Ab initio theoretical studies of electrocatalysis for oxygen and carbon dioxide reduction reactions

Abstract

The present PhD thesis focuses on the investigation of model catalysts, primarily Fe-N-C macrocycles, in two key electrochemical processes: the oxygen reduction reaction (ORR) and the carbon dioxide reduction reaction (CO2RR). Additionally, the nitrogen-doped carbon material in ORR is also studied. The main motivation behind this research is to lay the groundwork for the rational design of catalysts that can be effectively employed in electrochemical cells. Such catalysts have the potential to significantly mitigate CO2 emissions, contribute to the closure of the carbon cycle, and facilitate the utilisation of renewable energy sources. By employing DFT calculations, this thesis explores the electronic structures, binding energies, and thermodynamic considerations of the model catalysts. In the first project, the theoretical computations are combined with experimental data to comprehensively unravel the mechanisms of Fe-N-C macrocycles for the ORR. In the following project, the transition metal carbon M-N-C (M=Fe, Co, Ni, Cu) with the same macrocycle structures in the previous study are applied to screen for selective and efficient CO2RR catalyst. It turns out the Fe-N-C is also a promising CO2RR catalyst and further analysis is conducted. For the last project, the nitrogen doped carbon model catalysts are employed to understand a long-standing contentious issue: origin of their ORR active site. The insights gained from these studies shed light on the underlying mechanisms and key factors governing the catalytic performance of these materials. The research outcomes presented in this thesis contribute to the advancement of catalyst design strategies for the ORR and CO2RR, highlighting the potential for achieving sustainable energy conversion processes. The reduction of CO2 emissions and the establishment of a closed carbon cycle can be facilitated, promoting a greener and more sustainable future.