Electronic Properties of Metal-/Nitrogen-Doped Graphene Single Atom Catalysts from First Principles

Metal-/nitrogen-doped graphene catalysts (MNCs) are a promising class of materials for electrochemical energy conversion, owing to their ability to drive HER and ORR, though their rational design is hindered by the structural heterogeneity produced during synthesis. While traditional computational screening relies on static binding energies, this work utilizes grand-canonical density functional theory (GC-DFT) to rigorously model the potential-dependent electrochemical interface of 232 distinct MNC models. We systematically varied the transition metal center, the number of coordinating nitrogen atoms (MNxGr, x = 1–4), and the local coordination geometry (pyridinic vs pyrrolic) to map out fundamental thermodynamic and electronic properties. Our results reveal a key dichotomy between the coordination geometries: pyridinic sites are consistently more thermodynamically stable, whereas pyrrolic sites exhibit significantly higher interfacial capacitance, indicative of a greater density of states near the Fermi level. Crucially, we demonstrate that thermodynamic stability, as measured by the formation energy, is largely decoupled from key electronic properties like the potential of zero charge (PZC) and capacitance, suggesting these interfacial electrostatic properties can be tuned independently. Furthermore, a Boltzmann analysis demonstrates that higher synthesis temperatures make less stable, under-coordinated structures thermodynamically accessible, providing a theoretical basis for the observed heterogeneity in pyrolyzed materials. This work establishes a foundational map to guide the future rational design of MNCs with tailored functionalities.