Influence Of Surface Area Research Articles

Supported H8PV5Mo7O40 on activated carbon: Synthesis and Investigation of influencing factors for catalytic performance.

Polyoxometalates (POMs), in particular the Keggin-type HPA-5 (H8PV5Mo7O40) are widely established as effective catalysts for acid- and redox-catalyzed reactions. Yet, they are mainly used as homogeneous catalysts, which poses challenges regarding catalyst separation. This study explores the synthesis of supported HPA-5, and its application as a heterogeneous catalyst for biomass conversion, focusing on activated carbons with diverse chemical and physical properties as support materials. Characterization of these carbons gives insights into the influence of surface area, oxygen content, and acidity on HPA adsorption and stability. Activated carbon CW20, was found to be the best support due to its high vanadium loading and effective preservation of the HPA-5 structure. It underwent various pre- and post-treatments, and the obtained supported catalysts were evaluated for their catalytic performance in converting glucose under both oxidative (OxFA process) and inert (Retro-Aldol condensation) conditions. Notably, HPA-5 supported on CW20 emerged as an exceptional catalyst for the retro-aldol condensation of glucose to lactic acid, achieving a selectivity of 15% and a conversion rate of 71%, with only minimal vanadium leaching.

Revisiting the Roles of Carbon in the Catalysis of Lithium–Sulfur Batteries

Carbon materials are the key hosts for the sulfur cathode to improve the conductivity and confine the lithium polysulfides (LiPSs) in lithium–sulfur batteries (LSBs), owing to their high electronic conductivity and strong confinement effect. However, physical or chemical trapping methods have limitations in preventing the dissolution and accumulation of LiPSs in the electrolyte. Catalysis has emerged as a fundamental solution to accelerate the sluggish redox kinetics, and carbon materials acting as catalyst supports or direct catalysts significantly impact the reaction efficiency. Herein, the roles of carbon in the catalysis of LSBs are systematically discussed, focusing on the influence of surface area, pore structure, and surface chemistry on sulfur conversion. Then, two modification strategies, vacancy defects and heteroatom doping, that endow carbon with catalytic activity are summarized. Finally, the remaining challenges and solutions are outlined in terms of the preparation and characterization of the functional carbon in LSBs. This perspective provides essential insights and guidance for the rational design of carbon‐based catalysts in LSBs.

Microwave Pyrolysis of Biomass: The Influence of Surface Area and Structure of a Layer

The paper presents the results of experimental research into lab-scale microwave pyrolysis of wood biomass. The influence of the surface area and the structure of the biomass layer on the characteristics of pyrolysis during microwave heating are discussed. We have established that the biomass layer structure and surface area have a significant effect on the yield of pyrolysis gas. The approach of creating artificial deformation of the biomass layer was tested. The elements of artificial porosity made it possible to increase the CO yield by 18% and 32% compared to the pyrolysis of a biomass layer with artificial channels and a uniform layer, respectively. The concentration of H2 was 33% higher compared to the layer without artificial pores and 3% lower compared to artificial channels. The yield of CO2 increased by 25%, and the yield of CH4 doubled. The experiments showed that the distribution of biomass on a half of the bottom of the crucible and the additional porosity of the biomass layer surface effectively increase the yield of the pyrolysis gas components. Recommendations for increasing the efficiency of microwave pyrolysis of biomass were formulated.

