Heteroatom-doped carbon materials have emerged as sustainable, earth-abundant catalysts. Among them, pyrolytically synthesized nitrogen-doped carbons are the most common type, where N atoms are incorporated into carbon primarily as pyridinic, pyrrolic, and graphitic types. It has been observed that the doping of the carbon surface with N atoms enhances the electrochemical activity of the catalyst. However, traditional pyrolysis conditions result in uncontrolled mixtures of N functionalities which has limited the design of catalysts optimized for electrocatalytic applications. Moreover, developing structure–activity relationships in N-doped carbons is complicated by the coexistence of random N configurations and by changes in the material’s physical properties induced by pyrolysis. In this work, we systematically investigate the thermodynamic and kinetic transformations that govern the pyrolytic evolution of N functionalities. Using a controlled model platform, N-containing precursor molecules with a specified N functionality were adsorbed onto carbon black through vapor deposition and subject to pyrolysis. This approach selectively modifies the surface of the carbon while preserving its physical structure, enabling direct study of N functionality transformations. We show that the thermodynamically favored state of all systems is where all three of the N functionalities coexist as a mixture, independent of the precursor molecule starting functionality. Furthermore, we demonstrate that kinetic stabilization enables functionalization of carbon with 100% specified N configurations. Using these isolated N-functionalized materials, we were able to measure the intrinsic activity of each N type for the CO₂ electrochemical reduction, determining that pyrrolic N exhibits the highest activity, followed by pyridinic and graphitic. Collectively, these findings clarify the fundamental insight of N incorporation during pyrolysis that determines the resulting N functionality distribution. Beyond advancing fundamental understanding, this work provides a foundation for the precision design of N-doped carbon materials for various applications in electrochemical energy conversion technologies.
