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Results for “nanoporous carbon”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2026

Extreme confinement of hydrogen gas within fullerenelike nanoporous carbon

Nanoporous carbons and carbon nanostructures can store hydrogen at cryogenic temperatures but lack the volumetric and gravimetric capacity to be industrially significant. Recent inelastic neutron scattering experiments suggest a highly dense phase of hydrogen at temperatures well above the melting point of solid hydrogen. However, it remains unclear how pore geometry and intermolecular interactions enable these dense phases to exist, with dispersion (van der Waals) or electrostatic/induction suggested to be the key effects in slit and curved pores but their relative contributions have yet to be quantified. In this paper, we perform benchmark electronic structure calculations allowing the interactions between planar and curved aromatic molecules with hydrogen to be accurately determined. Dispersion was found to dominate over electrostatic and inductive effects with some many-body charge transfer (Dobson type-A) effects needed to capture the most highly curved structures. Density functional methods that include type-A many-body effects were found to accurately describe the intermolecular interactions at a fraction of the cost of coupled-cluster simulations and these approaches were used to calculate the energies inside large carbon bowl and slit pores. The interaction energies inside the bowl pores were found to depend on the orientation of the hydrogen molecule. This rotational barrier, modeled as a quantum hindered rotor, could reproduce the peak splitting observed in inelastic neutron scattering experiments, with weak splitting arising from bowl-like fullerene pores and strong splitting from highly confining nanotubelike pores. Increasing the fraction of such curved pores in nanoporous carbons may therefore offer a pathway to enhance their hydrogen-storage capacity. Moreover, the preferential adsorption of ortho hydrogen on nanotubelike pores could enable the storage of high-density hydrogen without the need to remove heat produced during the ortho-para hydrogen conversion.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Partial breaking of the Coulombic ordering of ionic liquids confined in carbon nanopores

Ionic liquids are composed of equal quantities of positive and negative ions. In the bulk, electrical neutrality occurs in these liquids due to Coulombic ordering, in which ion shells of alternating charge form around a central ion. Their structure under confinement is far less well understood. This hinders the widespread application of ionic liquids in technological applications. Here we use scattering experiments to resolve the structure of a widely used ionic liquid (EMI–TFSI) when it is confined inside nanoporous carbons. We show that Coulombic ordering reduces when the pores can accommodate only a single layer of ions. Instead, equally charged ion pairs are formed due to the induction of an electric potential of opposite sign in the carbon pore walls. This non-Coulombic ordering is further enhanced in the presence of an applied external electric potential. Furthermore, this finding opens the door for the design of better materials for electrochemical applications.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Dual Functional Ni3S2@Ni Core-Shell Nanoparticles Decorating Nanoporous Carbon as Cathode Scaffolds for Lithium-Sulfur Battery with Lean Electrolytes

Lithium-sulfur batteries are very promising for next-generation energy storage. However, most studies use flooded electrolytes to achieve a high specific capacity at the expense of lowering the specific energy. Understanding lithium-sulfur battery performance with lean electrolytes is highly desirable. Herein, a modified Pechini method is developed to synthesize a nanoporous carbon host decorated with Ni3S2@Ni particles. Such a cathode delivers enhanced specific capacities with extended cycling life in lean electrolytes, due to the dual functions of the Ni3S2 shell, which can both facilitate reaction kinetics and promote electrolyte wetting. This work highlights a strategy to rationally design cathodes for highenergy lithium-sulfur batteries.

Zhang, Yulun↗
DOE OSTI2016

In-pore exchange and diffusion of carbonate solvent mixtures in nanoporous carbon

High resolution magic angle spinning (HRMAS) 1 H NMR spectroscopy has been used to resolve different surface and in-pore solvent environments of ethylene carbonate (EC) and dimethyl carbonate (DMC) mixtures absorbed within nanoporous carbon (NPC). Two dimensional (2D) 1 H HRMAS NMR exchange measurements revealed that the inhomogeneous broadened in-pore resonances have pore-to-pore exchange rates on the millisecond timescale. Pulsed-field gradient (PFG) NMR diffusometry revealed the in-pore self-diffusion constants for both EC and DMC were reduced by up to a factor of five with respect to the diffusion in the non-absorbed solvent mixtures.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Anomalous H 2 Desorption Rate of NaAlH 4 Confined in Nitrogen-Doped Nanoporous Carbon Frameworks

