scholarly journals Gradually Fe-doped Co3O4 nanoparticles in 2-propanol and water oxidation catalysis with single laser pulse resolution.

2022 ◽  
Author(s):  
Swen Zerebecki ◽  
Kai Schott ◽  
Soma Salamon ◽  
Joachim Landers ◽  
Eko Budiyanto ◽  
...  
Keyword(s):  
Particle Size ◽  
Laser Pulse ◽  
Surface Area ◽  
Active Sites ◽  
Surface Composition ◽  
Oxidation Catalysis ◽  
Colloidal Nanoparticles ◽  
Co3o4 Nanoparticles ◽  
X Ray ◽  
Cation Doping

Controlling the surface composition of colloidal nanoparticles is still a challenging yet mandatory prerequisite in catalytic studies to investigate composition-activity trends, active sites, and reaction mechanisms without superposition of particle size- or morphology-effects. Laser post-processing of colloidal nanoparticles has been employed previously to create defects in oxide nanoparticles, while the possibility of laser-based cation doping of colloidal nanoparticles without affecting their size, remains mostly unaccounted for. Consequently, at the example of doping iron into colloidal Co3O4 spinel nanoparticles, we developed a pulse-by-pulse laser cation doping method to provide catalyst series with gradual surface composition but maintained extrinsic properties such as phase, size, and surface area for catalytic studies. Laser pulse number-resolved doping series were prepared at laser intensity chosen to selectively heat the Co3O4-NPs to roughly 1000 K and enable cation diffusion of surface-adsorbed Fe3+ into the Co3O4 lattice while maintaining the spinel phase, particle size, and surface area. The combination of bulk-sensitive X-ray fluorescence (XRF) and surface-sensitive X-ray photoelectron spectroscopy (XPS) was used to confirm a surface enrichment of the Fe-dopant. XRD, Magnetometry, and Mössbauer spectroscopy revealed an increasing interaction between Fe and the antiferromagnetic Co3O4 with an increasing number of pulses, in line with a proposed laser-induced surface doping of colloidal Co3O4 with Fe. Using Fick’s second law the thermal diffusion-related doping depth was estimated to be roughly 2 nm after 4 laser pulses. At the example of gas-phase 2-propanol oxidation and liquid-phase oxygen evolution reaction, the activity of the laser-doped catalysts is in good agreement with previous observations on binary iron-cobalt oxides. The catalytic activity was found to linearly increases with the calculated doping depth in both reactions, while only catalysts processed with at least one laser pulse were catalytically stable, highlighting the presented method in providing comparable, active, and stable gradual catalyst doping series for future catalytic studies.

The role of oxygen vacancy over ZnCr-layered double oxide in enhancing solar light-driven photocatalytic degradation of bisphenol A

2018 ◽  
Vol 15 (4) ◽  
pp. 226 ◽  
Author(s):  
Meiqing Chen ◽  
Pingxiao Wu ◽  
Qianqian Wei ◽  
Yajie Zhu ◽  
Shanshan Yang ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Particle Size ◽  
Bisphenol A ◽  
Photocatalytic Degradation ◽  
Surface Area ◽  
Organic Pollutants ◽  
Oxygen Vacancies ◽  
Solar Light ◽  
X Ray ◽  
Vis Spectroscopy

Environmental contextAn important goal in attempts to degrade environmental organic pollutants is the development of a photocatalyst that is responsive to visible light. We report a facile method for preparing a zinc-based photocatalyst with oxygen vacancies that efficiently degrades bisphenol A under solar light irradiation. The study will stimulate further investigations into the efficacy of other metal oxide nanostructures for the photocatalytic degradation of organic pollutants. AbstractTwo ZnCr-layered double oxides (ZnCr-LDO) were fabricated via different thermal treatment of the ZnCr-layered double hydroxide (ZnCr-LDH) precursor. ZnCr-V-700 and ZnCr-A-700 were obtained at 700 °C under vacuum and air, respectively. As X-ray diffraction revealed, both ZnCr-V-700 and ZnCr-A-700 were made up of ZnO and ZnCr2O4 spinel, and ZnCr-V-700 displayed a lower crystallinity and many uniform particles with oxygen vacancies. Scanning electron microscopy and transmission electron microscopy revealed that the particle size of ZnCr-V-700 was ~30 nm and its disordered crystallinity suggested the existence of oxygen vacancies. Notably, the ZnCr-LDO materials showed remarkably enhanced photocatalytic activity compared to the ZnCr-LDH precursor. ZnCr-V-700 was the most active material and more than 90 % of BPA was degraded after irradiation for 200 min with high mineralisation (up to 37 %). The results of Brunauer–Emmett–Teller surface area analysis, X-ray photoelectron spectroscopy, Raman and UV-vis spectroscopy and electron paramagnetic resonance spectroscopy showed that oxygen vacancies incorporated into ZnCr-V-700 played a key role in improving the photocatalytic performance by enhancing interfacial charge transfer and restricting the charge recombination. In addition, the uniform particle size, larger surface area and the coexistence of ZnO and ZnCr2O4 also played a synergistic role. In conclusion, this work not only provides a facile and low-cost method to prepare photocatalysts for treatment of wastewater containing BPA, but also supplies a new idea for improving the performance of photocatalysts.

