Author(s):
Yu, Zhipeng ; Si, Chaowei ; LaGrow, Alec P. ; Tai, Zhixin ; Caliebe, Wolfgang A. ; Tayal, Akhil ; Sampaio, Maria J. ; Sousa, Juliana P. S. ; Amorim, Isilda ; Araujo, Ana ; Meng, Lijian ; Faria, Joaquim L. ; Xu, Junyuan ; Li, Bo ; Liu, Lifeng
Date: 2022
Persistent ID: http://hdl.handle.net/10400.22/20798
Origin: Repositório Científico do Instituto Politécnico do Porto
Subject(s): Atomically dispersed catalyst; IrFe diatomic active site; Oxygen electrocatalysis; Oxygen reduction reaction; Oxygen evolution reaction
Description
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.
