Catalytic performance of transition metal-doped M-NO/M-N₂O/M-N₄ systems for ORR and OER: A comprehensive study

To address the challenges related to energy and environmental concerns in fuel cells and metal-air batteries, electrochemical catalysis of oxygen reduction reactions (ORR) and oxygen evolution reactions (OER) offers a promising solution. In this study, the ORR/OER activities of transition metal-doped M-NO, M-N 2 O and M-N 4 complexes were systematically investigated using density functional theory and machine learning. The catalytic performances of 39 catalysts were examined for both ORR and OER. For ORR, Rh- and Ir-N 4 catalysts exhibit ultralow overpotentials of 0.26 and 0.30 V, respectively, matching or exceeding the activity of Pt(111). For OER, Co-N 4 shows excellent activity with an overpotential of 0.40 V, comparable to RuO 2 (110). Notably, Co-N 4 and Rh-N 4 demonstrate excellent bifunctional performance, with BI values of 0.90 and 0.73 V, respectively. The active site of M-N 4 has an appropriate adsorption behavior for the reaction species, which makes its activity superior to that of M-N 2 O and M-NO. The results of machine learning have shown that the M–O distance is identified as the most important feature, with an importance score of 44%. By analyzing the structure-activity relationships in M-N 4 systems, this work provides valuable insights for the rational design of advanced bifunctional electrocatalysts with improved ORR and OER activities. • DFT and ML analyze the bifunctional catalytic activity of M–NO, N₂O, and N₄. • M-N 4 exhibits enhanced stability and catalytic activity compared to N 2 O and NO. • Rh-N 4 possesses the lowest BI value with 0.73 V.