Preparation of Carbon-Encapsulated Fe Core-Shell Nanostructures by Confined Arc Plasma

2011 ◽  
Vol 688 ◽  
pp. 245-249 ◽  
Author(s):  
Zhi Qiang Wei ◽  
Xiao Yun Wang ◽  
Hua Yang
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Particle Size ◽  
Specific Surface ◽  
Surface Area ◽  
Core Shell ◽  
Arc Plasma ◽  
X Ray ◽  
The Core ◽  
Transmission Electron

Special carbon encapsulated Fe core-shell nanoparticles with a size range of 15–40 nm were successfully prepared via confined arc plasma method. The composition, morphology, microstructure, specific surface area, particle size of the product by this process were characterized via X-ray diffraction (XRD), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), X-ray energy dispersive spectrometry (XEDS) and BET N2adsorption. The experiment results shown that the carbon encapsulated Fe nanoparticles with clear core-shell structure, the core of the particles is body centered cubic (BCC) structure Fe, and the shell of the particles is disorder carbons. The particle size of the nanocapsules ranges from 15 to 40nm，with an averaged value about 30nm, the particles diameter of the core is about 16nm and the thickness of the shells is about 6-8 nm, and the specific surface area is 24 m2/g.

scholarly journals Study of oxygen evolution reaction on thermally prepared xPtOy-(100-x)IrO2 electrodes

2020 ◽  
Vol 10 (4) ◽  
pp. 347-360
Author(s):  
Ollo Kambiré ◽  
Lemeyonouin A. G. Pohan ◽  
Konan H. Kondro ◽  
Lassiné Ouattara
Keyword(s):  
Surface Area ◽  
Oxygen Evolution ◽  
Photoelectron Spectroscopy ◽  
Oxygen Evolution Reaction ◽  
Active Sites ◽  
Platinum Oxide ◽  
Basic Medium ◽  
X Ray ◽  
Tafel Slopes ◽  
Ohmic Drop

The mixed coupled xPtOy-(100-x)IrO2 electrodes (x = 0, 10, 20, 30, 40, 50, 60, 70, 80, 90 and 100) were thermally prepared at 450 °C on titanium supports. The prepared electrodes were firstly physically characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Afterwards, electrochemical characteri­zations were performed by voltammetric (cyclic and linear) methods in different electrolyte media (KOH and HClO4). It is shown that the prepared electrodes are composed by both PtOy (platinum and platinum oxide) and IrO2 (iridium dioxide). For xPtOy-(100-x)IrO2 electrodes having higher content of IrO2, more surface cracks and pores are formed, defining a higher surface area with more active sites. Higher surface area due to presence of both PtOy and IrO2, is for xPtOy-(100-x)IrO2 electrodes in 1 M KOH solution confirmed by cyclic voltammetry at potentials of the oxide layer region. For all prepared electrodes, voltammetric charges were found higher than for PtOy, while the highest voltammetric charge is observed for the mixed 40PtOy-60IrO2 (x = 40) electrode. The Tafel slopes for oxygen evolution reaction (OER) in either basic (0.1 M KOH) or acid (0.1 M HClO4) media were determined from measured linear voltammograms corrected for the ohmic drop. The values of Tafel slopes for OER at PtOy, 90PtOy-10IrO2 and IrO2 in basic medium are 122, 55 and 40 mV dec-1, respectively. For other mixed electrodes, Tafel slopes of 40 mV dec-1 were obtained. Although proceeding by different OER mechanism, similar values of Tafel slopes were obtained in acid medium, i.e., Tafel slopes of 120, 60 and 39 mV dec-1 were obtained for PtOy, 90PtOy-10IrO2 and IrO2, and 40 mV dec-1 for other mixed electrodes. The analysis of Tafel slope values showed that OER is more rapid on coupled mixed electrodes than on pure PtOy. For mixed xPtOy-(100-x)IrO2 electrodes, OER is more rapid when the molar percent of PtOy meets the following condition: 0 ˂ x ≤ 80. This study also showed that the mixed coupled electrodes are more electro­cata­lytically active for OER than either PtOy or IrO2 in these two media. 

