Carbon Aerogel Microspheres Research Articles

Synthesis of hydrophilic sulfur-doped carbon aerogel microspheres and their mechanism of efficient removal of Sb(III) from aqueous solution

Antimony pollution is well recognized to induce cancer and deformity. By polymerization technique, a carbon aerogel microsphere (Ce@SCA) modified by Ce and S with micron size, well-developed pore structure, and large specific surface area was created. Ce@SCA exhibited the advantages of efficient selectivity and high adsorption capacity for Sb(III) in water. The highest adsorption capacity derived using the Sips isothermal model was 345.18 mg∙g−1, and the Sb (III) adsorption process was thermodynamically estimated as spontaneous, exothermic, and entropy-decreasing chemisorption. Meanwhile, Ce@SCA can convert highly toxic Sb(Ⅲ) into Sb(Ⅴ), which is suitable for the remediation of antimony-contaminated water bodies. X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) were analyzed to elucidate the adsorption mechanism and to propose optimized adsorption configurations. A considerable number of –OH and -SH on the surface may increase the binding site of Sb, and the creation of S-Sb, O-Sb, and Ce-O-Sb covalent bonds was the key to Sb adsorption. This research provides a simple method for preparing cerium oxide-loaded and sulfur-doped carbon aerogel (Ce@SCA) with mild conditions and no hazardous waste, which also has superior adsorption properties for Sb (III) and high reusability.

Fabrication of high-surface-area, SiO2 supported polyimide carbon aerogel microspheres: electrochemical application

A series of polyimide (PI)/SiO2 aerogel microspheres were prepared by using polyamide acid salt and hydrolyzed tetraethyl orthosilicate based on the reverse-phase emulsion method. Then, PI/SiO2 aerogel microspheres were carbonized and etched to obtain carbon aerogel microspheres (CAMs). Scanning electron microscope, transmission electron microscope and nitrogen isothermal adsorption were used to characterize the micro-morphology and pore structure of the microspheres; and electrochemical workstation was used to test the electrochemical performance of the CAMs. The results showed that CAMs with different pore structures and specific surface area were obtained by adjusting the content of SiO2. Highest specific surface area of 1166.9 m2 g−1 and a total pore volume of 1.2369 cm3 g−1 were achieved at a SiO2 content of 50%. When used as the electrode materials for supercapacitors, these CAMs demonstrated a maximum specific capacitance of 125.1 F g−1 in a three-electrode system and a maximum capacitance of 53.3% at 30 A g−1. This article provides a new strategy for the preparation of CAMs with high specific surface area by using linear PI precursor and SiO2 support skeleton.

New method for efficient removal of Cr(VI) by recoverable magnetic nitrogen-doped carbon aerogel microspheres: Kinetics and mechanism

• The nZVI and N co-doped magnetic carbon aerogel composites were synthesized. • nZVI@NCA900 displayed high Cr(VI) removal capacity of 266.79 mg·g −1 at 318 K. • Cr(VI) can be reduced to Cr(III) by nZVI and N-containing functional groups. • Simulation results by DFT prove that N-doped show positive effect. • The nZVI@NCA could provide magnetism after several adsorption and desorption cycles. The efficient removal of hexavalent chromium from solution is a challenging task, in this paper, the nZVI and nitrogen co-doped magnetic carbon aerogel microsphere composites (nZVI@NCAs) were prepared via the microemulsion polymerization and subsequent carbonization process, and were expected to satisfactory performance in the removal of Cr(VI). From batch experiments, the Cr(VI) removal process by nZVI@NCA900 fitted better with the pseudo-second-order model. The optimal nZVI@NCA900 was superior to that of most magnetic carbon-substrate composites, displaying high Cr(VI) adsorption capacity of 266.79 mg·g −1 at 318 K. Additionally, it was found that Cr(VI) was reduced to the low-toxicity Cr(III) from the results analyzed by XPS, and nZVI@NCA900 exhibited Cr(VI) reduction performance of 33.92% Cr(VI) reduced to Cr(III). The reaction between the nZVI@NCAs and Cr(VI) was pH-dependence, endothermic and spontaneous. Removal mechanisms might involve multiple processes. The nZVI particles on the surface acted as reductants to reduce Cr(VI) to Cr(III) and form Cr(III)/Fe(III) hydroxides to precipitate on nZVI@NCAs. Simulation results by DFT prove that N is an active site and show positive effect in the adsorption system. N atoms were used as active sites to stabilize the interaction with Cr(VI) via adsorption attributed to electrostatic and act as electron donors for reduction of Cr(VI). The nZVI particles encapsulated by carbon aerogels could provide magnetic stability after acid reaction, which was beneficial to the separation of adsorbents after reaction and reuse for many cycles. These results provide a new view for developing magnetic carbon materials to remove Cr(VI) from contaminated water.

