Specific Surface Area Of Composite Research Articles

Exploring the influence of KOH electrolyte concentration on the electrochemical properties of Co3O4-GO nanocomposite

In this study, we investigate the electrochemical performance of Co3O4-GO nanocomposite, synthesized via a hydrothermal method, as a function of electrolyte concentration. XRD, Raman, SEM, TEM, XPS, and BET techniques have been employed to examine the structural, microstructural, chemical states, and specific surface area characteristics of the composite material. According to SEM micrographs, the aggregated particles have a sheet-like morphology, and these sheets have been assembled into clusters. Using N2-adsorption/desorption isotherms, the pore volume, diameter, and specific surface area of composite were determined to be 0.24 cm3/g, 15 nm, and 63 m2/g, respectively. Based on cyclic voltammograms (CVs) recorded at different scan rates and electrolyte concentrations, the working electrode demonstrated pseudocapacitance behavior. The specific capacitance (Cs) of the fabricated electrode was estimated from GCD curves recorded at different current densities and electrolyte concentrations. For 1 M KOH solution, Cs of the composite electrode is found to be 258 F/g at 1 A/g, and this value drops to 222 F/g at 5 A/g. Furthermore the composite electrode's Cs decreases with increasing electrolyte concentration at a specific current density. The study indicates that 1 M of KOH electrolyte is the optimal electrolyte concentration for optimal energy storage.

Synthesis of MoO3 (1D) @SnO2 (2D) core-shell heterostructures for enhanced ethanol gas sensing performance

In this paper, MoO3 (1D) @SnO2 (2D) core-shell heterostructures were synthesized by a simple two-step hydrothermal method for ethanol gas sensor. The porous SnO2 nanosheets were uniformly coated on the surface of MoO3 nanorods, increasing the specific surface area of composite. The MoO3 nanorods act as an electron transport channel and play a bridging role between SnO2 nanosheets, facilitating the transfer of electrons and increasing the base resistance of sensors. The highest response of MoO3@SnO2 (Mo:Sn = 0.9:1) at the optimum operating temperature (200 °C) to 100 ppm ethanol was 48.64, approximately 12 times higher than that of MoO3 (4.04) and 7.8 times higher than that of SnO2 (6.23). In addition, MoO3@SnO2 heterostructure (Mo:Sn = 0.9:1) shows a fast response-recovery, good selectivity and excellent stability among all composites. The test results of UV-Vis, XPS, EPR, UPS and PL illustrated that the enhanced gas sensing mechanism of MoO3@SnO2 was ascribed to its high active sites, narrow band gap, and abundant surface vacancies.

Indium Oxide–Graphene Composites Prepared by the Sol–Gel Process and Single-Electrode Gas Sensors on Their Base

Indium oxide–graphene composites (containing 0–6.0 wt % graphene) were manufactured by the sol–gel process. The phase composition, microstructure, and gas-sensitive properties of the prepared materials were studied. The composites consist of isolated In2O3 and graphene phases, where graphene is predominantly adsorbed on the surfaces of indium oxide grains (the indium oxide grain sizes are 8–11 nm). The nanocomposites are distinguished by an enhanced sensitivity to both reducing gases (CH4, acetone) and oxidative gases (NO2). A far greater enhancement is in the sensory response to oxidative gases. Presumably, the major factors influencing the sensory properties of the composite are the high defectiveness of In2O3 and graphene phases, higher specific surface areas of composites compared to those of individual In2O3, and the likely formation of p–n junctions in the indium oxide and graphene contact zone. Graphene additives to indium oxide can improve the main performances (sensory response, response time, and recovery time) of single-electrode semiconductor sensors.

