B.P. McGrail

In Situ One-Step Synthesis of Hierarchical Nitrogen-Doped Porous Carbon for High-Performance Supercapacitors

A hierarchically structured nitrogen-doped porous carbon is prepared from a nitrogen-containing isoreticular metal-organic framework (IRMOF-3) using a self-sacrificial templating method. IRMOF-3 itself provides the carbon and nitrogen content as well as the porous structure. For high carbonization temperatures (950 °C), the carbonized MOF required no further purification steps, thus eliminating the need for solvents or acid. Nitrogen content and surface area are easily controlled by the carbonization temperature. The nitrogen content decreases from 7 to 3.3 at % as carbonization temperature increases from 600 to 950 °C. There is a distinct trade-off between nitrogen content, porosity, and defects in the carbon structure. Carbonized IRMOFs are evaluated as supercapacitor electrodes. For a carbonization temperature of 950 °C, the nitrogen-doped porous carbon has an exceptionally high capacitance of 239 F g(-1). In comparison, an analogous nitrogen-free carbon bears a low capacitance of 24 F g(-1), demonstrating the importance of nitrogen dopants in the charge storage process. The route is scalable in that multi-gram quantities of nitrogen-doped porous carbons are easily produced.

Fluorocarbon adsorption in hierarchical porous frameworks

Metal-organic frameworks comprise an important class of solid-state materials and have potential for many emerging applications such as energy storage, separation, catalysis and bio-medical. Here we report the adsorption behaviour of a series of fluorocarbon derivatives on a set of microporous and hierarchical mesoporous frameworks. The microporous frameworks show a saturation uptake capacity for dichlorodifluoromethane of >4 mmol g(-1) at a very low relative saturation pressure (P/Po) of 0.02. In contrast, the mesoporous framework shows an exceptionally high uptake capacity reaching >14 mmol g(-1) at P/Po of 0.4. Adsorption affinity in terms of mass loading and isosteric heats of adsorption is found to generally correlate with the polarizability and boiling point of the refrigerant, with dichlorodifluoromethane > chlorodifluoromethane > chlorotrifluoromethane > tetrafluoromethane > methane. These results suggest the possibility of exploiting these sorbents for separation of azeotropic mixtures of fluorocarbons and use in eco-friendly fluorocarbon-based adsorption cooling.

Adsorption Kinetics in Nanoscale Porous Coordination Polymers

Nanoscale porous coordination polymers were synthesized using simple wet chemical method. The effect of various polymer surfactants on colloidal stability and shape selectivity was investigated. Our results suggest that the nanoparticles exhibited significantly improved adsorption kinetics compared to bulk crystals due to decreased diffusion path lengths and preferred crystal plane interaction.

Application of the Pressurised Unsaturated Flow (PUF) Test for Accelerated Ageing of Waste Forms

The pressurised unsaturated flow (PUF) test method is an emerging technique for studying the long-term durability or weathering of waste forms and other geologic materials. We have used the technique to monitor the complex coupling between primary phase dissolution, secondary phase precipitation and unsaturated flow behaviour, including changes in the hydraulic properties of the materials. New experimental data with low-activity waste glasses has shown that the technique effectively accelerates the hydrolysis and ageing processes by as much as 50 times over conventional static tests run at the same temperature. Rapid, sustained increases in the corrosion rate of three low-activity waste glasses were detected with the PUF technique in only a few days that required months to observe in static experiments. The ability to quickly detect long-term performance problems with waste forms may make it possible to formulate second generation materials concurrently with meaningful long-term durability screening.

Competitive adsorption study of CO2 and SO2 on CoII3[CoIII(CN)6]2 using DRIFTS

Diffuse reflectance infrared Fourier transform spectroscopy was used to study the competitive adsorption of CO(2) and SO(2) on the cobalt Prussian blue analogue Co(II)(3)[Co(III)(CN)(6)](2) at 298 K. Characteristic peaks for adsorbed CO(2) and SO(2) species were identified and their relative areas, measured simultaneously as a function of pressure at 298 K, varied in accordance with a Langmuir-Freundlich isotherm fitted to both gases in the low-coverage Henrys Law limit. Evidence for co-adsorption of trace water was also obtained, as well as the apparent formation of an analogous cobalt nitroprusside compound as a reaction product under certain conditions. The several aspects of the adsorption of CO(2) and SO(2) determined in this work point to an important role for real-time diffuse reflectance infrared measurements in adsorption studies, particularly in the case of competitive adsorption where the occurrence and fate of molecular-level markers arising from more than one adsorbed species can be monitored simultaneously. Depending on the application, this may more than offset certain quantitative limitations of the technique that confine measurements to a relatively narrow set of experimental conditions and demand careful consideration of the effects of sample preparation and treatment.

Numerically Simulating the Carbonate Mineralization of Basalt with the Injection of Supercritical Carbon Dioxide in Deep Saline Aquifers

The principal mechanisms for the geologic sequestration of carbon dioxide in deep saline aquifers include geological structural trapping, hydrological entrapment of nonwetting fluids, aqueous phase dissolution and ionization, and geochemical sorption and mineralization. In sedimentary saline aquifers the dominant mechanisms are structural and dissolution trapping, with moderate to weak contributions from hydrological and geochemical trapping; where, hydrological trapping occurs during the imbibition of aqueous solution into pore spaces occupied by gaseous carbon dioxide, and geochemical trapping is controlled by generally slow reaction kinetics. In addition to being globally abundant and vast, deep basaltic lava aquifers offer mineralization kinetics that make geochemical trapping a dominate mechanism for trapping carbon dioxide in these formations. For several decades the United States Department of Energy has been investigating Columbia River basalt in the Pacific Northwest as part of its environmental programs and options for natural gas storage. Recently this nonpotable and extensively characterized basalt aquifer is being reconsidered as a potential reservoir for geologic sequestration of carbon dioxide. The reservoir has an estimated storage capacity of 100 giga tonnes of carbon dioxide and comprises layered basalt flows with sublayering that generally alternates between low permeability massive and high permeability breccia. Chemical analysis of the formation shows 10 wt% Fe, primarily in the +2 valence. The mineralization reaction that makes basalt aquifers attractive for carbon dioxide sequestration is that of calcium, magnesium, and iron silicates reacting with dissolved carbon dioxide, producing carbonate minerals and amorphous quartz. Preliminary estimates of the kinetics of the silicate-to-carbonate reactions have been determined experimentally and this research is continuing to determine effects of temperature, pressure, rock composition and mineral assemblages on the reaction rates. This study numerically investigates the injection, migration and sequestration of supercritical carbon dioxide in deep Columbia River basalt formations using the multifluid subsurface flow and reactive transport simulator STOMP-CO2. Simulations are executed on high resolution multiple stochastic realizations of the layered basalt systems and demonstrate the migration behavior through layered basalt aquifers and the mineralization of dissolved carbon dioxide. Reported results include images of the migration behavior, distribution of carbonate formation, quantities of injected and sequestered carbon dioxide, and percentages of the carbon dioxide sequestered by different mechanisms over time.