CO₂ Adsorption on Carbon Models of Organic Constituents of Gas Shale and Coal

Imperfections of the organic matrix in coal and gas shales are modeled using defective and defect-free graphene surfaces to represent the structural heterogeneity and related chemical nature of these complex systems. Based upon previous experimental investigations that have validated the stability and existence of defect sites in graphene, plane-wave electronic density functional theory (DFT) calculations have been performed to investigate the mechanisms of CO2 adsorption. The interactions of CO2 with different surfaces have been compared, and the physisorption energy of CO2 on the defective graphene adsorption site with one carbon atom missing (monovacancy) is approximately 4 times as strong as that on a perfect defect-free graphene surface, specifically, with a physisorption energy of ∼210 meV on the monovacancy site compared to ∼50 meV on a perfect graphene surface. The energy associated with the chemisorption of CO2 on the monovacancy site is substantially stronger at ∼1.72 eV. Bader charge, density of states, and vibrational frequency estimations were also carried out and the results indicate that the CO2 molecule binds to the surface becoming more stable upon physisorption onto the monovacancy site followed by the original CO bonds weakening upon CO2 chemisorption onto the vacancy site

Molecular Simulation Studies of CO₂ Adsorption by Carbon Model Compounds for Carbon Capture and Sequestration Applications

Effects of oxygen-containing surface functionalities on the adsorption of mixtures including CO2/CH4, CO2/N2, and CO2/H2O have been investigated in the current work. Together with Bader charge analysis, electronic structure calculations have provided the initial framework comprising both the geometry and corresponding charge information required to carry out statistical-based molecular simulations. The adsorption isotherms and selectivity of CO2 from CO2/N2, CO2/CH4, and CO2/H2O gas mixtures were determined by grand canonical Monte Carlo simulations at temperature/pressure conditions relevant to carbon capture and sequestration applications. The interactions between the surfaces with induced polarity and nonpolar/polar molecules have been investigated. It has been observed that, due to the induced polarity of the surface functionalization, the selectivity of CO2 over CH4 increases from approximately 2 to higher than 5, and the selectivity of CO2 over N2 increases from approximately 5 to 20, especially in the low-pressure regime. However, water vapor will always preferentially adsorb over CO2 in carbon-based systems containing oxygen functionalized surfaces at conditions relevant to carbon capture application. Molecular simulation results indicate that the surface chemistry in micropores is tunable thereby influencing the selectivity for enhanced uptake of CO2

Media 4: Flow-assisted Single-beam Optothermal Manipulation of Microparticles

Originally published in Optics Express on 16 August 2010 (oe-18-17-18483

Media 3: Flow-assisted Single-beam Optothermal Manipulation of Microparticles

Originally published in Optics Express on 16 August 2010 (oe-18-17-18483

Media 1: Flow-assisted Single-beam Optothermal Manipulation of Microparticles

Originally published in Optics Express on 16 August 2010 (oe-18-17-18483

Effects of Surface Heterogeneity on the Adsorption of CO₂ in Microporous Carbons

Carbon capture combined with utilization and storage has the potential to serve as a near-term option for CO₂ emissions reduction. CO₂ capture by carbon-based sorbents and CO₂ storage in geologic formations such as coal and shale both require a thorough understanding of the CO₂ adsorption properties in microporous carbon-based materials. Complex pore structures for natural organic materials, such as coal and gas shale, in addition to general carbon-based porous materials are modeled as a collection of independent, noninterconnected, functionalized graphitic slit pores with surface heterogeneities. Electronic structure calculations coupled with van der Waals-inclusive corrections have been performed to investigate the electronic properties of functionalized graphitic surfaces. With Bader charge analysis, electronic structure calculations can provide the initial framework comprising both the geometry and corresponding charge information required to carry out statistical modeling. Grand canonical Monte Carlo simulations were carried out to determine the adsorption isotherms for a given adsorbent–adsorbate interaction at temperature/pressure conditions relevant to carbon capture applications to focus on the effect of the surface functionalities. On the basis of the current work, oxygen-containing functional groups were predicted to enhance CO₂ adsorption in microporous carbon materials in the absence of water vapor, and the hydrated graphite was found to hinder CO₂ adsorption

Media 2: Flow-assisted Single-beam Optothermal Manipulation of Microparticles

Originally published in Optics Express on 16 August 2010 (oe-18-17-18483

Media 5: Flow-assisted Single-beam Optothermal Manipulation of Microparticles

Originally published in Optics Express on 16 August 2010 (oe-18-17-18483

The effect of the intervention on emotional vocabulary by group.

<p>The effect of the intervention on emotional vocabulary by group.</p