Incorporating Fe, Co co-doped graphene with PDI supermolecular for promoted photocatalytic activity: A story of electron transfer

Iron-cobalt dual single-atom anchoring on nitrogen-doped graphene (FexCoy-NG) improves the efficiency of migration and separation of photo-generated carriers. In this work, the perylene diimide (PDI) is self-assembled on the FexCoy-NG to form the FexCoy-NG/PDI composites by π-π interaction, which is reported for the first time. The bisphenol A (BPA) degradation of optimized 20% Fe0.2Co0.8-NG/PDI are nearly 100%, and the degradation rate is 1.5 and 12.7 times that of the self-assembled PDI and commercial-grade PDI. The high degradation performance by FexCoy-NG/PDI are mainly due to: (i) regulating the proportion of Fe-Co dual active sites content, so that it can achieve the synergistic interaction to facilitate the transfer of electrons in the catalytic reaction. (ii) PDI is uniformly dispersed by adding the FexCoy-NG, which increases the specific surface area of composites to adsorb more pollutants. Free radical trapping experiments and electron spin-resonance spectroscopy characterization confirmed that the O2–, OH, 1O2 and h+ are the main reactive species (RSs) for BPA degradation. Under the attack of RSs, BPA completes the processes of hydroxylation, demethylation, aromatization, ring-opening, and finally complete mineralization into CO2 and H2O. These results revealed that Fe0.2Co0.8-NG/PDI photocatalysts may be efficiently applied for the remediation of phenol contaminated natural waters.

Solar driven photocatalytic dye degradation through the novel Ti2C– ZnCo2O4MXenes nanocomposite

Two-dimensional (2D) zinc cobalt oxide (ZnCo2O4) has considerable promise material for efficient dye photocatalytic degradation. A novel family of two-dimensional anisotropic carbides and nitrides from early transition metals (MXenes) is particularly fascinating among 2D materials, such as graphene, due to their potential uses in electronics, medicine, and photo-catalysis. The extended Ti2C phases were created by synthesizing them from their parent Ti2AlC MAX phases under the same circumstances as the traditional acidic aluminum extraction procedure. However, due to its limited specific surface area and high carrier recombination rate, photo-catalytic performance is usually inadequate. Preparation, morpho-structural characterization, band gap measurement, and congo red photo-degradation potential of Ti2C MXene and three nano-composites made up of MXene enhanced by ZnCo2O4 are presented in this study. SEM images revealed hill like agglomerated rough microstructure with round shape many particles morphology. The experimentally obtained band gaps using Tauc's approach are in the 2.60–2.84 eV range. In recent years, the approach of photo-catalytic breakdown of contaminants employing semiconductor photo-catalysts with UV–visible light has grown in importance. The addition of ZnCo2O4 boosted the establishment of strong interfacial coupling between Ti2C and ZnCo2O4, shortening the route of carrier transfer and promoting the direct transfer of photo-generated electrons from Ti2C's valence band to ZnCo2O4.The specific surface area of composites increased significantly at the same time, which was beneficial for improving the UV-absorption capability of Ti2C composites. This research proposes a practical design method for increasing the degrading performance of 2D photo-catalysts, which may serve as a technical suggestion for the modification design of additional photo-catalysts. The MXene based nano-composites revealed high activity in the congo-red photo-degradation reaction (56%–78% of degraded congo-red after 270 min). Ti2C(97%)/ZnCo2O4(3%) composite showed an enhanced efficiency for degradation of congo-red.

Preparation of a novel composite photocatalyst BiOBr/ZIF-67 for enhanced visible-light photocatalytic degradation of RhB

In the preparation process of a novel composite photocatalyst BiOBr/ZIF-67, BiOBr prepared by one-step hydrothermal synthesis was used as the base material, and ZIF-67 was attached to the surface of BiOBr by the one-pot method; a series of BiOBr/ZIF-67 composite photocatalysts were prepared by changing the ratio of ZIF-67. Through X-ray diffraction (XRD) and other characterization methods, the prepared composites were systematically analyzed, the visible-light photocatalytic activity of which for the degradation of Rhodamine B (RhB) was studied, and a possible photocatalytic mechanism was proposed. It can be concluded from the experiment that BiOBr/ZIF-67(30%) with the best photocatalytic activity could degrade 95.2% of RhB, which is 50% higher than pure BiOBr. The prepared BiOBr/ZIF-67 was inferred to be a direct Z-Scheme heterojunction photocatalyst, which possessed intimately contacted interface and well-aligned straddling energy-band structures. In this visible-light heterojunction photocatalysts, ZIF-67 increased the specific surface area of composites, which was propitious to bring improved photocatalytic performance.

