Tailoring Native and Transition Metal Catalytic Sites in Graphitic Carbon Nitride for Sustainable Material Design

Abstract

Graphitic carbon nitride (g-C3N4) has emerged as a promising material for sustainable energy conversion applications due to its unique electronic structure, earth-abundant composition, and facile synthesis. However, its practical implementation is hindered by limitations in charge separation and catalytic activity. This thesis presents a comprehensive investigation into tailoring g-CN through advanced synthesis, exfoliation, and metal doping strategies, with a focus on enhancing its performance in air-metal batteries and photoelectrochemical systems.

A novel femtosecond laser irradiation technique for g-C3N4 exfoliation is introduced, demonstrating superior control over layer thickness and defect density compared to conventional methods. The exfoliation process is optimized to yield exfoliated g-C3N4 nanosheets with tunable bandgaps and increased active surface area.

Subsequently, a systematic study of metal doping (Cu, Fe, Ni, Co) on exfoliated g-C3N4 is conducted. The influence of dopant type, concentration, and incorporation method on the material's electronic structure and catalytic properties is elucidated through experimental characterization. Particular emphasis is placed on correlating the metal-nitrogen coordination environments with observed enhancements in charge transfer and oxygen reduction/evolution kinetics.

The tailored M-g-C3N4 materials are then evaluated in air-metal battery and photoelectrochemical cell configurations. Viable improvements in battery capacity, cycle life, and conversion efficiency are demonstrated relative to undoped g-C3N4 and benchmark catalysts. Mechanistic insights into the enhanced performance are provided through in-situ spectroscopic studies and post-operation material characterization.

Finally, the environmental impact and scalability of the developed materials and processes are assessed, providing a holistic perspective on their potential for real-world implementation in green catalysis and energy storage applications.

This work establishes design principles for optimizing g-C3N4-based materials and demonstrates their promise as sustainable alternatives to precious metal catalysts in next-generation energy conversion devices.