Carbon-based Aerogel Research Articles

Highly stable binder free CNTs/rGO aerogel electrode for decolouration of methylene blue & palm oil mill effluent via electro-Fenton oxidation process.

In this study, single wall carbon nanotubes (CNTs)/reduced graphene oxides (rGO) aerogels were prepared by a one-pot hydrothermal process without using a binder. The produced CNTs/rGO aerogel was used as cathode in electro-Fenton system for the decolouration of methylene blue (MB) and palm oil mill effluent (POME). The addition of CNTs increased the surface area, pore volume and conductivity of the rGO aerogel, which further enhanced their performance as cathode towards the decolouration of MB and POME via electro-Fenton reaction. Complete decolouration of MB using rGO aerogel without CNTs could not be achieved. The effect of electro-Fenton reaction parameters conducted using the aerogel samples including, current, electrolyte concentrations and pH, were investigated accordingly. The CNTs/rGO aerogel electrode also showed high stability and reusability for up to six consecutive treatment cycles for MB. Besides, the CNTs/rGO aerogel also showed good performance in treating POME with 69.8%, 47.6% and 58.1% of reduction in true colour, total organic carbon (TOC) and chemical oxygen demand (COD), respectively, via 60 minutes electro-Fenton reaction. This study showed that CNTs/rGO aerogels with high porosity and stability can be prepared using simple procedure without adding binder. This fully carbon-based aerogel can serve as effective cathode for decolouration of organic dye and effluent.

Construction of a Carbon Nanomaterial-Based Nanocomposite Aerogel for the Removal of Organic Compounds from Water

Overutilization of organic-based compounds (e.g., fertilizers) in agricultural settings continues to cause concern due to potential adverse impacts on the health of humans and the environment. Adsorbents, such as activated carbon, are widely used due to their ability to adsorb various contaminants. Limitations in the effectiveness of activated carbon, where high uptake capacities are desired, require the need for alternatives to current state-of-the-art adsorbents. In this work, the adsorption capability of a lightweight, carbon-based aerogel is presented. The aerogel is composed of 0 to 2 wt % mixture of both graphene nanoplatelets (GnP) and single-walled carbon nanotubes (SWCNT). Two organic compounds, 2,4-dichlorophenoxyacetic acid (2,4-D) and 1-pyrenebutyric acid (PBA), served as the contaminants of interest. Results show that the aerogel containing 0.2 wt % SWCNT-GnP achieved an uptake capacity of 0.22 mg of 2,4-D/mg of aerogel and 0.083 mg of PBA/mg of aerogel. Compared to activated carbon, from a k...

High Performance Lithium–Sulfur Batteries with a Sustainable and Environmentally Friendly Carbon Aerogel Modified Separator

Carbon-based aerogel prepared via direct conversion of natural biomass has wide application prospects in the environment and energy field. Herein, the sustainable and environmentally friendly porous carbon aerogel is prepared through hydrothermal treatment, freeze-drying, and postpyrolysis using sweet potato as the precursor. The as-prepared carbon aerogel is used to modify the commercial separator of lithium–sulfur batteries to solve the problems of poor cycle life and low utilization rate of active substances. The carbon aerogel coating can not only suppress the shuttle effect of the polysulfide intermediates during cycling and reduce the cell resistance but also act as an upper current collector to increase the utilization rate of sulfur. The cell with carbon aerogel modified separator exhibits high electrochemical performance. The results show that the initial discharge capacity is 1216 mAh/g at 0.1 C and the reversible discharge capacity retains 431 mAh/g after 1000 cycles at 1 C with the Coulombic e...

3D carbon aerogel-supported PtNi intermetallic nanoparticles with high metal loading as a durable oxygen reduction electrocatalyst

Highly active and cost-effective oxygen reduction reaction (ORR) catalysts that have high metal loading and enhanced durability are desirable for the practical application in direct methanol fuel cells. Here, the preparation of a three dimensional (3D) carbon-based aerogel (CA) composed of graphene and multi-walled carbon nanotubes is reported and used as a support for an ordered PtNi intermetallic catalyst (OPtNi/CA) with a metal loading of 80 wt%. X-ray diffraction and transmission electron microscopic measurements confirm the formation of highly dispersed ordered PtNi intermetallic nanoparticles with a mean particle size of ca. 15.0 ± 1.0 nm. The as-prepared catalyst exhibits enhanced activity and durability for the ORR when compared to the Pt/C catalyst from BASF. The mass and specific activities of the ORR at 0.90 V on OPtNi/CA is ca. 1.4 and 1.8 times higher, respectively, than that using the commercial Pt/C catalyst. After an accelerated stress test, the mean particle size of the OPtNi/CA catalyst nearly kept unchanged. Both the improved activity and durability of the OPtNi/CA catalyst could be ascribed to the formation of an intermetallic compound, the uniform dispersion of PtNi nanoparticles, and the 3 D structure of the support.