Analisis Materi Ajar Konsep Laju Reaksi Pada Buku Teks Kimia SMA/MA

Penelitian ini bertujuan untuk: (1) mendeskripsikan kesesuaian konsep laju reaksi pada materi ajar kimia SMA/MA kelas XI terhadap kurikulum 2013, (2) mendeskripsikan struktur makro dalam materi ajar kimia SMA/MA kelas XI pada konsep laju reaksi, dan (3) mendeskripsikan proposisi apa saja yang berpotensi kesalahan konsep yang terdapat dalam materi ajar kimia SMA/MA kelas XI pada konsep laju reaksi. Penelitian ini merupakan jenis penelitian deskriptif. Objek penelitian ini yaitu: (1) Buku teks kimia SMA/MA kelas XI. Data yang diperoleh dianalisis secara deskriptif. Susunan makro wacana laju reaksi pada buku teks A pembahasan konsep dimensi elaborasi mencapai level 4 dan dimensi progresi terdapat 4 konsep pada level 2. Susunan makro wacana laju reaksi pada buku teks B pembahasan konsep dimensi elaborasi mencapai level 4 dan dimensi progresi terdapat 5 konsep pada level 2. Proposisi yang berpotensi kesalahan konsep pada buku teks A yaitu penjelasan katalis dan tetapan laju reaksi. Proposisi yang berpotensi kesalahan konsep pada buku teks B yaitu pada rumus molaritas, penulisan koefisien reaksi, penjelasan pengaruh luas permukaan, penjelasan grafik orde reaksi 0, orde reaksi 1, orde reaksi 2, orde reaksi -2, dan orde reaksi ½.

Pyrocatalytic oxidation - strong size-dependent poling effect on catalytic activity of pyroelectric BaTiO3 nano- and microparticles.

Pyrocatalysis is an emerging advanced oxidation process for wastewater remediation with the potential for thermal energy harvesting and utilization. Although several studies explored the potential of new pyrocatalyst materials to degrade harmful organic water pollutants, the role of important material properties and electric poling procedures on the pyrocatalytic activity is still unclear. In this work, we investigate the interdependence between particle size, electric poling and pyrocatalytic activity of BaTiO3 powders with nominal particle sizes of 100, 200 and 500 nm by using the dichlorofluorescein redox assay. Depending on the particle size, the influence of surface area or phase composition on the pyrocatalytic activity predominates. Moreover, we demonstrate that poling of pyrocatalysts leads to a strong size-dependent increase of pyrocatalytic activity. This poling effect increases with particle size up to +247% and can be explained with size-dependent changes in phase composition and domain structure. Combining all results, the progression of the pyrocatalytic activity as a function of particle size was derived and a future strategy for maximizing the catalytic performance of pyrocatalysts was developed. This study greatly improves the understanding about the role of important material properties and electric poling on pyrocatalytic activity, thus enabling an effective catalyst design. With the help of highly active catalysts, the pyrocatalytic process can take the next step in its development into a new and energy-efficient advanced oxidation process for water remediation.

Electrochemical reduction of CO2 on activated copper: Influence of surface area

In this work, we investigate the effect of activation (thermal or electrochemical) on the electrochemically active surface area (determined from under potential deposition of lead) and its influence on the electrochemical reduction of CO2. The copper samples were characterized by XPS (X-ray photoelectron spectroscopy) and XRD (X-ray diffraction) before and after activation, and after performing electrochemical CO2 reduction experiments on them. The investigations suggest that the electrochemical reduction of CO2 takes place on metallic copper and the higher currents typically observed for activated copper is a manifestation of increased surface area. The specific method of oxidation does not seem to influence the electrochemical reduction of CO2, and only marginal differences compared to pristine copper were observed. Nonetheless, a definite change in selectivity of the reduction products was observed for activated copper foils compared to bare copper foil.

Viscoelastic Behavior, Curing and Reinforcement Mechanism of Various Silica and POSS Filled Methyl-Vinyl Polysiloxane MVQ Rubber

The role of Aerosil silicas, A90, R812, R812s on the complex dynamic viscosity η* of methyl-vinyl polysiloxane MVQ at processing temperature 80°C was analyzed based on experiments with a torsional rheometer Rubber Process Analyzer RPA. The influence of surface area and surface activity on the Payne’s effect was determined by oscillating rheometer Ares G2. The decrease in complex modulus G* by increasing strain for silicas R812, R812s was mostly due to the breaking down of filler-filler networking, the modification of surface led to better processability resulting in the increase of tensile strength TS, from 0.42 MPa unfilled silicone to 9.31 MPa MVQ containing R812. Higher surface activity of silica A90 caused a decrease in filler networking due to a better filler-polymer interactions, which resulted in the increase of the percentage of non-covalent crosslinks determined for samples treated with ammonia. The decrease of static water contact angle θ of silicone rubber after incorporation of A90 was observed. Influence of allylisobutylPOSS on curing, crosslink density, static and dynamic behavior of silicone rubber was considered.

