Pyrrole-type TM-N3 sites as high-efficient bifunctional oxygen reactions electrocatalysts: From theoretical prediction to experimental validation

Employing density functional theory calculations combined with experimental studies, the structure-activity relationships and potential of pyrrole-type transition metal-N 3 (TM-po-N 3 ) as oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) bifunctional catalysts were systematically explored. Efficient catalysis of the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is essential for the rechargeable zinc-air batteries (R-ZABs). However, challenges remain due to the scarcity of effective bifunctional electrocatalysts and limited understanding of the structure-activity relationships. Pyrrole-type single-atom catalysts (SACs) with unique electronic structures have emerged as promising electrocatalysts. In this work, we combine density functional theory (DFT) calculations and experimental studies to systematically explore the structure-activity relationships and potential of pyrrole-type transition metal-N 3 (TM-po-N 3 ) as bifunctional catalysts. DFT calculations reveal that differences in the dependence of ORR and OER activities on the free energy of adsorption of reaction intermediates significantly affect the TM-po-N 3 bifunctional activity and identify magnetic Cu-po-N 3 as the best candidate. The bifunctional activity of Cu-po-N 3 originates from interactions between spin-polarized out-of-plane Cu_3 d and O_2 s +2 p orbitals. Theoretical predictions are validated experimentally, showing that the synthesized Cu-SAC/NC exhibits excellent bifunctional performance with a small potential gap of 0.666 V. Additionally, the assembled R-ZABs display a high-power density of 170 mW cm −2 and long-term stability, with the charge-discharge voltage gap increasing by only 0.01 V over 240 h. This work provides new insights into the design of efficient bifunctional catalysts.