Pyrolysis temperature and feedstock affected Cr(VI) removal capacity of sulfidated zerovalent iron: Importance of surface area and electrical conductivity

Herein, feedstock (pinewood, rice straw, and dairy manure) and pyrolysis temperature (300, 500, and 700 °C) were selected as the influencing factors of properties of biochar (BC) to identify the contribution of biochar's matrix on Cr(VI) removal by BC-supported sulfidated zero-valent iron (S-ZVI/BC). Results showed that higher temperature was more conducible to improve the electrochemical properties and specific surface areas of composites. Raman spectra of S-ZVI supported by pinewood-derived BC (S-ZVI/PBC) showed the ID/IG ratio increased from 0.639 to 0.975 for the composites prepared at 300–700 °C, indicating the increased structural defects and resulting in the greatest Cr(VI) removal (35.81 mg g−1) and reduction (30.21 mg g−1) amounts of S-ZVI/PBC700. Besides, S-ZVI/PBC exhibited greater electrochemical reactivity and surface area than S-ZVI harbored by BC from dairy manure and rice straw. Additionally, Pearson correlation analysis revealed that Cr(VI) removal was significantly positively correlated to surface area (R2 = 0.90) and negatively correlated to Tafel corrosive potential (R2 = 0.88). Both desorption experiment and XPS spectra of spent sorbents showed that reduction predominated the detoxifying mechanism of Cr(VI) followed by adsorption (due to corrosively-generated iron oxides and BC) and precipitation (Cr2S3). This suggested that biochar with greater specific surface area and electrical conductivity is more favorable to immobilize S-ZVI with respect to Cr(VI) removal.

Preparation of core-shell MOF-5/Bi2WO6 composite for the enhanced photocatalytic degradation of pollutants

In this study, Bi2WO6 was used as carrier and the core-shell MOF-5/Bi2WO6 (MOF-5/BWO) photocatalyst was prepared successfully by a two-step hydrothermal method for the first time. The easily hydrolyzed MOF-5 was compounded with flower-like Bi2WO6, and the hydrolyzed sheet-like MOF-5 was evenly wrapped on the surface of flower-like Bi2WO6. A type-Ⅰheterojunction photocatalytic reaction mechanism was proposed, ·O2− and h+ were the main active substances in the photocatalysis process. Compare with Bi2WO6, 9% MOF-5/BWO has the best degradation activity, and the photocatalytic degradation of RhB can reach 99.31% in 30 ​min, which is 2.16 times than pure Bi2WO6. It can be proved by XPS that the enhanced visible light performance of the composite is due to the photogenerated electrons and holes of MOF-5 flow to the conduction band and valence band of the flower-shaped Bi2WO6, reducing the recombination rate of photogenerated electron-hole pairs. Compared with the flower-shaped Bi2WO6, the specific surface area of composite was also improved, increasing the contact between the active sites and the dye molecules on the Bi2WO6 nanosheets. In addition, the cycle experiment shows that composite material has excellent stability.

Facile preparation and characterization of anatase TiO2/nanocellulose composite for photocatalytic degradation of methyl orange

Anatase TiO2/nanocellulose composite was prepared for the first time via a one-step method at a relatively low temperature by using cellulose nanofibers as carrier and tetrabutyl titanate as titanium precursor. The morphology, structure and element composition of the composite were characterized by SEM, EDS, TEM, XRD, XPS and UV–vis DRS. The specific surface area and thermal stability of the composite were investigated by N2 adsorption–desorption and thermogravimetric analysis, respectively, and the band gaps of the prepared photocatalysts were calculated based on the UV–vis DRS results. In addition, the prepared composite was used for the photocatalytic degradation of methyl orange (aqueous solution, 40 mg L−1). It was found that the composite had a good morphology and anatase crystal structure, and Ti-O-C bond was formed between TiO2 and nanocellulose. The specific surface area of composite was increased and the thermal stability was decreased compared with the cellulose nanofiber. Moreover, the degradation rate of methyl orange was achieved as 99.72% within 30 min, and no obvious activity loss was observed after five cycles. This work might give some insights into the design of efficient photocatalysts for the treatment of organic dye wastewater.

