Super High Specific Surface Area Research Articles

Review on Thermal Conductivity of the Graphene Reinforced Resin Matrix Composites

Graphene is a two-dimensional nanostructure filler with high thermal conductivity (5000 W/mK) and excellent mechanical properties, which has a very wide application prospect. Graphene is with super high specific surface area, which provides a greater contact area with polymer matrix. Then it is more easy to form the thermal conductive heat channels, which could improve the thermal conductivity of composite materials. The concentration, the ratio of geometrical diameters, the dispersion in the matrix and the interfacial bonding between graphene and the matrix materials will greatly affect the thermal conductivity of graphene reinforced composites. However, the graphene nanosheets can be easy to stack together and difficult to be dispersed into the solvent and polymer matrix. In order to improve the interfacial combination between graphene nanosheets and the matrix so as to reduce the interfacial thermal resistance of the composites, it is usually to modify the surface of graphene nanosheets, which mainly includes non-covalent modification and covalent modification. In this paper, researches on the thermal conductivity of graphene were reviewed, and the existing problems and the future research focus were also discussed.

Meso-/microporous carbon as an adsorbent for enhanced performance in solid-phase microextraction of chlorobenzenes

There is urgent demand for the design of advanced coating materials for solid-phase microextraction (SPME) for water quality monitoring and assessment because of the global occurrence of chlorobenzenes (CBs). In this study, we proposed a dual-order activation method in which potassium hydroxide is used to modify pre-activated calcium citrate to synthesize a highly developed meso-/microporous carbon (MMC). The as-obtained MMC presented well-developed porosity with a super-high specific surface area (2638.09 m2 g−1), abundant meso-/micropores (0.5–10 nm), high hydrophobicity, excellent thermal stability (>720 °C), and a partly graphitized structure. As a coating material for headspace-SPME, the MMC-coated fiber exhibited outstanding extraction capability for CBs (up to 48.5 times higher than that of commercial fibers), which may be attributed to multiple interactions between the MMC and the pollutants, including size selectivity, micropore filling, π-π stacking and hydrophobicity. Finally, a satisfactory method using an MMC-coated fiber coupled with gas chromatography and electron capture detection was developed with good linearity (1–1000 ng L−1, R2 > 0.9982), high enrichment efficiencies (enrichment factors, 861–7819), low limits of detection (0.003–0.072 ng L−1), excellent repeatability (0.7–5.3%) and reproducibility (1.7–5.1%), and outstanding recoveries (90.18–103.02%) when applied to determine trace CBs in real water samples. These results suggest that MMC is a promising coating material for the SPME of CBs.

Electrosynthesized nanostructured polypyrrole on selective laser melted titanium scaffold

In this work, nanofiber polypyrrole (PPy) was electropolymerized on the three dimensional surface of SLM-Ti scaffold. The in situ measurement reveals that the potential variation within the 6.2 mm thickness porous SLM-Ti sample is about 20 mV resulting from the conducting property of PPy. SEM characterization shows that the diameter and thickness of PPy nanofiber fabricated at inner depth is smaller and thinner than that at the outer surface due to the lower effective overpotential and current inside porous SLM-Ti electrode. Based on the comparative electrochemical measurements, it is found that the nucleation and growth rate of PPy polymerization on 3D SLM-Ti electrode is slower than that of PPy on 2D SLM-Ti electrode. Although the nanofiber PPy film synthesized on porous scaffolds exhibits a relatively poorer reversibility and long-terms stability than that on dense sheets, there is a great potentiality to increase the electrochemical activity due to its super-high specific surface area. The work provides the fundamental perspective to study the mechanism of PPy electropolymerization on 3D SLM-Ti scaffold.

Influence of sulfonated GO/sulfonated biopolymer as polymer electrolyte membrane for fuel cell application

Graphene oxide is well known as a advanced functional material because of its super high specific surface area, as well as excellent amphipathicity. Sulfonated graphene oxide bio nanocomposite membranes are presented as a potential proton exchange membrane for fuel cell applications. The GO nanopowder was produced from graphite powder by the modified Hummer’s method and then sulfonated by chlorosulfonic acid as a sulfonic reagent. The s-GO-based s-CS/PEO composite membranes were prepared by solution casting technique. The synthesized electrolytes are studied by different characterization to check the electrical and thermal properties of the membrane. FTIR and Raman showed the formation of GO, s-GO and prepared electrolytes interaction between the functional groups respectively. The maximum ionic conductivity of s-Chitosan (s-CS)/PEO/s-GO nanocomposite membranes at 6 wt% of s-GO in the order of 10−2 S/cm. Moreover, the existence of the intermolecular interactions between sulfonated-CS/PEO and s-GO can improve the thermal stability and interfacial compatibility between nanofiller and polymer matrixes.

Activated carbon derived from harmful aquatic plant for high stable supercapacitors

Considering cost and environmental protection, the harmful aquatic plant altemanthera philoxeroides derived carbon material with super high specific surface area (2895 m2 g−1) is an ideal electrode material for supercapacitor. The structure and composition of these carbon materials were characterized by SEM, EDS, XPS and BET measurements. The obtained material exhibits a maximum specific capacitance of 275 F g−1 at 0.5 A g−1 and retains a capacitance of 210 F g−1 even at 50 A g−1. In addition, it also shows excellent capacity retention of 5000 cycles at 10 A g−1.

