The role identification of nitrogen dopant in nanocarbon catalysis

The influence of nitrogen dopants on the catalytic activity of carbon-based materials has been a subject of extensive research, but the exact role of nitrogen species in these materials remains a topic of debate. One of the challenges in understanding the role of nitrogen is that most nitrogen-doped nanocarbons (NCs) materials are dominated by uncontrollable surface functional groups, and changes in nitrogen species often lead to variations in oxygen functional groups, making it difficult to isolate the specific role of nitrogen. To address this issue, we develop a series of new NCs with variable types and contents of nitrogen (ranging from approximately 5 to 30 at%), while keeping the oxygen content constant at around 4 at%. The study clarified that different types of nitrogen in the NCs, namely graphitic nitrogen and pyridinic nitrogen, serve as electron-donating and electron-withdrawing modulators, respectively, which can tailor the oxidative dehydrogenation (ODH) activity of the NCs. Additionally, the study found that graphitic nitrogen plays a role in mediating frustrated Lewis pairs, consisting of both pyridinic nitrogen and neighboring carbon atoms. These pairs are responsible for the activation of hydrogen-hydrogen bonds, considered as the rate-determining step in the nitrobenzene hydrogenation reaction.