Confining NaAlH 4 in nanoporous carbon scaffolds is known to alter the sorption kinetics and/or pathways of the characteristic bulk hydride reactions through interaction with the framework at the interface, increased specific surface area of the resulting nanoparticles, decreased hydrogen diffusion distances, and prevention of phase segregation. Although the nanosize effects have been well studied, the influence of the carbon scaffold surface chemistry remains unclear. Here we compare the hydrogen sorption characteristics of NaAlH 4 confined by melt infiltration in nitrogen-doped/undoped ordered nanoporous carbon of two different geometries. 23 Na and 27 Al MAS NMR, N 2 sorption, and PXRD verify NaAlH 4 was successfully confined and remains intact in the carbon nanopores after infiltration. Both the N-doped/undoped nanoconfined systems demonstrate improved reversibility in relation to the bulk hydride during hydrogen desorption/absorption cycling. Isothermal kinetic measurements indicate a lowering of the activation energy for H 2 desorption by as much as 70 kJ/mol in N-doped frameworks, far larger than the reduction in carbon-only frameworks. Most interestingly, this dramatic lowering of the activation energy is accompanied by an unexpected and anomalously low NaAlH 4 desorption rate in the N-doped frameworks. This suggests that the framework surface chemistry plays an important role in the desorption process and that the rate limiting step for desorption may be associated with interactions of the hydride and host surface. Our results indicate that functionalization of carbon scaffold surface chemistry with heteroatoms provides a powerful method of altering the characteristic hydrogen sorption properties of confined metal hydride systems. Furthermore, this technique may prove beneficial in the path to a viable metal hydride-based hydrogen storage system.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Tailoring Pore Architecture and Heteroatom Functionality of Polymeric Waste-Derived Nanoporous Carbon for CO 2 Capture Applications

This study proposes upcycling polymeric waste, i.e., waste floral foam, into high-performance nanoporous carbon that efficiently captures CO 2 . This paper presents strategies for improving the properties of nanoporous carbon, which aid in a superior CO 2 capture performance. Initially, pristine nanoporous carbon was produced from waste floral foam using various KOH impregnation ratios. The nanoporous carbon with a 1:2 (waste floral foam:KOH) ratio exhibiting optimal CO 2 capture capability was further advanced through single and dual atom doping. The doping of N and codoping of N,S atoms into the nanoporous carbon altered its textural and surface chemical properties, making them efficient for CO 2 capture. Comparative CO 2 capture studies of pristine nanoporous carbon (NC-x), N-doped nanoporous carbon (N-NC2), and N,S-codoped nanoporous carbon (N,S-NC2) demonstrate the superiority of N-doping. N-doped nanoporous carbon exhibited the largest ultramicroporosity (0.3100 cm3/g, 63.43%) and highest heteroatom content (34.94 atomic %), contributing to its enhanced CO 2 capture capability (4.54 mmol/g). Finally, implementing the “waste-to-depollution” approach, this research lays the groundwork for producing low-cost, environmentally friendly nanoporous carbon with remarkable CO 2 capture attributes.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

Adsorptive recovery of neodymium and dysprosium in phosphorous functionalized nanoporous carbon

Here, phosphorus functionalized nanoporous carbon was synthesized from lignin by periodical reactions with potassium hydroxide and triphenylphosphine. It has the BET surface area of 837 m 2 /g and total pore volume 0.41 cm 3 /g along with 0.9 atom% phosphorus. The adsorption of neodymium (Nd (III)) and dysprosium (Dy(III)) were in the range of 335–344 mg/g upto their initial concentration of 500 ppm in water and such adsorption amount is higher than that of majority of the adsorbents reported in literature. The adsorption capacity showed negligible dependency on the solution pH. The distribution coefficients for Nd(III) and Dy(III) were within 1000 to 10,000 mL/g. The adsorption capacity of iron (Fe(III)) under the similar conditions was one order of magnitude lower and it suggests a possible separation of these rare earth elements from iron. The maximum selectivity of separation of Nd(III) and Dy(III) from iron was ca. 32 to 61. Kinetic study revealed that the adsorption of Dy was faster than that of Nd(III). The results of kinetic study were better fit with pseudosecond order kinetics. XPS studies on both Nd(III) and Dy(III)-adsorbed carbons revealed a small shift in the P 2p 3/2 energy level of phosphorus towards higher energy level hereby suggesting a possible formation of metallic phosphates. Additionally, Similar studies on Nd(III) and Dy(III)-adsorbed carbon indicated small amounts carbonates and oxides of rare earth elements that might have also been formed. In conculsion, the overall results suggest that this carbon can be used as a potential sorbent for enrichment and separation of Nd(III) and Dy(III).