Crystal Structure‐ and Morphology‐Driven Electrochemistry of Iron Oxide Nanoparticles in Hydrogen Peroxide Detection

AbstractVarious iron oxide nanoparticles with different morphologies are synthesized and subsequently tested for their conductivity and electrocatalytic activity toward hydrogen peroxide. The morphology and chemical and phase composition of iron oxide nanoparticles are evaluated employing scanning electron microscopy, X‐ray diffraction, 57Fe Mössbauer spectroscopy, and Brunauer–Emmett–Teller specific surface area measurements. The electrochemical properties of the as‐prepared sensors are estimated by electrochemical impedance spectroscopy. It is found that α‐Fe2O3 nanoparticles with the sticks morphology exhibit the best conductivity response among all the tested phases and morphologies. Moreover, it is predicted that conductivity of different iron oxides can be connected with a number of vacancies in their crystal structure. Furthermore, the influence of surface area and porosity of the material on the conductivity can be omitted. Finally, the electrocatalytic activity of iron oxide nanoparticles toward hydrogen peroxide is confirmed by means of cyclic voltammetry. The obtained results perfectly reflect those derived from electrochemical impedance spectroscopy and indicate that glassy carbon electrodes modified with the sticks morphology of α‐Fe2O3 hold a huge potential for hydrogen peroxide detection.

Relationship of Coke Reactivity and Critical Coke Properties

The gasification reactions of five metallurgical cokes were studied using a thermogravimetric analyzer at 1273 K and 1673 K in CO2-CO-N2 gas mixture. The results show that these cokes showed different reactivities in the gasification reactions. Properties that potentially influence coke reactivity including ash content, catalytic index, surface area, and crystallite size were measured and correlated with reactivity. The results indicate that reactivity had a good correlation with ash content, catalytic index, and crystallite size. The effect of surface area on coke reactivity was marginal. Coke reactivity was positively affected by catalytic index but inversely affected by ash content. Although crystallite size inversely affected reactivity, the reaction rate at the initial stage was more predominantly influenced by the mineral matter. Therefore, the influence of surface area and crystallite size was overshadowed by the impact of ash content and catalytic index at the initial stage of reaction.

(Invited) Solar-Driven Chemical Conversion Using Silicon Photoelectrochemical Cells

Solar-driven chemical conversion using photoelectrochemical (PEC) cells has attracted intense interests to produce value-added chemical fuels and feedstock using solar energy. In particular, silicon is attractive for a photoelectrode since it’s earth-abundant and low cost, and has small bandgap to absorb most of solar spectrum. However, silicon suffers from slow kinetics for PEC reactions such as water splitting and CO2 reduction and also from severe corrosion during the operation. In this talk, I’ll present our strategies to develop a high performance and stable silicon-based PEC cells. Firstly, I’ll discuss the light-matter-chemical interaction occurring on a photoelectrode’s surface and demonstrate that PEC reactions are coupled with light abosorption and electrocatalysis bound on the surface of a photoelectrode. Based on these understanding, I’ll present our approaches to maximize light absorption and electrocatalysis in PEC cells (1) by using locally defined 3-dimensional cocatalysts and (2) by using a transparent cocatalysts on Si photoelectrodes. Influences of surface area and coverage of cocatalysts as well as charge transport properties of Si photoelectrodes will be presented using water oxidation reaction as a model chemical reaction. I’ll also show that these approaches can be applicable to CO2 reduction reactions.

