UC Irvine

Nitrate reduction reaction in an electrochemical system has recently supplied us with a new pathway to generate ammonia for a post-carbon world. However, the low current density and yield rate as shown in relevant studies limit the NO3RR process. In this thesis, we developed a new catalyst system consisting of γ-Fe2O3 nanoparticles supported on atomically dispersed Fe-N-C. By combining the activity of both the nanoparticles and single atom sites, we were able to achieve an ultrahigh NO3RR activity, with a maximum partial current density of 1.95 A/cm2, a Faradaic efficiency for NH3 of 100%, and an NH3 yield rate of over 9 mmol hr-1 cm-2. Our result of XPS after electrochemical experiments demonstrates the importance of a pre-reduction activation step to generate exposed Fe0 sites from the γ-Fe2O3 (Fe3+) and durability study reveals the robustness of the catalyst, maintaining a current of -1.4 A cm-2, a near unity FENH3 over 24 hours at highly reductive potentials. These findings highlight the potential of active particle-active support systems to enhance NO3RR performance and achieve industrially relevant current densities.