Carbon aerogel microspheres with in-situ mineralized TiO2 for efficient microwave absorption

Carbon aerogel microspheres with in-situ mineralized TiO2 for efficient microwave absorption

Ultrathin MoSe2 nanosheets decorated on carbon aerogel microspheres for high-capacity supercapacitor electrodes

A new MoSe 2 /CRF electrode was successfully constructed, which possessed enhanced specific capacitance and high cycling stability via the synergistic effect of MoSe 2 nanosheets and carbon aerogel microspheres. • MoSe 2 nanosheets and carbon aerogel microspheres hybrid via solvent-thermal method was prepared. • MoSe 2 NSs/CRF electrode exhibits an excellent specific capacitance and a high cycling stability. • Porous carbon aerogel microspheres restrict the aggregation of MoSe 2 nanosheets. • MoSe 2 NSs/CRF has potential as an electrode material in supercapacitor fields. Two-dimensional layered molybdenum selenide nanosheets have been a promising electrode material for electrochemical energy storage because of their high theoretical capacitance. However, the intrinsic low electrical conductivity and inferior structural stability impede its real application. Herein, MoSe 2 nanosheets are incorporated into carbon aerogel microspheres (MoSe 2 NSs/CRF) via a facile solvent-thermal method. The specific surface area and electric conductivity of the MoSe 2 NSs/CRF electrode were increased simultaneously because of its incorporation with porous carbon aerogel microspheres. As a result, the MoSe 2 NSs/CRF electrode exhibits an excellent specific capacitance of 498F g −1 at a current density of 1 A g −1 , which is 3 times higher than that (136F g −1 ) of the pristine MoSe 2 nanosheets. With a 5-fold increase to 5 A g −1 , it still retains 278F g -1 and high cycling stability of 127.2% of the initial retention after 2500 cycles at 100 mV s −1 . Moreover, we fabricated a symmetric supercapacitor (SC) using a composite composed of MoSe 2 NSs/CRF. The symmetric supercapacitor showed capacitance of 124F g −1 with an energy density of 8.5 W h Kg −1 at a power density of 264.8 W Kg −1 at a current density of 1 A g −1 . The superior electrochemical performances demonstrating that the MoSe 2 NSs/CRF has potential as an electrode material for energy storage application in high-performance supercapacitor fields.

Microscopic mechanism about the selective adsorption of Cr(VI) from salt solution on nitrogen-doped carbon aerogel microsphere pyrolysis products

A series of nitrogen-doped carbon aerogels (NCAs) were obtained through phase reaction polymerization and different carbonization temperatures to enhance adsorption efficacy of hexavalent chromium (Cr[VI]) from wastewater significantly. Factors that influence adsorption properties of carbon aerogel microspheres toward Cr(VI), such as pH, adsorbent content, initial Cr(VI) concentrations, and coexisting anion, were investigated. Three isotherm (Langmuir, Freundlich, and Sips) and three kinetic (pseudofirst-order, pseudosecond-order, and Elovich) models were used to interpret the adsorption process. The adsorption capacity of Cr(VI) reached 180.62 mg·g−1, which was superior to that of most aerogel adsorbents. In addition to the adsorption effect, the XPS results also showed that N-containing groups on the NCA surface reduce the adsorbed Cr(VI) to the less toxic Cr(III). The prepared sorbent demonstrates a negligible loss in adsorption capacity after 6 cycles. NCAs show acceptable application prospects in selective removal of Cr(VI) ions.

