Mesopore carbon spheres anchored atomic Fe catalysis enables high performance oxygen reduction and ultralong-life rechargeable Zn-air batteries

Single atom catalysts (SACs) featuring Fe-N₄ active sites anchored on carbon supports exhibit exceptional electrocatalytic performance in oxygen reduction reactions (ORR). Herein, a rigid ligand confined strategy was used to synthesize edge-anchored Fe-N₄ active sites with geometric distortion on mesoporous-dominated carbon spheres (Fe-N-MESs). Furthermore, in situ Fourier transform infrared spectroscopy (FTIR) demonstrates that Fe-N-MESs weaken the O–O band, inhibiting the formation of H₂O₂. The density functional theory (DFT) calculations reveal that the exceptional ORR activity stems from optimized oxygen intermediate adsorption free energy and reduced OH^* desorption energy barrier. Electrochemical measurements verify the remarkable ORR activity of Fe-N-MESs, demonstrating a half-wave potential of 0.90 V and excellent stability, with approximately 94% of the initial current density after 50 h of operation. When used as the air cathode in aqueous Zn-air batteries, Fe-N-MESs display a large open circuit voltage of 1.53 V and an extra-long stability of 1500 h. Moreover, Fe-N-MESs exhibit a remarkable open circuit voltage of 1.50 V and an impressive peak power density up to 260.4 mW·cm⁻² in quasi-solid-state Zn-air batteries. This work provides valuable insights into the boosted ORR origin, while offering a novel and economical synthesis technique for SACs applicable to other electrocatalytic reactions.