Graphene oxide-iron modified clinoptilolite based composites for adsorption of arsenate and optimization using response surface methodology

In this study, graphene oxide and composites of graphene oxide-iron modified clinoptilolite were synthesized and used for arsenate removal from aqueous solution. All adsorbents were characterized using X-ray diffraction and specific surface area analysis. The specific surface areas of composites were found to be less than the iron modified clinoptilolite. The time required to reach equilibrium was determined as 3 hours for all adsorbents. The Box-Behnken statistical experiment design method was used to determine the effects of initial arsenate concentration, pH and the amount of adsorbent on the percent arsenate removal. Graphene oxide was not as effective as composites for arsenate adsorption from water. Arsenate adsorption on composites was showed good compatibility with the Freundlich isotherm. The maximum arsenate uptake was realized at pH 4 for graphene oxide and at pH 7 for composites. The maximum adsorption capacities obtained at the optimum points determined by using the Box-Behnken design method were calculated as 39.49, 117.98 and 124.64 µg.g−1 for graphene oxide and composites, respectively.

The synergistic effect of fullerene and 3D ordered macroporous structure on promoting photocatalytic performance

Enhancing light absorption, accelerating carrier separation and enlarging specific surface areas are effective means to promote photocatalytic performance. Herein, we utilized the synergistic effect of C60 and three-dimensional ordered macroporous (3DOM) structure on light absorption enhancement, electron transfer acceleration and reactive sites increasement to enhance photocatalytic performance of TiO2. The results show that 3DOM structure can enhance the catalytic performance by enlarging specific surface areas of composites. C60 can effectively enhance light absorption and suppress the recombination of electron-hole pairs of TiO2. The degradation mechanisms of organic pollutant by prepared composites were also systematically investigated.

Adsorption and photocatalytic degradation performances of TiO2/diatomite composite for volatile organic compounds: Effects of key parameters

The TiO2/diatomite composites with excellent adsorption and photo-degradation performances were leveraged to investigate the influences of calcination temperature and operating factors on their properties. The results showed that the calcination temperature was closely bound up with the crystallization of TiO2 and the specific surface area of composite. The composite with calcination temperature of 550 °C exhibited enhanced photocatalytic owing to the high surface area and small TiO2 crystallite size. A series of dynamic degradation experiments were conducted to investigate the effect of various operating parameters on acetone and p-xylene adsorption/degradation performances of the composite. The results illustrated that when the relative humidity (0–70%), gas flow rate (1–4 L/min), and VOC concentration (10–40 ppm) were set as the low values, the high total organic carbon degradation rate could be acquired. The total organic carbon degradation rate reached to a high value when the composite dosage was 3.76 mg/cm2. With the increase of light intensity (0.48–1.33 mW/cm2), the total organic carbon degradation rate presented an upward trend and then kept stable. The absorbent-photocatalyst hybrid TiO2/diatomite composite could be the promising VOC purification materials.

In Ukrainian

The effect of the surface modification of fumed silica (SiO 2 ) with poly(dimethylsiloxane) (PDMS) on the rheological properties of its suspensions in vaseline oil has been studied in the current work. The composites with different polymer content (from 5 to 40 wt. %) were synthesized by using the method of liquid phase adsorption modification of silica with linear PDMS-1000 (molecular weight W m ≈ 7960, degree of polymerization d p = 105). It is shown that the structural and morphological characteristics of SiO 2 /PDMS composites are significantly different from those for the initial silica, and depend on the concentration of PDMS. In particular, the specific surface area of the composites, determined by the method of low-temperature desorption of argon, is inversely correlated with the content of polymer. The morphology of SiO 2 /PDMS composites and aggregation of primary particles of fumed silica strongly depends on the method of liquid phase adsorption modification: the initial fumed SiO 2 has a wider distribution of aggregates in size than that in polymer composites according to AFM data. Suspensions with a solid phase concentration (SiO 2 /PDMS) of 5 wt. % in a lyophilic dispersion medium (vaseline oil) demonstrate typical thixotropic behavior with a characteristic hysteresis loop on the rheogram, corresponding to increasing the destruction of the dispersion structure while stepwise shear rate increment and partial its restoration while subsequent stepwise shear rate decrement. Both the effective viscosity values corresponding to the maximum destruction of the suspension structure obtained at high shear rates and the effective viscosity values corresponding to partial restoration of the structure in the subsequent stepwise shear rate decrement mode decrease with increasing polymer content in the studied composites. However, it has been found that the initial values of the effective viscosity for the studied dispersions with a practically almost intact structure (at the lowest shear rates) are higher for dispersions of SiO 2 /PDMS composites with a low concentration of PDMS 10–20 wt. % compared with similar suspensions of the initial silica. A correlation between the effective viscosity and the specific surface area of composites is shown.

