Brunauer Emmett Teller Studies Research Articles

Flexible Solid-State Aqueous Sodium-Ion Capacitor Using Mesoporous Self-Heteroatom-Doped Carbon Electrodes

Supercapacitors find numerous applications such as in consumer electronics, peak power demands, capturing surge power, etc. Various types of carbon materials are explored as electrode material. In this work, disordered mesoporous carbon was synthesized from expired medicinal capsule covers by sulfonation and subsequent chemical activation was carried out with KOH. Powder X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, Brunauer–Emmett–Teller studies, and X-ray photoelectron spectroscopy were utilized to characterize the generated carbon which confirmed the disordered carbon had a large surface area with stratified pores. The testing for electrochemical charge storage was conducted on a three-electrode setup comprising an aqueous 1 M NaClO4 electrolyte that exhibited a high 324 F g–1 specific capacitance at 0.4 A g–1, revealing suitability for sodium-ion ultracapacitor. Consequently, CR2032 coin-type sodium-ion capacitors were fabricated using both aqueous and nonaqueous electrolytes. The laboratory prototype capacitor with the aqueous electrolyte delivered 42 Wh kg–1 specific energy at 179 W kg–1 specific power. Besides, the capacitor with the nonaqueous electrolyte showed a remarkable 54.3 Wh kg–1 specific energy at 540 W kg–1 specific power. The Coulombic efficiency exhibited by both devices was about 99% even at the 10000th charge–discharge cycle. The amplified charge storage performance of the disordered carbon was ascribed to the presence of homogeneous mesopores that led to enhanced accessibility of the electrode/electrolyte contact area. According to the results of the power law and Dunn’s approach, the mesoporous carbon electrode was found to have a considerable diffusive charge storing mode involving Na+ intercalation in the sodium-ion nonaqueous ultracapacitor. A green-light-emitting diode could run continuously for 16 min on a single charge using the laboratory prototype CR-2032 coin-type nonaqueous ultracapacitor. Interestingly, a homemade solid-state flexible sodium-ion ultracapacitor was also fabricated that impressively manifested 13.7 Wh kg–1 specific energy at 180 W kg–1 specific power in 180° bent angle.

Modification of Electrospun CeO2 Nanofibers with CuCrO2 Particles Applied to Hydrogen Harvest from Steam Reforming of Methanol.

Hydrogen is the alternative renewable energy source for addressing the energy crisis, global warming, and climate change. Hydrogen is mostly obtained in the industrial process by steam reforming of natural gas. In the present work, CuCrO2 particles were attached to the surfaces of electrospun CeO2 nanofibers to form CeO2-CuCrO2 nanofibers. However, the CuCrO2 particles did not readily adhere to the surfaces of the CeO2 nanofibers, so a trace amount of SiO2 was added to the surfaces to make them hydrophilic. After the SiO2 modification, the CeO2 nanofibers were immersed in Cu-Cr-O precursor and annealed in a vacuum atmosphere to form CeO2-CuCrO2 nanofibers. The CuCrO2, CeO2, and CeO2-CuCrO2 nanofibers were examined by X-ray diffraction analysis, transmission electron microscopy, field emission scanning electron microscopy, scanning transmission electron microscope, thermogravimetric analysis, and Brunauer-Emmett-Teller studies (BET). The BET surface area of the CeO2-CuCrO2 nanofibers was 15.06 m2/g. The CeO2-CuCrO2 nanofibers exhibited hydrogen generation rates of up to 1335.16 mL min-1 g-cat-1 at 773 K. Furthermore, the CeO2-CuCrO2 nanofibers produced more hydrogen at lower temperatures. The hydrogen generation performance of these CeO2-CuCrO2 nanofibers could be of great importance in industry and have an economic impact.

Superparamagnetic hematite spheroids synthesis, characterization, and catalytic activity

The leaf extract of Muntingia calabura is being first reported to be used for the synthesis superparamagnetic hematite nanoparticles by following the green-chemistry approach. Field Emission – Scanning Electron Microscopic image revealed the formation of irregular nano spheroids averaging at 48.57 nm in size and characteristic of Fe and O atoms, as revealed by Energy Dispersive X-Ray spectrum. X-ray diffraction analysis results proved the crystallinity of hematite diffraction planes with crystallite sizes averaging at 30.68 nm. The lattice parameter values stayed concordant with the literature. The superparamagnetic nature was attested by the high value of saturation magnetism (2.20 emu/g) with negligible coercivity and retentivity. Fourier Transform Infrared Spectroscopy results affirmed numerous moieties involved in the synthesis of hematite nanoparticles and the existence of signature Fe–O bands. Thermogravimetric analysis studies portrayed the thermal behavior nanoparticles with 28% weight loss and thermal stability was attained after 700 °C. X-ray photoelectron spectroscopy analysis confirmed the valence states of Fe and O in the hematite nanoparticles and ascertained the purity. The mesoscopic structure was revealed by Brunauer–Emmett–Teller studies with considerable surface area (112.50 m2/g). The Fenton-like catalysis mediated by the nanoparticle sample was demonstrated by degrading methylene blue dye. The remarkable degradation efficiency of 93.44% was obtained and the kinetics was conformed to a second-order model with a high R2 value. Therefore, the highly crystalline and mesoporous superparamagnetic hematite spheroids prepared using the leaf extract of M. calabura would find promising applications in various catalysis processes.

