Development and analysis of novel functional materials for energy and gas storage applications

Abstract

For the last decade, the increasing carbon dioxide ($CO_2$) emission from burning fossil fuels has been regarded as one of the main origins for various energy and environmental issues. To resolve both grand challenges, the global $CO_2$ level decrease and efficient energy storage are essential as short- and long-term solutions, respectively. In this thesis, I cover the development and analysis of novel functional materials for energy and gas storage applications.

In Chapter 2, restacking-inhibited 3D reduced graphene oxides were developed for electrical double layer capacitors (EDLCs), one of the energy storage systems (ESSs). Having noticed that the intercalated water molecules between graphene oxide interlayers play a critical role for the restacking of graphene sheets, in this study, these restacking phenomena were effectively mitigated by functionalizing the surface of graphene oxides, thus consequently, verifying the effect of restacking-inhibition on electrochemical performances.

In Chapter 3, multicomponent transition metal (TM) oxides were synthesized and evaluated as pseudocapacitor electrodes. The roles of crystal defects, formed by solid-solution mixing of TMs, could be elucidated by the combined X-ray absorption fine structure (XAFS) analyses and density functional theory (DFT) calculations.

In Chapter 4, TM-based $\alpha$ -layered double hydroxides (LDHs) were utilized as pseudocapacitor electrodes. While $\alpha$ -LDHs exhibited excellent electrochemical activities, mainly originating from its unique layered structures, they also possessed the vulnerable $\alpha -to- \beta$ phase transition, thus undergoing the severe capacity decay. Based on the crystal field theories, the solid solution mixing of binary TM ions is able to allow $\alpha$ -LDHs to possess the sustainable cycling performance without sacrificing the original high capacity.

In Chapter 5, porous activated carbons from recycling coffee bean dreg were synthesized for dry $CO_2$ sorbents. Through the varied porosity condition, the dependence of the overall $CO_2$ capture performance (absolute uptake, isosteric heat of adsorption, $CO_2/N_2$ selectivity) on pore size was verified.

In Chapter 6, the series of porous melamine resins with mesoscopic regularity were synthesized by a using the simple co-polymerization route. In this study, it was confirmed that the hydrogen bonding between resin monomers and surfactant molecules play a pivotal role for mesoscopic ordered structures. Based on this ordered mesoporous melamine resins, the general design principles for selective $CO_2$ captures over $N_2$ could be provided.