Synthesis of Bamboo-Based Activated Carbons with Super-High Specific Surface Area for Hydrogen Storage

Activated carbons (ACs) were developed from the agricultural by-products of moso bamboo by pyrolysis carbonization and the KOH activation process. N2 adsorption-desorption at 77 K, thermogravimetric analysis (TG), X-ray photoelectron spectrometry (XPS), element analysis (EA), X-ray diffraction (XRD), scanning electron microscopy (SEM), high- resolution transmission electron microscopy (HRTEM), and Fourier transform infrared spectroscopy (FTIR) were used to investigate the synthesis process, the impact of the weight ratio of KOH/bamboo charcoal (BC), and the characteristics of the bamboo charcoal and ACs produced. The results showed that the developed bamboo ACs achieved surface areas (SBET) as high as 3208 m2/g and micropores volumes (VDR) as high as 1.01 cm3/g. The carbonation and activation of the bamboo resulted in the enhancement of the microstructure of the bamboo ACs, and hence improvements in the sorption behavior and storage capacity. The highest hydrogen storage capacities achieved were 6.6 wt.% at 4 MPa and 2.74 wt.% at 1 bar, both at 77 K, which were much higher than those of a well-known commercial activated carbon.

Ultra-low-density GNS/CA composite aerogels with ultra-high specific surface for dye removal

Ultra-low-density graphene nanosheet (GNS)/carbon composite aerogels (CAs) were prepared via GO (graphene oxide)/RF (resorcinol–formaldehyde) aerogel composite, supercritical fluid drying, and carbonization. Graphene oxide was found to act as an efficient anti-shrinkage additive in the carbonization process, making the linear shrinkage ratios decrease from 78 % to only 10 % (25 % GO content). The density of the aerogels thus decreases from 115 to 24.4 mg cm−3. 25 % GO-composited aerogel exhibits over two times modulus increase and over 11 times specific modulus increase in comparison with pure carbon aerogel. The microstructure results show that GO is fully cross-linked with RF polymers, makes the reaction more sufficient and ultimately strengthens the nanostructure to withstand the damage of carbonization. The resultant composite carbon aerogels exhibited super high specific surface area (as high as 2899 m2 g−1), good mechanical property, and high adsorption capacity of 403 mg g−1 for methylene blue.

Thorny TiO2 nanofibers: Synthesis, enhanced photocatalytic activity and supercapacitance

TiO2 nanofibers with special thorny morphology were successfully synthesized by the combination of electrospinning and silica etching technique. This elaborate TiO2 nanostructures exhibited super-high specific surface area (329.7 m2 g−1), which was nearly 13 times higher than that of primary electrospun TiO2 nanofibers (25.6 m2 g−1). The morphological, component, structural and optical properties were characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectrum (EDS), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectra (XPS) and UV–visible (UV–vis) diffused reflectance spectroscopy (DRS). Compared with the pristine electrospun TiO2 and SiO2/TiO2 nanofibers, the thorny TiO2 nanofibers not only possessed improved photocatalytic efficiency in photodegradation of Rhodamine B (RhB), but also showed higher specific capacitance in the supercapacitor applications. These results suggest that the thorny TiO2 nanofibers with super large specific surface area exhibit potential applications in both photocatalysis and supercapacitor fields.

Normal-pressure microwave rapid synthesis of hierarchical SnO2@rGO nanostructures with superhigh surface areas as high-quality gas-sensing and electrochemical active materials

Hierarchical SnO2@rGO nanostructures with superhigh surface areas are synthesized via a simple redox reaction between Sn(2+) ions and graphene oxide (GO) nanosheets under microwave irradiation. XRD, SEM, TEM, XPS, TG-DTA and N2 adsorption-desorption are used to characterize the compositions and microstructures of the SnO2@rGO samples obtained. The SnO2@rGO nanostructures are used as gas-sensing and electroactive materials to evaluate their property-microstructure relationship. The results show that SnO2 nanoparticles (NPs) with particle sizes of 3-5 nm are uniformly anchored on the surfaces of reduced graphene oxide (rGO) nanosheets through a heteronucleation and growth process. The as-obtained SnO2@rGO sample with a hierarchically sesame cake-like microstructure and a superhigh specific surface area of 2110.9 m(2) g(-1) consists of 92 mass% SnO2 NPs and ∼8 mass% rGO nanosheets. The sensitivity of the SnO2@rGO sensor upon exposure to 10 ppm H2S is up to 78 at the optimal operating temperature of 100 °C, and its response time is as short as 7 s. Compared with SnO2 nanocrystals (5-10 nm), the hierarchical SnO2@rGO nanostructures have enhanced gas-sensing behaviors (i.e., high sensitivity, rapid response and good selectivity). The SnO2@rGO nanostructures also show excellent electroactivity in detecting sunset yellow (SY) in 0.1 M phosphate buffer solution (pH = 2.0). The enhancement in gas-sensing and electroactive performance is mainly attributed to the unique hierarchical microstructure, high surface areas and the synergistic effect of SnO2 NPs and rGO nanosheets.

