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Carbon Capture Methods Utilizing Organosulfur Compounds

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The US National Academy of Sciences and The Royal Society have recently released a detailed report on the causes and effects of global climate change.1 This report states that

The US National Academy of Sciences and The Royal Society have recently released a detailed report on the causes and effects of global climate change.1 This report states that the Earth’s climate is rapidly changing due to human activity. Specifically, the burning of fossil fuels to satisfy the energy demands of rising global population has resulted in unprecedented levels of greenhouse gasses in the atmosphere. These high levels of greenhouse gasses are serving to warm the surface of the planet resulting in extreme weather events. Thus, controlling the atmospheric CO2 level is motivating a great deal of scientific research in the area of carbon capture and storage (CCS).

Despite the great strides being made in the areas of alternative energy and solar-energy conversion, consumption of fossil fuels for energy generation will likely continue into the foreseeable future. This is primarily motivated by economic factors inasmuch as fossil fuels are a proven resource base with robust harvesting and distribution infrastructure.2 Presently, there are more than 8,000 stationary CO2 emission sources with an annual output of 13,466 megatons of CO2 per year.2 In this context, development of systems that ameliorate the output of greenhouse gasses from stationary CO2 sources, such as coal and natural gas burning power plants, is urgently needed.

In this document the utility of sulfur nucleophiles for CCS schemes is explored. The main thrust of the research has been utilizing electrogenerated sulfur nucleophiles to capture CO2, which can be electrochemically recovered from the resulting thiocarbonates while concomitantly regenerating the masked capture agent. Further, a temperature swing CO2 capture scheme that employs benzylthiolate as the CO2 sorbent is proposed and methods of manipulating the release temperature and kinetics were investigated. These reports represent the first application of organosulfur compounds toward CCS technologies and there are a number of newly reported compounds. The appendix deviates from the theme of the first four chapters to describe the functionalization of poly(2,6-dimethyl-1,4-phenylene oxide) with ferrocene moieties by the copper catalyzed azide-alkyne coupling reaction. This material is discussed within the context of anion recognition and sensing applications.

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Date Created
  • 2018

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The synthesis and characterization of ionic liquids for alkali-metal batteries and a novel electrolyte for non-humidified fuel cells

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This thesis focused on physicochemical and electrochemical projects directed towards two electrolyte types: 1) class of ionic liquids serving as electrolytes in the catholyte for alkali-metal ion conduction in batteries

This thesis focused on physicochemical and electrochemical projects directed towards two electrolyte types: 1) class of ionic liquids serving as electrolytes in the catholyte for alkali-metal ion conduction in batteries and 2) gel membrane for proton conduction in fuel cells; where overall aims were encouraged by the U.S. Department of Energy.

Large-scale, sodium-ion batteries are seen as global solutions to providing undisrupted electricity from sustainable, but power-fluctuating, energy production in the near future. Foreseen ideal advantages are lower cost without sacrifice of desired high-energy densities relative to present lithium-ion and lead-acid battery systems. Na/NiCl2 (ZEBRA) and Na/S battery chemistries, suffer from high operation temperature (>300ºC) and safety concerns following major fires consequent of fuel mixing after cell-separator rupturing. Initial interest was utilizing low-melting organic ionic liquid, [EMI+][AlCl4-], with well-known molten salt, NaAlCl4, to create a low-to-moderate operating temperature version of ZEBRA batteries; which have been subject of prior sodium battery research spanning decades. Isothermal conductivities of these electrolytes revealed a fundamental kinetic problem arisen from "alkali cation-trapping effect" yet relived by heat-ramping >140ºC.

Battery testing based on [EMI+][FeCl4-] with NaAlCl4 functioned exceptional (range 150-180ºC) at an impressive energy efficiency >96%. Newly prepared inorganic ionic liquid, [PBr4+][Al2Br7-]:NaAl2Br7, melted at 94ºC. NaAl2Br7 exhibited super-ionic conductivity 10-1.75 Scm-1 at 62ºC ensued by solid-state rotator phase transition. Also improved thermal stability when tested to 265ºC and less expensive chemical synthesis. [PBr4+][Al2Br7-] demonstrated remarkable, ionic decoupling in the liquid-state due to incomplete bromide-ion transfer depicted in NMR measurements.

Fuel cells are electrochemical devices generating electrical energy reacting hydrogen/oxygen gases producing water vapor. Principle advantage is high-energy efficiency of up to 70% in contrast to an internal combustion engine <40%. Nafion-based fuel cells are prone to carbon monoxide catalytic poisoning and polymer membrane degradation unless heavily hydrated under cell-pressurization. This novel "SiPOH" solid-electrolytic gel (originally liquid-state) operated in the fuel cell at 121oC yielding current and power densities high as 731mAcm-2 and 345mWcm-2, respectively. Enhanced proton conduction significantly increased H2 fuel efficiency to 89.7% utilizing only 3.1mlmin-1 under dry, unpressurized testing conditions. All these energy devices aforementioned evidently have future promise; therefore in early developmental stages.

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Date Created
  • 2014

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Characterizing nanomaterials and protic ionic liquids utilizing nuclear magnetic resonance spectroscopy

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Structural details of phosphonic acid functionalized nanomaterials and protic ionic liquids (PILs) were characterized using nuclear magnetic resonance (NMR) spectroscopy. It is well known that ligands play a critical

Structural details of phosphonic acid functionalized nanomaterials and protic ionic liquids (PILs) were characterized using nuclear magnetic resonance (NMR) spectroscopy. It is well known that ligands play a critical role in the synthesis and properties of nanomaterials. Therefore, elucidating the details of ligand-surface and ligand-ligand interactions is crucial to understanding nanomaterial systems more completely.

In an effort to further the understanding of ligand-surface interactions, a combination of multi-nuclear (1H, 29Si, 31P) and multi-dimensional solid-state NMR techniques were utilized to characterize the phosphonic acid functionalization of fumed silica nanoparticles using methyl phosphonic acid (MPA) and phenyl phosphonic acid (PPA). Quantitative 31P MAS solid-state NMR measurements indicate that ligands favor a monodentate binding mode. Furthermore, 1H-1H single quantum-double quantum (SQ-DQ) back-to-back (BABA) 2D NMR spectra of silica functionalized with MPA and PPA indicate that the MPA and PPA are within 4.2±0.2 Å on the surface of the nanomaterial.

The ligand capping of phosphonic acid (PA) functionalized CdSe/ZnS core-shell quantum dots (QDs) was investigated with a combination of ligand exchange, solution and solid-state 31P NMR spectroscopy. In order to quantify the ligand populations on the surface of the QDs, ligand exchange facilitated by PPA resulted in the displacement of the PAs, and allowed for quantification of the free ligands using 31P liquid state NMR.

In addition to characterizing nanomaterials, the ionicity and transport properties of a series of diethylmethylamine (DEMA) based protic ionic liquids (PILs) were characterized, principally utilizing NMR. Gas phase proton affinity was shown to be a better predictor for the extent of proton transfer, and in turn the ionicity of the PIL, than using ∆pKa. Furthermore, pulsed field gradient (PFG) NMR was used to determine that the exchangeable proton diffuses with the cation or the anion based on the strength of the acid used to generate the PILs.

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Date Created
  • 2015