Nanostructured TiO2 modified by perfluoropolyethers: Gas phase photocatalytic activity

2010 ◽  
Vol 25 (1) ◽  
pp. 96-103 ◽  
Author(s):  
Claudia L. Bianchi ◽  
Silvia Ardizzone ◽  
Giuseppe Cappelletti ◽  
Giuseppina Cerrato ◽  
Walter Navarrini ◽  
...  
Keyword(s):  
Gas Phase ◽  
Surface Area ◽  
Photoelectron Spectroscopy ◽  
Surface Composition ◽  
High Surface ◽  
Ammonium Phosphate ◽  
Water Contact ◽  
Electronic Band ◽  
X Ray ◽  
Bet Analysis

A high-molecular-weight perfluoropolyether (PFPE-YR) and a perfluoropolyether containing ammonium phosphate (PFPE-F10) have been evaluated as fluorinated coating for high-surface-area titanium oxides. Coated nano-TiO2 shows hydrophobic properties and excellent buoyancy on water. In addition to photoactivity toward the degradation of toluene in gas phase, specific trial analyses have been completed to estimate the modified titanium oxide features. Brunauer–Emmett–Teller (BET) analysis for the surface area determination, ultraviolet-visible spectroscopy (UV-Vis) for the material electronic band gap, high-resolution transmission electron microscopy (HRTEM), x-ray diffraction (XRD), and x-ray photoelectron spectroscopy (XPS) for the morphology, structure, and surface composition, respectively, and water contact angle and infrared (IR) analysis have been performed to estimate the wettability and stability of coated titanium.

Anaerobic vs. aerobic preparation of silicon nanoparticles by stirred media milling. The effects of dioxygen, milling solvent, and milling time on particle size, surface area, crystallinity, surface/near-surface composition, and reactivity

RSC Advances ◽  
2016 ◽  
Vol 6 (113) ◽  
pp. 112370-112380
Author(s):  
Eric V. Bukovsky ◽  
Karlee P. Castro ◽  
Brent M. Wyatt ◽  
Olga V. Boltalina ◽  
Steven H. Strauss
Keyword(s):  
Particle Size ◽  
Surface Area ◽  
Silicon Nanoparticles ◽  
Milling Time ◽  
Surface Composition ◽  
Near Surface ◽  
Media Milling ◽  
Attritor Milling

Silicon nanoparticles milled anaerobically in heptane or mesitylene are smaller and much more reactive than SiNPs milled aerobically in the same solvents for equal attritor milling times.

scholarly journals Co Loading Adjustment for the Effective Obtention of a Sedative Drug Precursor through Efficient Continuous-Flow Chemoselective Hydrogenation of 2-Methyl-2-pentenal

Catalysts ◽  
2021 ◽  
Vol 12 (1) ◽  
pp. 19
Author(s):  
Antonio Jesús Fernández-Ropero ◽  
Bartosz Zawadzki ◽  
Krzysztof Matus ◽  
Wojciech Patkowski ◽  
Mirosław Krawczyk ◽  
...  
Keyword(s):  
Particle Size ◽  
Surface Area ◽  
Photoelectron Spectroscopy ◽  
Continuous Flow ◽  
Hydrogen Adsorption ◽  
Bet Surface Area ◽  
Sedative Drug ◽  
X Ray ◽  
Chemoselective Hydrogenation ◽  
Temperature Programmed