A modified heteropoly acid catalyst with cetyltrimethylammonium bromide for methacrolein to methacrylic acid

A novel type of heteropolyacids, CTAB-CsH3PMo11VO40 (CTA-CsPAV), was developed by a method of emulsion synthesis using cetyltrimethyl ammonium bromide (CTAB) as the structure promoter, which was applied as a catalyst in the oxidation of methacrolein (MAL) to methacrylic acid (MAA) with fixed-bed reactor. The structure and property of CTA-CsPAV were characterized by FT-IR, XRD, nitrogen adsorption-desorption, NH3-TPD, SEM, XPS, and so on. The structure-performance relationship of CTA-CsPAV was systematically studied, wherein the influence of surface area, acidity, redox property of CTA-CsPAV were focused and discussed. Importantly, the long-term performance of CTA-CsPAV was also investigated.

The migration of heavy metal elements during pyrolysis of oil shale in Mongolia

The migration of trace elements during the pyrolysis of Mongolian oil shale is studied at the macroscopic (the porosity change) and microscopic (the occurrence state) levels. Four groups of oil shale (904, 1054, 10513 and 10807) in the Dalai Bulang mining area of Mongolia were studied. Oil shale samples were heated in a tube furnace in argon atmosphere. Final temperatures of pyrolysis varied from 300 °C to 900 °C resulting in different char. The content of eight kinds of heavy metal elements in the oil shale and the pyrolysis semi-coke were determined by inductively coupled plasma mass spectometry (ICP-MS), through which the distribution and the migration of these elements were analyzed. The specific surface area and pore distribution of different semi-coke were detected by specific surface area analyzer. The influence of surface area and pore distribution on heavy metal element migration was investigated. The sequential chemical extraction (SEC) was carried out on the original oil shale samples. Trace elements in different occurrence models were also detected by ICP-MS. Then the relationship between occurrence models and trace element migration during pyrolysis was also analyzed. The results show that: 1) The concentrations of heavy metal elements in four kinds of oil shale groups are similar, and the occurrence models of the same kind of heavy metal elements in four samples are also similar. 2) The migration amount of Zn and Cu is small at the temperature below 500 °C, while both of the elements escaped rapidly at the temperature above 700 °C. Because Zn and Cu are mainly present in the carbonate which decomposed rapidly at the temperature above 600 °C. 3) The mobility of most of the elements in the sample shows a downward trend during 500–600 °C and 800–900 °C. During these temperature ranges the specific surface area of the semi-coke was increased, because the elements was reabsorbed by the semi-coke.

Influence of the structure of polymer fiber composites on the analysis of the zeta potential

ABSTRACTThis article addresses the questions about the influence of surface area, roughness, and sample mounting on the zeta potential analysis. A series of knitted yarns and fabrics of cotton and modacryl and their blends represent a real‐life model system to study these effects. The combination of the natural cotton and the man‐made modacryl makes possible to study the effect of the different origin for surface and interfacial charge and the surface area‐weighted contributions to the average zeta potential of a chemically heterogeneous composite material. In our study, two measuring cells of the SurPASS electrokinetic analyzer were used, namely the Cylindrical Cell and the Adjustable Gap Cell. Comparison of the results obtained in two different measuring cells was related to the measured material. We used the Cylindrical Cell for both the zeta potential analysis of yarn and knitted fabrics and compared these results with data obtained for knitted fabrics using the Adjustable Gap Cell. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46227.