NiO/Carbon Aerogel Microspheres with Plum-Pudding Structure as Anode Materials for Lithium Ion Batteries.

To enhance the electrochemical performance of nickel oxide as anode materials for lithium ion batteries, NiO/carbon aerogel microspheres with a plum-pudding structure were designed and prepared by a sol-gel technique followed by two calcination processes under different atmospheres. Carbon aerogel microspheres (pudding) can act as a buffering and conductive matrix to enhance the structural stability and conductivity of the embedded NiO particles (plums), which are quite advantageous to the cycling performance and rate capability. Consequently, NiO/carbon aerogel microspheres with a plum-pudding structure deliver an initial charge capacity of 808 mAh g−1 and a reversible capacity retention of 85% after 100 cycles. The enhancement in electrochemical performance relative to pure NiO microspheres suggests that the design of a plum-pudding structure is quite effective.

Reverse Microemulsion Synthesis of Mesopore Phloroglucinol‐Resorcinol‐Formaldehyde Carbon Aerogel Microsphere as Nano‐Platinum Catalyst Support for ORR

AbstractCarbon aerogel (CA) microspheres are modified CA materials that can be prepared by reverse microemulsion and ambient pressure drying and without solvent exchanged. However, mesopore size of traditional resorcinol‐formaldehyde (RF) carbon aerogel microsphere is too small (3‐5 nm) to support nano‐platinum catalyst. In this study, we utilize reverse microemulsion polymerization and ambient pressure drying to develop a series of phloroglucinol‐resorcinol‐formaldehyde (PRF) carbon aerogel microspheres. These carbon aerogel microspheres possess large mesopore size (10–30 nm) and high specific surface area (1300–2000 m2 g−1). Compared with commercial Pt/C, the PRF carbon aerogel as nano‐platinum catalyst support shows the better and durable catalytic activity. The initial mass and electrochemical active surface area of the best performance of Pt/CA are 2.9 and 2.8 times higher than that of commercial Pt/C respectively. After the accelerated stability test (ADT), Pt/CA still keeps a mass and electrochemical active surface area up to 0.15 A mg−1 and 86.4 m2 g−1, while the commercial Pt/C lost to 0.02 A mg−1 and 42.8 m2 g−1. The stability of Pt/CA shows about 7.5 times enhancements compared to commercial Pt/C.

Enhanced capacitive performance by improving the graphitized structure in carbon aerogel microspheres.

Herein, good electrical conductivity and high specific surface area carbon aerogel (CA) microspheres were synthesized by a facile and economical route using a high temperature carbonization and CO2 activation method. The electroconductive graphitized structure of the CA microspheres could be easily improved by increasing the carbonization temperature. Then the CA microspheres were activated with CO2 to increase the specific surface area of the electrode material for electric double layer capacitors (EDLC). The sample carbonized at 1500 °C for 0.5 h and CO2 activated at 950 °C for 8 h showed an acceptable specific surface area and excellent cycle performance and rate capability for EDLC: 98% of the initial value of the capacitance was retained after 10 000 cycles, a specific capacitance of 121 F g−1 at 0.2 A g−1 and 101 F g−1 at 2 A g−1.

Phosphorus-modified porous carbon aerogel microspheres as high volumetric energy density electrode for supercapacitor

Electrode materials with high volumetric capacity are highly desired to improve the energy storage performance for the next generation supercapacitor. The loading density of active materials and potential window are the two keys to realizing the maximization of volumetric capacity. Herein, carbon aerogel microspheres (CAMs) with uniform spherical structure and high loading density are prepared by an emulsion polymerization without freeze/supercritical drying step. The CAMs are further treated with H3PO4, which not only optimize their pore structure for facilitating ion diffusion but also introduce phosphorus species to carbon skeleton for blocking active oxidation sites. Owing to the high loading density and the suppressed formation of unstable oxygen species by phosphorus, the optimal sample shows a good volume energy density of 48.1 Wh L−1 under a high applied potential difference of 3.3 V in 1M TEABF4/PC electrolyte. Our work presents a new direction for the developing of high volumetric energy density supercapacitors.

