High-density asymmetric iron dual-atom sites for efficient and stable electrochemical water oxidation.

Double-atom catalysts (DACs) have opened distinctive paradigms in the field of rapidly developing atomic catalysis owing to their great potential for promoting catalytic performance in various reaction systems. However, increasing the loading and extending the service life of metal active centres represents a considerable challenge for the efficient utilization of DACs. Here, we rationally design asymmetric nitrogen, sulfur-coordinated diatomic iron centres on highly defective nitrogen-doped carbon nanosheets (denoted A-FeSN/SNC, A: asymmetric), which possess the atomic configuration of the NSFe-FeN moiety. The abundant defects and low-electronegativity heteroatoms in the carbon-based framework endow A-FeSN/SNC with a high loading of 6.72 wt%. Furthermore, A-FeSN/SNC has a low overpotential of 193 mV for the oxygen evolution reaction (OER) at 10 mA cm, outperforming commercial RuO catalysts. In addition, A-FeSN/SNC exhibits extraordinary stability, maintaining > 97% activity for over 2000 hours during the OER process. This work provides a practical scheme for simultaneously balancing the activity and stability of DACs towards electrocatalysis applications.