Exploration of Lewis basicity and oxygen reduction reaction activity in plasma-tailored nitrogen-doped carbon electrocatalysts

The ORR electrocatalytic activity of nitrogen-doped carbon (N-doped carbon) is highly related to the type of nitrogen bondings, which is originated to the charge transfer between carbon and nitrogen. Based on Lewis theory of acid-base reactions, N-doped carbon can be defined as a Lewis base catalyst. The lone pair of electrons on the nitrogen atom mainly contributed to its reactivity, or in other terms, Lewis basicity. Herein, we fabricated selective amino-N, pyrrolic-N, nitrile-N, and oxide-N in N-doped carbon systematically, as well as compared their electrocatalytic activities and Lewis basicities for the first time. Based on the molecular structure of four starting precursors, aniline (C₆H₅NH₂), pyrrole (C₄H₅N), benzonitrile (C₅H₇N), and nitrobenzene (C₆H₅NO₂) were successfully formed as selective amino-N, pyrrolic-N, nitrile-N and oxide-N, respectively, via a room temperature plasma synthesis process. From the electrochemical performance, N-doped carbon catalyst with highly selective amino-N demonstrated comparatively higher ORR activity in terms of ORR onset potential and current density. Also, we confirmed the correlation between the ORR activity and Lewis basicity of various N moieties. Based on the electronic structural properties, amino-N with the most superior ORR activity also exhibited the highest basic strength among the studied C[sbnd]N bonding structure. This study provided the relationship among the structural properties, Lewis basicity, and electrocatalytic activity of selective N-doped carbon.