Hydrogen generation by methanol steam reforming process by delafossite-type CuYO2 nanopowder catalyst

Due to global warming, the energy crisis, and climate change, hydrogen is to be used as an alternate renewable energy source. In industry, hydrogen generation is mainly obtained by the natural gas steam reforming reaction. In this study, delafossite CuYO 2 nanopowder was used as a catalyst for methanol steam reforming (MSR). The delafossite-structured CuYO 2 nanopowder was synthesized by the glycine nitrate process, annealed in N 2 , and used for MSR. The influences of different annealing temperatures on the phase transformation, surface area, and crystal structure composition of the Cu–Y–O powder were examined. The characteristics of the CuYO 2 nanopowder were identified by X-ray diffraction studies, Brunauer-Emmett-Teller studies (BET), field emission scanning electron microscopy studies, transmission electron microscopy, and X-ray photoelectron spectroscopy. The BET studies indicated that the surface area of the CuYO 2 nanopowder varied from 2 to 16 m 2 /g before and after annealing at different temperatures because of structural transformation. Scanning electron microscopy of the CuYO 2 nanopowder revealed a porous structure formed by the large amount of gas released during the glycine-nitrate process. Moreover, when the self-combusted nanopowder was annealed in N 2 at 750 °C, the porous structure of the CuYO 2 nanopowder was retained. The CuYO 2 catalyst in MSR performance was estimated, and the hydrogen generation rate reached as high as 1735.65 ml STP min −1 g-cat −1 at 300 °C without reduction treatment. Besides, the CuYO 2 catalyst exhibit a higher hydrogen production rate at a lower temperature. The hydrogen generation performance of this CuYO 2 catalyst could be of great importance in industry and have a global economic impact. Hydrogen generation over the delafossite-Type CuYO 2 nanopowder catalyst. • CuYO 2 catalyst was prepared by a self-combusted glycine nitrate process. • CuYO 2 catalyst was applied for the methanol steam reforming. • The surface area of CuYO 2 powder varied from 2.9 to 16 m 2 /g. • The CuYO 2 exhibited hydrogen production rate as 1735.65 ml/min g-cat at 300 °C. • The CuYO 2 exhibit the higher hydrogen production rate at lower temperature.

Mesoporous metal oxide–α-Fe2O3 nanocomposites for sensing formaldehyde and ethanol at room temperature

The present study describes the synthesis of mesoporous metal oxide–α-Fe2O3 nanocomposites and investigation of their gas-sensing performance. Mesoporous Li2O-doped Fe2O3 and SnO2–Fe2O3 nanocomposites were synthesized employing a nanocasting technique using KIT-6 as the structure guiding template. The structural features of synthesized mesostructures were analyzed using X-ray diffraction, Brunauer–Emmett–Teller studies and Fourier transform infrared spectroscopy. The morphological features of metal oxide–Fe2O3 nanocomposites were observed by scanning electron microscopy and transmission electron microscopy. Thin films of mesoporous metal-oxide nanocomposites were prepared and studied as sensors toward formaldehyde (HCHO) and ethanol (C2H5OH) over the operating temperature range of 25–200 °C. The SnO2–Fe2O3 sensor showed maximum sensing response toward HCHO at 150 °C after attainment of sufficient ordering of structure at high temperatures. However, Li2O-doped Fe2O3 exhibited very high response of 6.08 and 5.82 for HCHO and C2H5OH, respectively, at room temperature (25 °C). Gas-sensing behaviors of nanocomposites along with the sensing phenomenon were explained on the basis of their mesostructures and crystallinity.