Highly-Ordered Mesoporous Carbon Nitride with Ultrahigh Surface Area and Pore Volume as a Superior Dehydrogenation Catalyst

In this work, a highly ordered mesoporous carbon nitride nanorods with 971–1124 m2 g–1 of superhigh specific surface area, 1.31–1.79 cm3 g–1 of ultralarge pore volume, bimodal mesostructure, and 9.3–23 wt % of high N content was prepared via a facile nanocasting approach using SBA-15 as template and hexamethylenetetramine as carbon nitride precursor, and the specific surface area and pore volume as well as N content are strongly dependent on the chosen precursor and pyrolysis temperature. The as-prepared materials were well characterized by HRTEM, FESEM, XRD, BET, Raman, FT-IR, XPS, and the textural structure and morphology were confirmed. The finding breaks through the bottleneck problems for fabricating mesoporous carbon nitride with both ultrahigh surface area and super large pore volume by employing an unexplored hexamethylenetetramine as carbon nitride precursor. The current synthetic strategy can be extended to the preparation of various mesoporous carbon nitride with different textural characterist...

Influence of structure of activated carbon with superhigh specific surface area on hydrogen storage capacity

Abstract

Some Factors Determining the Volume Resistivity of Filled Natural-Rubber-Based Nanocomposites

In recent years, special grades of electroconductive carbon black have been developed to overcome the usage of large amounts of filler in the preparation of composites with desired electrical properties. Characteristic features of the novel carbon black are its superhigh specific surface area and structure, which are many times higher than those of conventional electroconductive carbon black. The present article reports on natural-rubber-based composites, filled with carbon black of superhigh specific surface area and structure. New results concerning the influence of change in the filler concentration, applied pressure, and temperature on the volume resisitivity of the composites are presented and discussed. It has been found that the new filler lowers the percolation threshold greatly and ensures very high electroconductivity at low content. The influence of applied pressure on the volume resistivity depends on whether the amount of filler used is sufficient to reach or pass the percolation threshold: when the percolation threshold is not reached, the volume resistivity increases with increasing pressure; after reaching the percolation threshold, the volume resistivity decreases with increasing pressure. With increase in temperature, the volume resistivity of the examined composites decreases. With increase in the degree of filling, the examined hysteresis decreases too. The results obtained for the new conductive rubber composites may be considered as a novel contribution in the field of polymer materials research.

Synthesis of Carbon/Carbon Core/Shell Nanotubes with a High Specific Surface Area

Novel carbon/carbon core/shell nanotubes (C/C-NTs) composed of well-crystallized core carbon nanotubes (CNTs) and structurally disordered carbon shells were prepared for obtaining a new type of nanotube material with high specific surface area (SSA). The disordered carbon shells were prepared by coating polyaniline, (PANI) layers on the core CNTs through in situ polymerization and Subsequent carbonization. Chemical activation was conducted for the C/C-NTs with KOH at 1123 K to prepare activated C/C-NTs (AC/C-NTs). Scanning electron microscopy, transmission electron microscopy (TEM), X-ray diffraction, Raman spectroscopy, and an adsorption analyzer were used to characterize the nanotube samples. The outer carbon shells thermally converted from the PANI layers are much less ordered and thus much more reactive than the CNTs. The AC/C-NTs tend to have Much higher SSA than that obtained by directly activating the CNTs, and the obtained SSA for the AC/C-NTs is as high as 2924 m(2)/g, which is the highest among the existing nanotube materials. TEM shows that the hollow structure and high crystallinity of the core CNTs were well preserved during carbonization and activation. The novel AC/C-NTs may find important applications in many areas such as supercapacitors, catalyst supports, adsorption, and hydrogen storage due to their superhigh SSA and nanotubular structure. The present work provides a way for preparing other core/shell nanotube or nanowire materials with high SSA.

Microstructural Changes during Activation Process of Isotopic Carbon Fibers using CO2 Gas(II)-XRD Study

A development of micropores of <TEX>$CO_2$</TEX>activated isotropic carbon fibers from TEM was observed. It was observed that the micropores of activated carbon fibers(ACFs) were consisted of slit-shaped pores(SP) and cylinder-shaped pores(CP). The SPs were formed between two parallel-carbon layers, and the CPs were formed at a place which is connected polygonally by more than two carbon layers. It was shown that the CPs of the ACFs were developed at high degree of burn-offs and at high activation temperature. The pore size distribution of the best ACF, which was observed at a highest value of specific surface area(3,495 <TEX>$\m^2$</TEX>/g), showed a continuous distribution in the range of about <TEX>$4∼l5\AA$</TEX>, and the median pore size was 6.7<TEX>$\AA$</TEX>. The super-high specific surface area of ACFs was found to be due to that the SPs were connected with a maximum size of 7∼8<TEX>$\AA$</TEX> continuously, It is possible that the SPs should be formed in the ACFs in order to show super-high SSA.