Sulfur-impregnated disordered SnO2/carbon aerogel core–shell microspheres cathode for lithium-sulfur batteries

It is extremely critical to prevent the loss of sulfur active material and shuttle reaction of polysulfide through into electrolyte in high-performance lithium-sulfur batteries. In this paper, we reported sulfur-impregnated SnO2/carbon aerogel core–shell microspheres as a polysulfide adsorbent for lithium-sulfur battery. The core of carbon aerogel microspheres is able to accommodate increasing volume and the shell of SnO2 works as high-efficiency polysulfide trap for the flexible structure of SnO2/carbon aerogel core–shell microspheres at full capacity. The obtained core–shell cathodes demonstrate significantly improved electrochemical performance (949 mAh g−1 at 0.1C). The capacities are remain 785 mAh g−1 over 80 cycles and high capacity retention of 76.9%. This positive result is owing to unique structure of core–shell microspheres with fast ion/electron transfer path and good structural stability.

Remarkable hydrogen storage properties and mechanisms of the shell–core MgH2@carbon aerogel microspheres

Carbon aerogel (CA) microspheres with highly crumpled graphene–like sheets surface and network internal structure have been successfully prepared by an inverse emulsion polymerization routine, subsequently ball milled with Mg powder to fabricate Mg@CA. The Mg change into MgH2 phases, decorating on the surface of the CA forming MgH2@CA microspheres composite after the hydrogenation process at 400 °C. The MgH2@CA microspheres composite displays MgH2–CA shell–core structure and shows enhanced hydrogenation and dehydrogenation rates. It can quickly uptake 6.2 wt% H2 within 5 min at 275 °C and release 4.9 wt% H2 within 100 min at 350 °C, and the apparent activation energy for the dehydrogenation is decreased to 114.8 kJ mol−1. The enhanced sorption kinetics of the composite is attributed to the effects of the in situ formed MgH2 NPs during the hydrogenation process and the presence of CA. The nanosized MgH2 could reduce the hydrogen diffusion distance, and the CA provides the sites for nucleation and prevents the grains from agglomerating. This novel method of in situ producing MgH2 NPs on zero–dimensional architecture can offer a new horizon for obtaining high performance materials in the hydrogen energy storage field.

Structural evolution of carbon aerogel microspheres by thermal treatment for high–power supercapacitors

In this work, a series of carbon aerogel microspheres (CAMs) with tailored pore structures were successfully prepared via a sol–gel method and subsequent heat–treatment at various temperatures from 600 to 1600 °C. The effects of heat–treatment temperature (HTT) on the CAM microstructure were systematically investigated by physical and chemical characterization. The electrical conductivity increased by up to 250 S/cm and mesopores with high electrolyte accessibility developed in the CAM with increasing HTT. However, the specific surface area (SSA) decreased for HTTs from 1000 to 1600 °C. The results show that these two factors should be finely balanced for further applications in high power supercapacitors. The CAMs carbonized at 1000 °C had the highest SSA (1454 m2/g), large mesoporous content (20%) and favorable conductivity (71 S/cm). They delivered a high energy density of 38.4 Wh/kg at a power density of 0.17 kW/kg. They retained an energy density of 25.5 Wh/kg even at a high power density of 10.2 kW/kg, and a good rate capability of 84% after 10,000 cycles. This performance is superior to, or at least comparable to, those of most reported carbon materials.

Capacitive deionization of NaCl solutions with ambient pressure dried carbon aerogel microsphere electrodes

We first used carbon aerogel microspheres prepared via emulsion polymerization and ambient drying techniques as electrode material for capacitive deionization.