Highly sensitive formaldehyde gas sensor based on hierarchically porous Ag-loaded ZnO heterojunction nanocomposites

In this paper, a convenient solution combustion method to synthesis hierarchically porous Ag-loaded ZnO heterojunction nanocomposites with various Ag contents was reported. The analysis of X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and Brunauer-Emmett-Teller (BET) nitrogen adsorption-desorption were conducted to characterize the ingredients, microstructure and surface morphology. Ag and ZnO show separate phases due to the reduction of Ag+ and the faster crystallization rate of ZnO. The as-synthesized powders were used as gas sensing materials to fabricate gas sensors. The gas-sensing performance was tested towards 100ppm formaldehyde at an optimum operating temperature of 240°C and Ag-loaded ZnO (with the different Ag atomic ratio) based gas sensors showed a superior gas-sensing performance comparing with pure ZnO. Especially 1 at% Ag-loaded ZnO has the highest gas response as 170.42. The possible gas-sensing mechanism was discussed in this paper. For example, the influence of surface area, the formation of heterostructure, Ag elements, adsorbed oxygen and so on.

The influence of surface area, porous structure, and surface state on the supercapacitor performance of titanium oxynitride: implications for a nanostructuring strategy.

A recent surge of interest in metal (oxy)nitride materials for energy storage devices has given rise to the rapid development of various nanostructuring strategies for these materials. In supercapacitor applications, early transition metal (oxy)nitrides have been extensively explored, among which titanium oxynitride stands out due to its great potential for charge storage. Despite recent advances in supercapacitors based on titanium oxynitride, many underlying factors governing their capacitive performance remain elusive. In this work, nanostructured titanium oxynitride is prepared by firing an organic-inorganic hybrid precursor under a hot ammonia atmosphere, and the influence of its physical characteristics on the supercapacitor performance is investigated. New insights into the effects of surface area, porous structure, and surface state of titanium oxynitride on the supercapacitor performance are revealed through which a comprehensive understanding about the capacitive behavior of titanium oxynitride is provided. In addition, the implications of these insights for a nanostructuring strategy striving for higher capacitance and improved stability are discussed.

Scale effect on springback behavior of pure titanium foils in microbending at elevated temperature

The occurrence of size effects in microforming process influences the accuracy of the products significantly. To investigate the scale effect and the mechanism of springback behavior of thin pure titanium (Ti) foils bent at elevated temperatures, scaled microbending processes assisted by resistance heating are performed for the foils with different thickness of 0.02, 0.05, and 0.1mm. It is found that the springback angle increases with decreasing foil thickness at room temperature. However, after bending at elevated temperatures, the springback angle is found to decrease with decreasing foil thickness. Due to the lower flow stress of surface, the influence of surface area is thought to be the dominating factor that results in the less springback of thinner foils at elevated temperatures. To confirm this and to predict the springback angles at elevated temperatures, a new theoretical model of surface area increasing with increasing temperature is proposed. The springback angles are calculated by theoretical analysis using conventional plastic theory and the proposed model. As temperature increases, the large reduction of springback angles compared to 298K can be captured by using the proposed model successfully. The validity of the proposed model is confirmed.

Mesoporous In2O3 materials prepared by solid-state thermolysis of indium-organic frameworks and their high HCHO-sensing performance

Mesoporous In2O3 materials were synthesized by calcining indium-organic frameworks (InOFs, CPM-5 and MIL-68), which were further successfully utilized to detect toxic HCHO vapor. By taking the intrinsic structural features of two InOF precursors into account, the surface areas of produced indium oxides were well investigated via controlling the calcination temperature. The influence of surface area on the gas sensing performance was studied in detail. Porous In2O3 prepared by heat treatment at 650°C showed the highest responses to 50ppm HCHO (Rg/Ra=31.8 and 38.0, respectively; Rg, resistance in gas; Ra, resistance in air) at 210°C, which surpass the values of all the reported In2O3 materials to date under the similar conditions. The promising HCHO-sensing properties enable these InOF-templated mesoporous In2O3 materials to be competitive candidates for detecting poisonous formaldehyde in practice.

