrients based on samples of struvite as a controlled release nitrogen-phosphorus fertilizer, obtained using two technology options, were presented. It was shown that the use of traditional struvite deposition technology leads to the formation of a coarse-grained product (average crystal size 578 μm). It was confirmed that the modified technology allows to obtain highly dispersed struvite (average crystal size 19 μm) with a more extended particle surface and an ammonium content of 98–99% of the theoretical value with a higher nutrient release rates compared to struvite got by conventional technology. Struvite synthesized by the modified technology was found to show improved performance as a controlled release MgNP fertilizer.

Preparation and Characterization of Ultrafine SnO2 Nanoparticles as Anode Materials in Lithium Ion Batteries

In this work, ultrafine SnO2 nanoparticles were prepared by a facile solvothermal route using SnCl4.5H2O as initial materials. Phase compositions and microstructures of as-prepared nanoparticles have been investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), and the particle size analyzer. It was found that the obtained ultrafine SnO2 nanoparticles with the good dispersibility exhibited a pure rutile structural phase with an average crystal grain size of 7.4 nm. The electrochemical performance was characterized by cyclic voltammetry, galvanostatic cycling, and electrochemical impedance spectroscopy (EIS). The galvanostatic cycling results at a current density of 100 mAh.g-1 showed that as-prepared SnO2 nanoparticles possess a high specific discharge capacity of 1379 mAh∙g-1 with a Coulombic efficiency of 57% at the first cycle, this efficiency was over 91% after the 5th cycle, and the specific discharge capacity of 276 mAh∙g-1 was maintained during the 50th cycle of discharge/charge. Despite the relatively low cyclic stability, the effectve electrochemical performance of the SnO2 electrode due to its ultrafine nanostructure expanded active regions and promoted the reversible process of lithium insertion/extraction.

Synthesis of CaCO3/Cu2O/GO Nanocomposite Catalysts for Hydrogen Production from NaBH4 Methanolysis

The synthesis of CaCO3/Cu2O/GO nanocomposites was developed by sol-gel auto-combustion method. The analysis of structure was completed on X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, and environmental scanning electron microscopy (ESEM). The XRD spectra of the nanocomposites matched the crystal structure of CaCO3/Cu2O. The average crystal size was 20 nm for Cu2O and 25 nm for CaCO3 nanoparticles. FTIR data showed the absorption bands of Cu2O and GO. Raman spectroscopy data confirmed the formation of GO sheets. ESEM micrographs displayed spherical nanoparticles dispersed in GO sheets. X-ray photoelectron spectroscopy showed the peaks of Cu 2p, O 1s, C 1s, Cu 3s, and Ca 2p. The spectra of optical absorption revealed an absorption band of around 450 nm. The calcium content increase led to a decrease in the optical energy gap from 2.14 to 1.5 eV. The production of hydrogen from NaBH4 across the methanolysis reaction was accelerated by the CaCO3/Cu2O/GO nanocomposites. Therefore, these nanocomposites are superior in catalytic hydrogen production systems.