Preparation and characterization of a novel ZIF-8 membrane over high voidage paper-like stainless steel fibers

A new method was employed to synthesize a novel high voidage ZIF-8 membrane over paper-like stainless steel fibers (PSSF). Firstly, paper-like stainless steel fibers (PSSF) were prepared by wet lay-up papermaking and sintering process, then the ZIF-8 membrane was coated on the PSSF support by secondary growth process. The effects of the seed layer growth time, the Hmim (2-methylimidazole)/Zn (Zinc nitrate hexahydrate) molar ratios, the solvothermal synthesis temperature and time on properties of ZIF-8 membrane/PSSF composites were investigated by modern characterization methods. The experimental results indicated that the void volume of ZIF-8 membrane/PSSF composites reached 89%. The optimal specific surface area of composites was 398 m2/g and the total pore volume was 0.174 cm3/g. Specifically, the size of seeds were approximately 250 nm when Hmim/Zn molar ratios and seed layer deposition time were 80 and 12 h, respectively. Under the condition of optimal seed layer, ZIF-8 membrane/PSSF composites showed outstanding continuity, compactness, free-defect and crystal shape when solvothermal synthesis time and solvothermal synthesis temperature were 24 h and 100 °C, respectively.

Cu2O and rGO Hybridizing for Enhancement of Low-Concentration NO2 Sensing at Room Temperature

The spherelike Cu2O and the hybrids with reduced graphene oxide (rGO) have been synthesized successfully by a facile solution-based self-assembly method. The structure, morphology, composition, and specific surface area of composite were characterized by XRD, SEM, FTIR, XPS, and BET analysis, respectively. The gas-sensing properties to 1 ppm of NO2 at room temperature were also examined. The results indicated that the 1 wt % rGO/Cu2O composite not only exhibits 2.8 times higher response than that of pristine Cu2O and excellent selectivity but also owns rapid response and recovery at room temperature, indicating the composite is a promising sensing material for room temperature detection of low-concentration NO2. The enhanced sensing properties were discussed in detail, which can mainly be attributed to increased gas adsorption active sites and the fast carriers transport due to the incorporating of rGO.

In situ fabrication of SnO2/S-doped g-C3N4 nanocomposites and improved visible light driven photodegradation of methylene blue

Herein, several Sn/CNS composite photocatalysts consisted of SnO2 and sulfur-doped graphitic carbon nitride (CNS) were in situ fabricated through thermal condensation of thiourea and tin(IV) chloride as starting materials. The synthesized Sn/CNS photocatalysts with different SnO2 contents (1.6, 7.7 and 8.5wt%) were characterized by several techniques. The phase structures and morphology results of composite indicated that the perfect crystalline structure and the stacking degree of CNS phase were disrupted during the formation of SnO2 particles, so that specific surface area of composite was enhanced about 2.8 times compared with that of pure CNS photocatalyst. The optimized photocatalyst, i.e. SnO2(7.7)/CNS composite, showed the highest photocatalytic efficiency for degrading methylene blue (MB) under visible light irradiation among the individual CNS and SnO2 photocatalysts. The improved photoactivity could be related to introducing S dopant in CNS backbone which led to increasing the visible light absorption. Besides, due to loading the SnO2 nanoparticles, heterojunctions were formed between SnO2 and CNS which facilitated the effective charge transfer through interfacial interactions between both components. The heterojunction prepared by the in situ strategy illustrated excellent stability for the photocatalytic activity under optimized conditions obtained by response surface methodology (RSM) method. It may be attributed to the strong surface interaction between individual components during evolution of CNS structure. It was also found that •O2− was the main reactive species in the degradation reaction and a possible mechanism for the enhanced photocatalytic activity of the SnO2(7.7)/CNS composite was discussed in detail.

