CARBON DIOXIDE ACTIVATION AND SUBSEQUENT REDUCTION TO VALUE-ADDED CHEMICALS AND FUELS ON GRAPHITIC CARBON NITRIDE SURFACES (UNCOMPRESSED VERSION)

Abstract

This doctoral thesis presents a comprehensive investigation into the synthesis, characterization, and photon-assisted catalytic performance of graphitic carbon nitride (g-C3N4) materials for carbon dioxide (CO2) reduction and water splitting. The research addresses the critical need for sustainable energy solutions and CO2 utilization in the face of global climate change. The study employs a multi-faceted approach, exploring various synthesis methods including one-pot, crucible-based, ionothermal, and supramolecular-assisted eutectic techniques. A wide array of advanced characterization methods, such as X-ray diffraction, spectroscopic techniques, and electron microscopy, are utilized to elucidate the structural, electronic, and surface properties of the synthesized materials. Novel analytical approaches, including derivative spectroscopy and machine learning algorithms, are introduced to enhance the understanding of structure property performance relationships. The research introduces innovative parameters, such as normalized surface concentration (NSC%) and light absorption efficiency per unit surface area (DP/SA), to provide deeper insights into photonassisted catalytic activity. The thesis is structured into two main sections, examining a total of 18 g-C3N4 systems. The first part investigates the impact of precursors and crucible materials on the photon-assisted catalytic performance of g-C3N4. The second part explores the synthesis of g-C3N4 derivatives using molecular salt- and supramolecularassisted pathways, including the iono thermal synthesis of lithium polytriazine imide (Li-PTI) and nickel-incorporated g-C3N4 frameworks. Key findings reveal the crucial role of surface functionalities, crystallinity, and electronic structure in determining the photon-assisted catalytic activity of g-C3N4 materials. The research demonstrates that factors such as synthesis atmosphere, precursor selection, and incorporation of metal ions significantly influence the CO2 reduction performance. The thesis concludes by proposing new design criteria for photon-assisted catalytic systems, emphasizing the importance of considering both catalyst characteristics and effective illumination. It highlights the need for a paradigm shift in approach, suggesting that the wavelength and intensity of incident photons should be tailored to the specific properties of the photon-assisted catalyst. This comprehensive study contributes to the fundamental understanding of g-C3N4 photon-assisted catalysts and provides valuable insights for the rational design of efficient materials for CO2 reduction and solar fuel production. The findings have significant implications for the development of sustainable energy technologies and environmental remediation strategies.