A Simple Descriptor toward Optimizing Electrocatalytic N₂ Oxidation to HNO₃ Performance over Graphene-Based Single-Atom Catalysts

Single-atom catalysts (SACs) exhibit tremendous advantages in the electrochemical N₂ oxidation reaction (EN₂OR) to HNO₃, which is an eco-friendly alternative to the synthesis of conventional industrial nitric acid and nitrates, but methods to rationally design and rapidly screen high-efficiency EN₂OR SACs are unclear. Herein, taking pyridinic nitrogen-doped graphene-supported SACs as an example, a simple descriptor has been proposed to evaluate the EN₂OR performance through systematically constructing a surface reaction phase diagram. This descriptor is comprised of merely the geometric information and inherent atomic properties (occupied d electron number, electronegativity, and coordinate number) that can accurately predict the activity and selectivity of EN₂OR, independent of DFT simulations. Based on this descriptor, high-throughput screening has been executed on partially N/C/O coordinated SACs, including 160 candidates; 13 candidates with the overpotential of less than 1.0 V are selected and then validated by DFT calculations with a mean absolute error (MAE) as low as 0.09 V, indicating the reliability of the descriptor. Meanwhile, the screened CoO₂N₂-G and RhO₂N₂-G SACs exhibit lower EN₂OR overpotential of 0.64 and 0.68 V and more negative <i>U</i>_L(EN₂OR) - <i>U</i>_L(OER) values of -0.34 and -0.44 V in comparison to other candidates, respectively, demonstrating the excellent activity and selectivity of EN₂OR. This work offers a route to rapid discovery of high-performance SACs for EN₂OR.