Aligned α-FeOOH nanorods anchored on a graphene oxide-carbon nanotubes aerogel can serve as an effective Fenton-like oxidation catalyst

The self-assembled synthesis of a hierarchical graphene oxide (GO)-carbon nanotubes (CNTs)-α-FeOOH decorated composite aerogel (α-FeOOH@GCA) through a facile in-situ hydrolysis route is reported for the first time and the materials was tested for its performance as Fenton-like catalyst. The introduction of GO-CNTs clearly mediated the morphology to aligned α-FeOOH nanorods (ca. 100nm) within aerogel matrix comparing with pristine urchin-like α-FeOOH three-dimensional microstructures (ca. 1μm). This three dimensional porous aerogel network provided efficient charge/mass-transfer leading to great enhancement of the catalytic activity of α-FeOOH. The outstanding catalytic performance of this composite in degradation of organics with different charge and structure, i.e. Orange II (OII), rhodamine B (RhB), methylene blue (MB), phenol and endocrine disruptor bisphenol A (BPA) was demonstrated. For example, the discoloration of OII with pseudo first-order rate constant of 0.10min−1 significantly exceeded that of pristine α-FeOOH. At relatively low concentration of α-FeOOH@GCA catalyst (125mgL−1) and H2O2 (0.55mM) showed excellent catalytic activity for efficient (∼99%) discoloration of OII (40mgL−1) under a 60min UV365 irradiation in the pH range 3–10. The different charge of five target contaminats greatly determined the surface-catalyzed degradation kinetics at natural solution pH in the order of cationic>neutral>anionic organics due to the negatively charged carbon-based aerogel matrix. The new identified desulfonation intermediates elucidated through UPLC–MS analysis indicated two reaction pathways: 1) hydroxylation and 2) desulfonation by-products followed by cleavage of the azo bond as the predominant degradation pathway of OII. The elimination of the acute toxicity of the parent contaminant to luminescent bacterium Q67 was consistent with the formation of less toxic degradation by-products identified. Free radical quenching studies accessed the role of hydroxyl radical (OH), superoxide anion radical (O2−) and singlet oxygen (1O2) as the dominating reactive oxygen species (ROS). The quantitative studies to measure radical concentrations using relative molecular probes showed the effective activation of H2O2 led to high rate production of ROS accounted for OII degradation. The greatly enhanced photocatalytic property of this hybrid was correlated with the efficient conversion between Fe2+/Fe3+ and synergistic coupling between α-FeOOH and carbon-based aerogel matrix evidenced through the formation of FeOC chemical bonds was verified by X-ray photoelectron (XPS) analysis. Based on its simple and scalable preparation route as well as its excellent UV365 or visible light-responsive catalytic performance, this hybrid exhibits a high potential to be used as an efficient and environmental-friendly catalyst for water remediation.

Nanocellulose-assisted low-temperature synthesis and supercapacitor performance of reduced graphene oxide aerogels

Abstract Here, we have synthesized reduced graphene oxide (rGO) aerogels using a nanocellulose-assisted low temperature (less than 500 °C) thermal treatment route where nanocelluloses promote the gelation of graphene oxide (GO) solution that benefits the fabrication of GO aerogels from low concentration dispersion (2.85 mg mL−1), and after their thermal decomposition the residual nanofibers act as spacer both prevent the re-stacking of graphene sheets and integrate with rGO sheets to give a particular kind of carbon-based aerogel along with numerous defects (holes). Thermal decomposition of nanocellulose appears to be complete beyond 350 °C thus its presence in form of amorphous carbon nanofibers in rGO sheets. The rGO aerogels synthesized at 350 °C provide the best balance in terms of wide interlayer spacing, high content of CO-type functional groups, and high defects content. This translates into a high discharge capacitance of 270 F g−1 at a current rate of 1 A g−1 for compressed rGO aerogels without any binder or conductive additive. Detailed electrochemical tests using 6 M KOH electrolyte establish the fact that pseudocapacitance component has substantial contribution towards the overall capacitance; closely approaching the contribution of the double layer capacitance that is the most dominant capacitance component.

Green and facile fabrication of carbon aerogels from cellulose-based waste newspaper for solving organic pollution

Carbon-based aerogel fabricated from waste biomass is a potential absorbent material for solving organic pollution. Herein, the lightweight, hydrophobic and porous carbon aerogels (CAs) have been synthesized through freezing–drying and post-pyrolysis by using waste newspaper as the only raw materials. The as-prepared CAs exhibited a low density of 18.5mgcm−3 and excellent hydrophobicity with a water contact angle of 132° and selective absorption for organic reagents. The absorption capacity of CA for organic compounds can be 29–51 times its own weight. Moreover, three methods (e.g., squeezing, combustion, and distillation) can be employed to recycle CA and harvest organic pollutants. Combined with waste biomass as raw materials, green and facile fabrication process, excellent hydrophobicity and oleophilicity, CA used as an absorbent material has great potential in application of organic pollutant solvents absorption and environmental protection.

Wetting angle and surface tension of germanium melts on different substrate materials

The sessile drop technique has been used to measure the wetting angle and the surface tension of molten germanium (Ge) on various substrate materials. Sapphire, fused silica, glassy carbon, graphite, SiC, carbon-based aerogel, pyrolytic boron nitride (pBN), AlN, Si 3N 4, and CVD diamond were used as substrate materials. In addition, the effects of different cleaning procedures and surface treatments on the wetting behavior were investigated. The highest wetting angles with values around 170° were found for pBN substrates under active vacuum or with a slight overpressure of 5 N argon or forming gas (2% hydrogen in 5 N argon). The measurement of the surface tension and its temperature dependence for Ge under a forming gas atmosphere resulted in γ( T)=591−0.08 ( T− T m)[10 −3N/m].