UCLA

Green chemistry encompasses a broad range of topics that enable us to understand and address major environmental issues. This dissertation advances multiple green chemistry topics through three independent projects: 1) Development of boron cluster-based cathode materials for use in developing a new approach to lithium-ion based energy storage. 2) Application of a quantitative probing technique for kinetic isotope effects, using the dual-clumped isotope proxy, to evaluate dissolved inorganic carbon transformation at geological sites being considered for use as CO2 storage sinks. 3) Advancing dual clumped isotopes as a next-generation probing technique to determine if terrestrial cave carbonate samples can be used to study climate through palaeothermometry and study kinetic isotope effects in speleothems.

Novel boron-cluster based molecules were synthesized for use as cathodes in lithium-ion batteries. The B12(OC7H6COOH)12 cluster exhibited the greatest potential for use as a cathode material in lithium-ion batteries. This novel molecule served as a scaffold for post-modification to enhance cyclability in the solid state. B12(OC7H6COOLi)12, a derivative of B12(OC7H6COOH)12, was deemed compatible with cell design and reversibly cycled for one redox event at an E1/2 of 3.4 V vs Li/Li+ in an in situ swagelock cell setup. However, this cluster suffered from specific capacity issues associated with only one (out of 2) reversible redox event and a high molecular weight relative to traditional metal oxides used in current generation cells.

CaCO3 samples recovered from The Cedars, peridotite-associated springs located in Northern California, were analyzed using the novel dual clumped isotope proxy to evaluate CO2 transformation processes and kinetic isotope effects and biases. Surface floe samples begin to precipitate out of solution within the first hour of CO2 absorption, and the DIC pool requires a residence time of approximately 100 hours to achieve isotopic equilibria. The D47/D48 slope of samples from the Cedars (-2.803�0.500; 1.s.e.) agrees with published values from lab experiments designed to constrain CO2 hydrolysis-related kinetic fractionation (-2.911�0.200). Ancient travertine samples that are close to equilibrium in the D47-D48 space yield an average temperature of 8.3�1.1 �C, suggesting that the conditions during that time were approximately 10�C colder than present day temperature. The consistency of slopes in the multi-isotope space suggests the D47-D48 dual carbonate clumped isotope framework can be applied to study CO2-absorption processes in applied systems including sites of interest for geological sequestration.

CaCO3 samples from terrestrial cave sites at 13 localities from around the world were analyzed using dual clumped isotope (D47-D48) system. Data showed that 27 samples exhibited isotopic equilibrium with the majority having D47-T predicted temperatures matching measured temperatures. 17 samples exhibited isotopic disequilibria in the D47-D48 space. Of the latter suite of samples, 15 fell within quadrant 3, 1 within quadrant 2, and 1 within quadrant 1 in the DD47-DD48 space. Samples that fell within quadrant 2 exhibited traditional degassing disequilibria consistent with previous speleothem studies. Samples which fell within quadrants 1 and 3 were identified to have oxygen and carbon isotope exchange within the Rayleigh distillation model approach, however the specific type of exchange could only be resolved in the DD47-DD48 space. Samples within quadrant 1 were identified to have oxygen isotope exchange while samples within quadrant 3 had carbon isotope exchange. Cave raft samples collected from Mexico exhibited the largest carbon isotope exchange phenomenon with magnitudes of disequilibria into quadrant 3 correlating to the relative ventilation from caves that they were recovered from. This study suggests the D47-D48 dual carbonate clumped isotope framework can be applied to varying types of cave carbonate samples enabling quick identification of (dis)equilibria for use in paleoclimate reconstruction applications.