This work presents the effect of Co loading on the performance of CNR115 carbon-supported catalysts in the continuous-flow chemoselective hydrogenation of 2-methyl-2-pentenal for the obtention of 2-methylpentanal, an intermediate in the synthesis of the sedative drug meprobamate. The Co loading catalysts (2, 6, 10, and 14 wt.%) were characterized by Brunauer–Emmett–Teller (BET) surface area analysis, transmission electron microscopy (TEM), H2 temperature-programmed reduction (H2-TPR), temperature-programmed desorption of hydrogen (H2-TPD) analysis, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy for selected samples, and have been studied as hydrogenation catalysts at different pressure and temperature ranges. The results reveal that a certain amount of Co is necessary to achieve significant conversion values. However, excessive loading affects the morphological parameters, such as the surface area available for hydrogen adsorption and the particle size, preventing an increase in conversion, despite the increased presence of Co. Moreover, the larger particle size, caused by increasing the loading, alters the chemoselectivity, favouring the formation of 2-methyl-2-pentenol and, thus, decreasing the selectivity towards the desired product. The 6 wt.% Co-loaded material demonstrates the best catalytic performance, which is related to the formation of NPs with optimum size. Almost 100% selectivity towards 2-methylpentanal was obtained for the catalysts with lower Co loading (2 and 6 wt.%).

scholarly journals MECHANOCHEMICAL SYNTHESIS OF CALCIUM TITANATE AND RESEARCH OF ITS PHOTOCATALYTIC ACTIVITY

2018 ◽  
Vol 59 (6) ◽  
pp. 83 ◽  
Author(s):  
Konstantin V. Ivanov ◽  
Alexandr V. Agafonov ◽  
Olyga V. Alexeeva
Keyword(s):  
Particle Size ◽  
Photocatalytic Activity ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Biological Tissues ◽  
Calcium Titanate ◽  
Ceramic Technology ◽  
X Ray Diffraction ◽  
X Ray

Recently much attention is paid to the synthesis and study of the properties of inorganic materials, based on alkaline earth titanates with a perovskite structure that have various polymorphic forms depending on the temperature. Calcium titatanat (CaTiO3) can be selected from the variety of perovskites because of its relatively high dielectric constant, unique photochemical properties, chemical stability, and compatibility with biological tissues, which leads to its application in microelectronics, photocatalysis and biomedicine as bone implants. In this paper, a solid-phase synthesis of calcium titanate was carried out by ceramic technology using mechanochemistry methods. This method allows to obtain calcium titanate directly by mechanochemical activation from the initial mixture of Ca (OH)2 and TiO2, which significantly reduces the energy consumption for its production. Structural changes in the synthesized material during calcination at 120 °C, 200 °C, 400 °C, 600 °C, and 800 °C were studied. The particle size and specific surface area of powders synthesized and calcined at 800 °C was measured by laser diffraction ("Analysette 22") and the low temperature (77K) nitrogen adsorption-desorption vapor, respectively. The phase composition of the obtained materials was studied by X-ray diffraction. It was found on the basis of studies of the particle size distribution that synthesized and calcined powders contain nanoparticles with sizes of 377 and 422 nm. The samples of CaTiO3 calcined at 120 °C and 800 °C have a mesoporous structure, the specific surface area was 46 and 7 m2/g, respectively, and average pore size in powders was 4 nm. It was found by the X-ray diffraction technique that the uncalcined sample contains admixtures of CaCO3 and TiO2 that can be removed completely at 600 °C.The photocatalytic activity of the synthesized material has been studied by the example of Rhodamine B dye decoloration on the calcium titanate calcined at 800°C. It was found that the decomposition degree of dye in solution was 77% for 80 min at a 6.7% shadow adsorption.

Effects of Wet Grinding Process on the Properties of the Ground Diatomite Particles

2010 ◽  
Vol 178 ◽  
pp. 124-128
Author(s):  
Xu Ming Wang ◽  
Yan Xi Deng ◽  
Yan Feng Li
Keyword(s):  
Methylene Blue ◽  
Particle Size ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Grinding Process ◽  
X Ray Diffraction ◽  
X Ray ◽  
Wet Grinding ◽  
Grinding Time

Wet grinding of diatomite was carried out in a stirred mill. The changes in particle size, specific surface area and structure or the particle shape in the wet grinding process were investigated. The adsorption of methylene blue from aqueous solution by the ground diatomite was also studied. X-ray diffraction (XRD), scanning electron microscopy (SEM) and IR spectra were employed to characterize the ground diatomite. The median particle size decreased and the specific surface area increased with the grinding time, an agglomeration phenomenon was not observed during the experimental grinding time. The X-ray diffraction patterns versus grinding time showed that a peak intensity reduction of opal. The results of adsorption of methylene blue onto diatomite indicated the adsorption capacity increases with the increase of grinding time until eventually reaches a constant value.

