Abstract
A ternarycatalyst comprisingIridium(Ir) single-atoms(SA)s decorated on the Co-oxidesupported palladium(Pd) nanoparticles (denoted asCPI-SA) is developed in this work. TheCPI-SA with 1 wt.% of Ir exhibits unprecedented high massa ctivity (MA) of 7173 and 770mA mgIr−1, respectively, at 0.85 and 0.90V versus RHE in alkaline ORR (0.1m KOH), out performing the commercial Johnson Matthey Pt catalyst (J.M.-Pt/C; 20wt.% Pt) by 107-folds. More importantly, the high structural reliability of the Ir single-atoms endows the CPI-SA withoutstanding durability, where it shows progressively increasing MA of 13342 and 1372 mA mgIr−1, respectively, at 0.85 and 0.90V versus RHE up to 69000 cycles (3months) in the accelerated degradation test (ADT). Evidence from the insitu partial fluorescence yield X-rayabsorption spectroscopy (PFY-XAS) and the electrochemical analysis indicate that the Ir single-atoms and adjacent Pd domains synergistically promote the O2 splitting and subsequent desorptionof hydroxide ions(OH−), respectively. Whereas the Co-atoms underneath serve aselectron injectors to boost the ORR activity of the Irsingle-atoms. Besides, a progressive and sharp drop in the ORR performance is observed when Ir-clusters and Ir nanoparticles are decorated on the Co-oxide-supported Pd nanoparticles.