A review of NH3-SCR using nitrogen-doped carbon catalysts for NOx emission control

Abstract

This review evaluates the application of nitrogen-doped carbon (NDC) catalysts for mitigating nitrogen oxides (NO_x) emissions through selective catalytic reduction (SCR) using ammonia (NH₃). A key focus is exploring how the unique nitrogen functionalities of NDCs, such as pyridinic and graphitic nitrogen, enhance catalytic performance compared to traditional catalysts, providing deeper insight into their electronic structure and adsorption properties. This review emphasizes the advantages of NDC catalysts in stabilizing SCR reactions under demanding conditions and highlights recent advancements, such as improved synthesis techniques and the incorporation of transition metals to increase activity. Additionally, the review highlights breakthroughs in SCR technology, including the synergistic effects of metal incorporation into NDC structures and innovations in overcoming catalyst deactivation. Fundamental mechanisms of NO_x reduction are discussed, with an emphasis on the standard and fast SCR pathways and the interplay of Langmuir-Hinshelwood (L-H) and Eley-Rideal (E-R) mechanisms. The impact of synthesis methodologies, including templating and pyrolysis, on catalyst properties is also analyzed. Key performance factors, such as temperature and reactant concentrations, are examined, alongside strategies to enhance SCR performance by incorporating transition metals and ceria. Challenges like catalyst deactivation and stability are addressed, with potential solutions proposed. Finally, challenges like catalyst deactivation and stability are addressed, with proposed solutions, and future trends in NDC catalyst development to meet evolving emission regulations are outlined.