High-performance all-solid state asymmetric supercapacitor based on Co3O4 nanowires and carbon aerogel

An all-solid state asymmetric supercapacitor has been fabricated using carbon aerogel (CA) microspheres as the negative electrode and Co3O4 nanowires on nickel foam (Co3O4–NF) as the positive electrode separated by PVA-KOH membrane as the electrolyte. For the desirable porous structure, high specific capacitance and rate capability of CA and Co3O4–NF, broader potential window of the two electrodes, no binder and conductive agent added, the asymmetric supercapacitor can be cycled reversibly in a wide potential window of 0–1.5 V with an energy density of 17.9 Whkg−1 at a power density of 750 W kg−1. The energy density of the asymmetric supercapacitor is significantly improved in comparison with those of the symmetric supercapacitors based on CA (6.28 Whkg−1) and Co3O4–NF (2.42 Whkg−1). The asymmetric supercapacitor can also deliver a high energy density of 10.44 Whkg−1, even at a high power density of 7.5 kW kg−1. In addition, the asymmetric device shows good stability with approximately 85% of its initial capacitance after 1000 cycles.

Preparation of carbon aerogel microspheres by a simple-injection emulsification method

Carbon aerogel microspheres were successfully prepared using a simple-injection emulsification method, employing sol–gel polycondensation of a resorcinol–formaldehyde solution containing sodium carbonate as a catalyst. This process was followed by solvent exchange using acetone, supercritical drying with carbon dioxide and carbonization in a nitrogen atmosphere. The effect of curing time before starting injection, injection rate and agitation rate of continuous phase on the particle size and the porous properties of the carbon aerogel microspheres was investigated. Adsorption of phenol by using the prepared carbon aerogel microspheres was also examined. The diameter of carbon aerogel microspheres was controlled in the range of 20–55μm by varying injection rate and agitation rate. The mean diameter of carbon aerogel microspheres decreased with increasing the injection rate and the agitation rate, whereas their mean diameter was independent of the curing time. The BET surface area and total pore volume of carbon aerogel microspheres increased with increasing the curing time. In contrast, their BET surface area and total pore volume decreased with increasing the injection rate and the agitation rate. The BET surface area, total pore volume, mesopore volume and micropore volume of the carbon aerogel microspheres with a mean diameter of 45μm were 903m2/g, 0.60cm3/g, 0.31cm3/g and 0.27cm3/g, respectively. The phenol-adsorption capacity of these carbon aerogel microspheres was 29.3mg phenol/g adsorbent.

Preparation and performances of carbon aerogel microspheres for the application of supercapacitor

Carbon aerogel (CA) microspheres were successfully synthesized by an inverse emulsion polymerization routine. Morphology and physical properties of the CA microspheres were characterized by scanning electron microscopy, N2 sorption isotherm, and transmission electron microscopy. The results showed that the CA microspheres were all fine spheres with diameters about 4 μm, and the CA microsphere was a typical mesoporous material with ordered mesoporous nano-network structure. The maximum capacitance of the electrode obtained from cyclic voltammetry was 187.08 F/g and the capacitance of the supercapacitor resulted from galvanostatic charge–discharge tests was up to 45.98 F/g. The supercapacitor using CA microsphere as electrode material presented a long cycle life, high charge–discharge efficiency, and low R s of 0.70 Ω in 6 M KOH electrolyte.

Characterization of the microstructures of organic and carbon aerogels based upon mixed cresol–formaldehyde

Organic aerogels were synthesized via the sol–gel polycondensation of mixed cresol with formaldehyde in a slightly basic aqueous solution followed by supercritical drying with carbon dioxide. Carbon aerogels are generated by pyrolysis of organic aerogels in inert atmosphere at high temperature. Obvious chemical and physical changes can take place within aerogel microstructures during the pyrolysis process. IR combined with TGA, TEM, and nitrogen adsorption is employed to study these changes in detail. Appreciable transformation of aerogel structure occurs during 250–600°C, which results from the release of water,organic groups and simultaneous rearrangement of aromatic rings. A new band occurring at 874 cm −1 in IR spectra after 400°C is associated with the IR-active vibration states of graphitic structure. With the increase of pyrolysis temperature, the density, surface area and total volume of aerogels keep increasing; on the contrary, the pore size distribution becomes narrower and the pore size decreases. The carbon aerogel microspheres are smaller than their organic aerogel precursors as a result of shrinkage during pyrolysis, as seen from TEM results.