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Resumo(s)
Diatomic catalysts, particularly those with heteronuclear active sites,
have recently attracted considerable attention for their advantages over single-atom
catalysts in reactions involving multielectron transfers. Herein, we report bimetallic
iridium−iron diatomic catalysts (IrFe−N−C) derived from metal−organic frameworks
in a facile wet chemical synthesis followed by postpyrolysis. We use various advanced
characterization techniques to comprehensively confirm the atomic dispersion of Ir and
Fe on the nitrogen-doped carbon support and the presence of atomic pairs. The asobtained
IrFe−N−C shows substantially higher electrocatalytic performance for both
oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) when
compared to the single-atom counterparts (i.e., Ir−N−C and Fe−N−C), revealing
favorable bifunctionality. Consequently, IrFe−N−C is used as an air cathode in zinc−
air batteries, which display much better performance than the batteries containing
commercial Pt/C + RuO2 benchmark catalysts. Our synchrotron-based X-ray
absorption spectroscopy experiments and density functional theory (DFT) calculations suggest that the IrFe dual atoms
presumably exist in an IrFeN6 configuration where both Ir and Fe coordinates with four N atoms and two N atoms are shared by the
IrN4 and FeN4 moieties. Furthermore, the Fe site contributes mainly to the ORR, while the Ir site plays a more important role in the
OER. The dual-atom sites work synergistically, reducing the energy barrier of the rate-determining step and eventually boosting the
reversible oxygen electrocatalysis. The IrFe−N−C catalysts hold great potential for use in various electrochemical energy storage and
conversion devices.
Descrição
Palavras-chave
Atomically dispersed catalyst IrFe diatomic active site Oxygen electrocatalysis Oxygen reduction reaction Oxygen evolution reaction