Synthesis of framework based 3D carbon materials and their applications.

Abstract

The research presented in this dissertation focuses on the synthesis and characterization of three-dimensional (3D) hybrid carbon materials using the Chemical Vapor Deposition (CVD) method under low pressure and temperature conditions, with acetone as the carbon source. The synthesized materials include graphene, graphene oxide (GO), and carbon nanotubes (CNTs), both single-wall and multi-wall, grown on zeolites and nickel foam as a scaffold structure. Comprehensive characterization techniques, including High-Resolution Scanning Electron Microscopy (HR-SEM), Transmission Electron Microscopy (TEM), X-ray Diffraction (XRD), and Brunauer-Emmett-Teller (BET) surface area analysis, were employed to validate the structure and properties of the synthesized carbon materials. The CVD method was successfully utilized to grow a hybrid carbon material composed of graphene, graphene oxide, and carbon nanotubes on nickel foam. Characterization confirmed the successful synthesis and structural integrity of the material. HR-SEM and TEM images revealed a well-interconnected network of carbon structures, while XRD patterns indicated the crystalline nature of the materials. BET surface area analysis demonstrated that the synthesized material exhibits a mixed porosity profile with both macropores and micropores, showing a significant surface area suitable for various applications. The use of zeolite as a scaffold proved effective in supporting the growth of carbon material. The removal of the zeolite template via hydrofluoric acid treatment resulted in a pure carbon structure with various morphologies. The removal of nickel foam with nitric acid treatment results in a soft oxidation of the carbon material, promoting the formation of graphene oxide.<br /> <br /> The obtained materials were applied in CO₂ filter adsorption and lithium-ion batteries as cathodes. To evaluate the adsorption capacities of HCM as carbon dioxide filter a dynamic adsorption system was developed in the laboratory. The adsorbent capacities of the hybrid carbon materials, the hybrid carbon materials with zeolite and zeolites alone were evaluated and compared with activated carbon. The comparison revealed a significant change of adsorption for the carbon material only and with zeolites. Only the group of materials synthesized with zeolite NH₄⁺Y show lower performance than activated carbon. It was possible to elucidate the kinetic behavior of the HCMs, by the uses of kinetic models based on adsorption. The fits adjust well with the experimental results. To evaluate the performance of the material as a cathode in lithium-ion batteries, it was mixed with agglomerating and conducting agents. The mixture was then spread on aluminum foil, dried, and cut into the desired shape. A CR2032 coin cell was assembled to assess the conductive properties of the material. The coin cell underwent 1000 charge-discharge cycles and was characterized using Electrochemical Impedance Spectroscopy (EIS). The observations revealed that the cathode was effective in batteries assembled with materials associated with NaY and MCM-41. However, the battery assembled with HCM associated with zeolite 13X showed significantly lower, almost negligible, performance. The novel material exhibited characteristics of graphene fluoride. This finding confirms two key points, i) the reaction conditions involving hydrofluoric acid treatment facilitate the formation of graphene fluoride. and ii) the material is completely insulating, as indicated by the cathode's performance. These two applications in the field of gas adsorption and ionic conduction serve as a promising first step towards discovering other uses for porous materials with these characteristics in material sciences.