36 MATERIALS SCIENCE↗
DOE OSTI2020

Revealing Molecular Mechanisms in Hierarchical Nanoporous Carbon via Nuclear Magnetic Resonance

Hierarchical nanoporous carbons (HNC) have been proven to be an effective adsorbent for the adsorption of volatile organic compounds (VOCs) and CO 2 . However, questions remain regarding the hierarchical structure regulation, the adsorption mechanisms of adsorbate uptake, and interactions within the HNC. Here, we synthesize HNC from wood, using a microwave-induced heating method incorporating K 2 CO 3 activation. Our HNC exhibit Murray's law multiscale structures, prompting a molecular-scale study of adsorbate adsorption via nuclear magnetic resonance (NMR). NMR chemical shifts are consistent with ring-current effects from the adsorbent. Our NMR technique provides a convenient way to quantitate adsorption of adsorbate in HNC. VOC vapor adsorption results show NMR chemical-shift changes with time, suggesting initial adsorption into mesopores, followed by diffusion into micropores. Schroeder's paradox is demonstrated by differences in observed shifts for adsorbed liquid vis-à-vis vapor phase in these HNC. These HNC show high CO 2 adsorption capacity, portending applications to carbon capture.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

Effect of ZnCl{sub 2} activation on CO{sub 2} adsorption of N-doped nanoporous carbons from polypyrrole

In this study, N-doping nanoporous carbons (NNCs) were prepared from polypyrrole (PPY) by ZnCl{sub 2} activation. The activation process was carried out under set conditions (PPY/ZnCl{sub 2}=1/4) at 300–800 °C for 2 h. With increasing activation temperature, the specific surface area and total pore volume of the NNCs increased significantly from 539 m{sup 2}/g (300 °C) to 1268 m{sup 2}/g (700 °C) and from 0.245 cm{sup 3}/g (300 °C) to 0.561 cm{sup 3}/g (700 °C), respectively. In addition, the use of PPY carbon precursors allowed the integration of high N content (9.28 wt%) and resulted in a large narrow micropore distribution (<1 nm) in the prepared NNCs. The CO{sub 2} adsorption isotherms showed that PZ-600 exhibited the best CO{sub 2} adsorption capacity of 167 mg/g at 1 bar and 25 °C when the activation temperature was 600 °C. - Graphical abstract: CO{sub 2}/298 K adsorption/desorption isotherms of the N-enriched porous carbons. - Highlights: • N-doping nanoporous carbons were prepared from polypyrrole by ZnCl{sub 2} activation. • Through ZnCl{sub 2} activation, the specific surface area and total pore volume increased. • PZ-600 exhibited the best CO{sub 2} adsorption capacity of 167 mg/g at 1 bar and 25 °C.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2013

Ordered nanoporous carbon for increasing CO{sub 2} capture

Ordered nanoporous carbons (ONCs) were prepared using a soft-templating method. The prepared ONCs materials were subjected to a controlled carbonization temperature over the temperature range, 700-1000 Degree-Sign C, to increase the specific surface area and total pore volume of ordered nanoporous carbon followed by carbonization of the phenolic resin. ONCs materials synthesized at various carbonization temperatures were used as adsorbents to improve the CO{sub 2} adsorption efficiency. The surface properties of the ONCs materials were examined by X-ray photoelectron spectroscopy. The structural properties of the ONCs materials were analyzed by X-ray diffraction. The textural properties of the ONCs materials were examined using the N{sub 2}/77 K adsorption isotherms according to the Brunauer-Emmett-Teller equation. The CO{sub 2} adsorption capacity was measured by CO{sub 2} isothermal adsorption at 298 K/30 bar and 298 K/1 bar. The carbonization temperature was found to have a major effect on the CO{sub 2} adsorption capacity, resulting from the specific surface area and total pore volumes of the ONCs materials. - Graphical abstract: This schematic diagram described synthesis of ONCs. Highlights: Black-Right-Pointing-Pointer ONCs materials can be prepared readily using the direct-triblock-copolymer-templating method. Black-Right-Pointing-Pointer The distributions show that prominent development can be observed around the micro-pore region. Black-Right-Pointing-Pointer The soft-templating method provides opportunities for controlling the pore structure of ONCs. Black-Right-Pointing-Pointer From thermal power plants for CO2 capture by adsorption technology, is a new direction.

36 MATERIALS SCIENCE↗