Photocatalytic Degradation of Gaseous Formaldehyde by Polyvinyl Chloride Gauze Immobilized TiO2/Tourmaline Composites

TiO2 was prepared by a sol-gel method and composited with tourmaline to improve the photocatalytic activity utilizing the spontaneous electric field of mineral. Then, the TiO2/tourmaline composites were supported onto Polyvinyl chloride (PVC) gauze to provide a convenient application for degradation of indoor formadehyde (HCHO) gas. The composites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), automatic surface area and porosity analyzer (BET). The results showed that the grain size of TiO2 decreased after compositing with tourmaline, and the specific surface area of composites is much higher than that of the pure TiO2. The TiO2/tourmaline gauze exhibited excellent photocatalytic activity for the degradation of HCHO (100mg/m3), which was 5 times higher than that of TiO2 gauze. Moreover, the photocatalytic activity of the composite gauze was fully maintained after four photocatalytic cycles. The enhancement of photocatalytic activity was mainly due to the improvement of catalyst surface performances and capture of photoelectrons by electric field of tourmaline.

Hybridization of ZnSnO3 and rGO for improvement of formaldehyde sensing properties

The rGO/ZnSnO3 composites have been elaborately synthesized by a facile solution-based self-assembly synthesis method at low temperature. The structure, morphology, thermal stability, composition and specific surface area of composite were characterized by XRD, SEM, TG, XPS and BET analysis, respectively. The sensing experiments show that the sensor based on 3wt% rGO composite not only exhibits high sensitivity (low limit of detection), excellent selectivity and linearity relationship between responses and formaldehyde concentration from 1 to 10ppm, but also exhibits fast response and recovery at operating temperature of 103°C. The enhanced sensing mechanism of the hybrid to formaldehyde was discussed in detail, which can mainly be ascribed to the large specific surface area for gas adsorption, porous channels for gas diffusion, the fast carrier transport benefited from rGO and the formation of heterojunction at the interface between the rGO and ZnSnO3.

Hydrogen uptake of cobalt and copper oxide-multiwalled carbon nanotube composites

Hydrogen storage capacity of a pristine multi-walled carbon nanotubes is increased 10-fold at 298 K and an equilibrium hydrogen pressure of ∼23 atm, upon addition of a hydrogen spillover catalyst cobalt- and copper oxide, from 0.09 to 0.9 wt.%. In situ reduction method is utilized to synthesize Co-oxide/MWCNTs and Cu-oxide/MWCNTs composite. Blocking of channels and pores of MWCNTs by oxide nanoparticles during preparation method is responsible for low BET specific surface area of composites compared to pristine sample. X-ray diffraction, scanning, and transmission electron microscopy demonstrates nanostructural characterization of MWCNTs and composites. Thermogravimetric analysis of two oxide/MWCNTs composites showed a single monotonous fall related to MWCNTs gasification. Enhancement of hydrogen storage of both composites is attributed to the spillover mechanism due to decoration of Co and Cu-oxide nanoparticles on the outer surface of MWCNTs.

Preparation and characterization of a novel gradient porous ZSM-5 zeolite membrane/PSSF composite and its application for toluene adsorption

A novel gradient porous ZSM-5 membrane/PSSF composite was prepared by the wet lay-up papermaking process and secondary growth process. Firstly, the paper-like sintered stainless steel fibers (PSSFs) support was prepared by the wet lay-up papermaking process and sintering process, then a ZSM-5 membrane was fabricated on this PSSF support by secondary growth process. The morphology and structure of ZSM-5 membrane/PSSF composite were characterized by SEM, XRD and ASAP 2020, respectively. The experimental results indicated that the junctures of stainless steel fibers were completely sintered together to form a three-dimensional network structure and ZSM-5 membrane was fabricated on the PSSF support. The specific surface area of composite was 145.1m2/g, which was calculated with the BET (Brunauer–Emmett–Teller) method, and the total pore volume was 0.1547cm3/g. The adsorption breakthrough curve of toluene in the structured fixed bed filled with both granular activated carbons (GACs) of 2.4cm in the inlet of bed and NaZSM-5/PSSF composites of 0.6cm in the outlet of bed was also investigated, comparing with that in individual GAC fixed bed with bed height of 3cm. The length of unused bed was calculated according to the breakthrough curve data. The experimental results showed that the length of unused bed in structured fixed bed was obviously decreased.