Titania-based porous nanocomposites for potential environmental applications

Titania–zeolite Y composites were synthesized by a facile solid-state dispersion method. The synergistic effects of porous zeolite structure and novel photocatalysis properties of titania nanoparticles were exploited. The physical properties of the composites were characterized by scanning electron microscopy, energy-dispersive X-ray, X-ray diffraction, diffuse reflectance spectroscopy, fourier transform infra-red spectroscopy and photoluminescence spectroscopy. Porosity and surface area of the composites were determined from Brunauer–Emmett–Teller studies. The antibacterial effect and the photocatalysis properties of these composites were studied. Composites exhibited higher growth reduction of Escherichia coli and Staphylococcus aureus as compared with the pure forms (P25 titania and zeolite Y). Maximum growth reduction of both types of bacterial cells (gram-positive as well as gram-negative) was observed with 20% titania–zeolite composite. The composite demonstrated 40 and 30% enhancement in the growth reduction of E. coli and S. aureus, respectively, as compared with the pure forms; 10% composite exhibited 50% enhancement in the photocatalysis efficiency of methylene blue dye degradation as compared with P25 titania nanoparticles and led to a complete removal of the dye in the first 60 min of photocatalysis process. Mechanisms for both applications have been proposed in light of the observed results.

Synthesis of mesoporous α-Fe2O3 nanostructures via nanocasting using MCM-41 and KIT-6 as hard templates for sensing volatile organic compounds (VOCs)

The work describes the synthesis of mesoporous α-Fe2O3 using two different forms of mesoporous silica MCM-41 and KIT-6 as hard templates employing nanocasting technique. The structural features of fabricated mesoporous α-Fe2O3 were studied using small angle X-ray scattering, X-ray diffraction and Fourier transform infrared spectroscopy. Surface properties of the oxides with porous morphology were studied by N2 sorption isotherms and Brunauer–Emmett–Teller studies, scanning electron microscopy and transmission electron microscopy. The mesoporous α-Fe2O3 oxides were then tested for detection of volatile organic compounds namely acetic acid, ethanol and formaldehyde. The α-Fe2O3 prepared from KIT-6 shows sensitivity of 45.21 towards acetic acid at temperature of 110 °C, much lower as compared to the temperatures reported in literature with short response and recovery times. The sensitivity obtained for acetic acid is over eight times higher than that for ethanol and formaldehyde making it a potentially selective sensor for acetic acid detection.

Influence of the reaction time on the physical–chemical and catalytic properties of vanadium phosphate catalysts prepared by a eutectic mixture

Vanadium phosphate (VPO) materials with high specific surface area prepared via a eutectic mixture as solvent and template with different lengths of time, i.e. 24, 72 and 144 h, were investigated in the oxidation of benzyl alcohol. The X-ray diffraction result indicated the initial VPO precursor was an amorphous phase due to the stronger incorporation of eutectic mixture. On subsequent reflux duration of 72 h, the precursor was composed of a crystallised VOHPO 4 ·H 2 O phase. On further reflux duration of 144 h, the incorporated eutectic mixture gradually was leached out and the precursor became more crystalline. Interestingly the N 2 adsorption–desorption measurements Brunauer–Emmett–Teller studies showed that the VPO precursor incorporated eutectic mixture was mesostructured and the specific surface area first increased then decreased with increasing the reflux duration time. The growth process of the VPO nanostructures formed in a eutectic mixture with different lengths of time was investigated by scanning electron microscopic analysis. The influence of calcination temperature and lengths of reflux duration on the activity and selectivity of the VPO catalyst was studied and discussed.

Correlation Between Morphology Control and Photocatalytic Performance of BiOBr Nano-Microstrutures

A systematic approach to optimize the photocatalytic activity of BiOBr nanoparticles was investigated and compared. The resulting BiOBr powders were successfully synthesized through two different pathways: stirred solvothermal and stirred hydrothermal processes under identical synthesis conditions of temperature and time. The composition, morphology, structure and optical properties of as-prepared samples were characterized by means of X-ray diffraction, scanning electron microscopy with energy dispersive X-ray spectroscopy, transmission electron microscopy, diffuse reflectance UV–Visible spectroscopy. Effective surface areas of the synthesized samples were estimated by Brunauer–Emmett–Teller studies. Catalysts prepared by solvothermal process and named (S-BiOBr) were of hierarchical microspheres, while the hydrothermally prepared ones called (H-BiOBr) were nanoflakes, both with a pure crystalline phase. The photocatalytic activities of as-synthesized structures were then examined to evaluate the effect of the synthetic route on the degradation of methyl orange (MO) dye as an organic compound model under simulated solar light irradiation (250 W Xenon lamp, 300 ≤ λ ≤ 800 nm). The photodegradation of MO was monitored by UV–Visible spectroscopy, substantiated by total organic carbon analysis. Hydrothermal process was a non-template method while in solvothermal route ethylene glycol has been used indicating the relative effects of the relationship of medium viscosity on morphology. On the basis of such analysis, the degradation efficiency of S-BiOBr towards MO was found to be 97% compared to 56% using H-BiOBr for 20 ppm concentration of dye. The kinetic analysis confirmed that the reaction rate constant kapp was nearly 3 times higher than that of H-BiOBr, suggesting that S-BiOBr displayed the highest photocatalytic activity for the effective decomposition of MO.

