Bio-Inspired CO2 mineralization for the synthesis of metal oxides and their applications

Abstract

Calcium carbonate (CaCO3), which composes the exoskeleton of mollusk, is one of the widely researched materials. Vaterite, the least stable phase among crystalline CaCO3 polymorphs (i.e., vaterite, aragonite, and calcite), has received much attention due to its distinct properties such as high water-solubility, porosity, and surface area as well as biocompatibility. In this thesis, CaCO3 vaterite was stabilized by the introduction of dopamine, a catecholic adhesive molecule that mimics the key motif of mussel adhesive proteins and polymerizes spontaneously to polydopamine (PDA) during CaCO3 mineralization. Visible-light active nano-grained CeO2 sheets were successfully synthesized with PDA-induced CaCO3 vaterite. Nano-grained CeO2 sheets showed a red-shift of UV/Vis absorption spectra and a considerably narrowed band gap when compared with that of CeO2 nanoparticles. Nano-grained CeO2 sheets have shown significantly enhanced photocatalytic reaction with the enhanced rate for the degradation of methylene blue over commercial CeO2 nanoparticles under visible light irradiation. In addition, novel graphene/CuO hybrid materials were synthesized through inspiration from natural biomineralization for their application to lithium ion battery electrode. CuO possesses high theoretical capacity and safety with low cost and limited environmental toxicity, but a large volumetric change of CuO electrodes during the insertion and extraction of lithium ions can destroy its crystal structure and cause capacity decay in a short time. Graphene-wrapped CuO hybrid material could highly enhance the stability and recyclability of CuO anode for lithium ion batteries. Graphene/CuO was synthesized by converting a CO2-mineralized graphene oxide/CaCO3 precursor to Cu-based minerals. Graphene/CuO exhibited nanoribbon-like CuO aggregates well-hybridized with graphene nanosheets. The excellent electrochemical performance of graphene/CuO is attributed to the synergic effect of CuO wrapped by...