Behavior of graphitized carbon blacks in the electrodegradation and sorption of chlorophenoxyacetic acids

This paper compares the properties of two graphitized carbon blacks in the sorption and first stage of electrodegradation (dechlorination) of chlorophenoxyacetic acids and discusses the influence of surface area on the electrochemical behavior of these carbon materials. Two carbon blacks with ten-fold different surface areas (100 and 10 m2/g) were used as sorbents and electrode materials as received. Two chloroorganics with various numbers of Cl atoms in the molecule, 4-chlorophenoxyacetic acid and 2,4-dichlorophenoxyacetic acid, were adsorbed on the carbon samples from neutral aqueous electrolyte solutions containing low concentrations of adsorbate. Cyclovoltammetric studies of the graphitized carbon blacks were performed using powdered electrode techniques, and the drop in organics concentration during cyclization was measured using HPLC. For carbon black with a smaller surface area, the presence of faradaic reactions was not masked by capacitive currents, and well-shaped faradaic couple peaks characteristic of a quinine/hydroquinone-like adsorbed system were observed. This indicates that these materials are active in chloroorganics electrodegradation (by dechlorination). The extent of electrodegradation (a four-fold drop in organics concentration) observed for carbon black with a larger surface area indicates the dominant role of surface (porosity) development in these processes.

Quick high-temperature hydrothermal synthesis of mesoporous materials with 3D cubic structure for the adsorption of lysozyme

Three-dimensional cage-like mesoporous FDU-12 materials with large tuneable pore sizes ranging from 9.9 to 15.6 nm were prepared by varying the synthesis temperature from 100 to 200 °C for the aging time of just 2 h using a tri-block copolymer F-127(EO106PO70EO106) as the surfactant and 1,3,5-trimethyl benzene as the swelling agent in an acidic condition. The mesoporous structure and textural features of FDU-12-HX (where H denotes the hydrothermal method and X denotes the synthesis temperature) samples were elucidated and probed using x-ray diffraction, N2 adsorption, 29Si magic angle spinning nuclear magnetic resonance, scanning electron microscopy and transmission electron microscopy. It has been demonstrated that the aging time can be significantly reduced from 72 to 2 h without affecting the structural order of the FDU-12 materials with a simple adjustment of the synthesis temperature from 100 to 200 °C. Among the materials prepared, the samples prepared at 200 °C had the highest pore volume and the largest pore diameter. Lysozyme adsorption experiments were conducted over FDU-12 samples prepared at different temperatures in order to understand their biomolecule adsorption capacity, where the FDU-12-HX samples displayed high adsorption performance of 29 μmol g−1 in spite of shortening the actual synthesis time from 72 to 2 h. Further, the influence of surface area, pore volume and pore diameter on the adsorption capacity of FDU-12-HX samples has been investigated and results are discussed in correlation with the textural parameters of the FDU-12-HX and other mesoporous adsorbents including SBA-15, MCM-41, KIT-5, KIT-6 and CMK-3.

Effects of various Carbonization Processes in the Preparation of Nanoporous Carbon Materials using Ipomoea Carnea Stem Waste for the Removal of Dyes from Textile Industrial Effluents

Nanoporous activated carbon materials were prepared from abundantly available Ipomoea Carnea stem waste. A series of five Nanoporous carbon samples were prepared by subjecting the carbon material to various chemical processes. The physico-chemical properties and adsorption capacities were compared. The adsorption capacity of selected derived carbon sample using Ipomoea Carnea stem waste prepared by Dolomite process was much greater than the capacities of the other carbons prepared by various processes viz., Acid process, ZnCl 2 process, Sulphate process and Carbonate process. The influence of surface area and porosity of the carbon samples on dye removal was analysed. The effects and influence of pKa values of dyes and isoelectricpoint (pH zpc ) of Nanoporous carbon materials were broadly studied and interpreted with dye adsorption onto Nanoporous carbon material. The results reveal that the prepared activated carbon could be employed as a lowcost alternative for removing toxic and carcinogenic dyes from the textile industrial waste water.