Kaolin-nano scale zero-valent iron composite (K-nZVI): synthesis, characterization and application for heavy metal removal

The present study explored the synthesis of Kaolin-nano scale zero-valent iron composite (K-nZVI) by using chemical reduction method. Sorption characteristics of the K-nZVI for the removal of Cu(II) ions was studied in batch conditions. The physical and chemical structure of the K-nZVI composite was characterized by Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-XRF), X-ray diffraction (XRD), Transmission electron microscopy (TEM) and Brunauer-Emmett-Teller studies (BET). The effect of pH, the initial metal ion concentration, and contact time on adsorption of Cu(II) onto K-nZVI was investigated. The K-nZVI exhibited good sorption performances over the initial pH range from 2.5 to 6.5. The kinetics data was studied by applying two sorption kinetic models (Pseudo-first and Pseudo-second-order) equations. The pseudo-second-order model was relatively suitable for describing the adsorption process. The equilibrium adsorption data is well fitted to Langmuir adsorption models. The maximum adsorption capacities of K-nZVI sorbent as obtained from Langmuir adsorption isotherm is found to be 178–200 mg g−1 for Cu(II). Sorption isotherm models (Langmuir and Freundlich) were applied to the experimental data. The adsorption kinetics was well represented by the pseudo second order rate equation, and the adsorption isotherms were better fitted by the Langmuir equation. The thermodynamic studies showed that the adsorption reaction of Cu(II) is endothermic processes. TheK-nVZI having number of features including easy preparation, environmentally friendly nature, low-cost and good sorption performance enable K-nZVI application in industrial purpose specifically in the field of industrial water treatment.

One-pot synthesis of three bismuth oxyhalides (BiOCl, BiOBr, BiOI) and their photocatalytic properties in three different exposure conditions

AbstractBiOCl, BiOBr, and BiOI have been synthesized by wet chemical route using bismuth nitrate (Bi(NO3)3.5H2O) and potassium halides, KCl, KBr, and KI, using a mixture of de-ionized water and ethanol as the solvent. Synthesized samples were characterized by X-ray diffraction and high-resolution SEM to observe the crystalline phase and crystallite size. Effective surface areas of the synthesized samples were estimated by Brunauer–Emmett–Teller studies. Photoactive properties of these samples were studied under three types of light exposure conditions viz. UV light from mercury vapour lamp, natural sunlight, and visible radiations from a 100-W incandescent tungsten filament. Degradation of methyl orange (MO) in aqueous media was estimated spectrophotometerically in visible range from the area under the curve with a peak at 464 nm. Kinetic constant for degradation reaction was calculated assuming the pseudo-first-order degradation mechanism. It was revealed that all the three samples show excellent degrada...

The fabrication and characterization of novel carbon dopedTiO2 nanotubes, nanowires and nanorods with high visible light photocatalytic activity

Novel carbon doped TiO2 nanotubes, nanowires and nanorods were fabricated by utilizing the nanoconfinement ofhollow titanate nanotubes (TNTs). The fabrication process included adsorption of ethanolmolecules in the inner space of TNTs and thermal treatment of the complex in inertN2 atmosphere. The structural morphology of carbon dopedTiO2 nanostructures can be tuned using the calcination temperature. X-ray diffraction, Ramanand Brunauer–Emmett–Teller studies proved that the doped carbon promoted thecrystallization and phase transition by acting as nucleation seeds. X-ray photoelectronspectroscopy (XPS) showed that O–Ti–C and Ti–O–C bonds were formed in thenanostructures. Additional electronic states from the XPS valence band due to carbon dopingwere observed. This evidence indicated the electronic origin of the band gap narrowing andvisible light absorption. The differences in chemical and electronic states between the surfaceand bulk of as-prepared samples confirmed that carbon was doped into the lattice ofTiO2 nanostructure through an inner doping process. The as-prepared catalysts exhibitedenhanced photocatalytic activity for degradation of toluene in gas phase under both visibleand simulated solar light irradiation compared with that of commercial Degussa P25. Thisnovel fabrication approach can valuably contribute to designing nanostructuredphotocatalytic materials and modifying various nanotube materials.