scholarly journals Magnesium Impregnated on NaX Zeolite Synthesized from Cogon Grass Silica for Fast Production of Fructose via Microwave-Assisted Catalytic Glucose Isomerization

Catalysts ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 981
Author(s):  
Sittichai Kulawong ◽  
Saran Youngjan ◽  
Pongtanawat Khemthong ◽  
Narong Chanlek ◽  
Jatuporn Wittayakun ◽  
...  
Keyword(s):  
Surface Area ◽  
Photoelectron Spectroscopy ◽  
Active Sites ◽  
Nitrate Solution ◽  
Conventional Heating ◽  
X Ray ◽  
Nax Zeolite ◽  
Microwave Assisted ◽  
Glucose Isomerization ◽  
Mg Content

Fructose is a crucial intermediate in the production of several chemical platforms. Fructose is mainly produced from glucose isomerization either through immobilized enzymes or heterogeneous catalysts using a conventional heating source, and this is time-consuming. Thus, this work discloses a fast production of fructose via microwave-assisted catalytic glucose isomerization using Mg catalysts supported on NaX zeolite from cogon grass silica. The catalysts were prepared by the impregnation of magnesium nitrate solution and subsequently transformed into MgO on NaX by calcination. The effect of 3, 6 and 9 wt.% Mg content on NaX on the performance of glucose isomerized to fructose was tested at 90 °C for 15 min. The best catalyst was selected for studying the effect of reaction times of 5, 15, 30 and 60 min. Results from X-ray diffraction (XRD), N2 sorption and CO2 temperature-programmed desorption (CO2-TPD) suggested that crystallinity, surface area and micropore volume decrease but basicity increases with Mg content. The X-ray photoelectron spectroscopy (XPS) result confirmed the presence of mixed phases of MgO and Mg2CO3 in all catalysts. The glucose conversion enhanced with the Mg loading but the fructose yield gave the highest value with Mg of 6 wt.%, probably due to the tuning of high active sites and surface area. The greatest fructose selectivity and yield (71.9% and 25.8%) were obtained within 15 min by microwave-assisted catalytic reaction, shorter than the reported value in the literature, indicating a suitable reaction time. Mg (6 wt.%)/NaX catalyst preserves the original catalytic performance up to three cycles, indicating that it is a promising catalyst for fructose production.

scholarly journals Modification of Carbon Black with Hydrogen Peroxide for High Performance Anode Catalyst of Direct Methanol Fuel Cells

Materials ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 3902
Author(s):  
Yu-Wen Chen ◽  
Han-Gen Chen ◽  
Man-Yin Lo ◽  
Yan-Chih Chen
Keyword(s):  
Particle Size ◽  
Carbon Black ◽  
Surface Area ◽  
Functional Groups ◽  
Methanol Oxidation ◽  
Photoelectron Spectroscopy ◽  
Direct Methanol Fuel Cells ◽  
Reducing Agent ◽  
Precipitation Method ◽  
X Ray

In this study, high-surface-area carbon black is used to support PtRu. In order to increase the functional groups on the surface of carbon black and to have a more homogenous dispersed PtRu metal, the surface of carbon black is functionalized by H2O2. PtRu/carbon black is synthesized by the deposition–precipitation method. NaH2PO2 is used as the reducing agent in preparation. These catalysts are characterized by N2 sorption, temperature-programmed desorption, X-ray diffraction, transmission electron microscope, and X-ray photoelectron spectroscopy. The methanol oxidation ability of the catalyst is tested by cyclic voltammetry measurement. Using H2O2 to modify carbon black can increase the amount of functional groups on the surface, thereby increasing the metal dispersion and decreasing metal particle size. NaH2PO2 as a reducing agent can suppress the growth of metal particles. The best modified carbon black catalyst is the one modified with 30% H2O2. The methanol oxidation activity of the catalyst is mainly related to the particle size of PtRu metal, instead of the surface area and conductivity of carbon black. The PtRu catalyst supported by this modified carbon black has very high activity, with an activity reaching 309.5 A/g.

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