Abstract
The hybridization of single atom sites (SASs) and nanoparticles (NPs) demonstrates enhanced stability under acidic electrochemical environments when compared to their individual components; however, the underlying synergistic mechanisms remain elusive. Here we synthesize a hybrid catalyst featuring electron transfer from Pt(3)Fe NPs to high-spin D1-type FeN(4) SASs. The online inductively coupled plasma mass spectrometry technique confirms a mutual suppression of electrochemical dissolution between Pt(3)Fe and D1-FeN(4). In situ spectroscopy and theoretical calculations elucidate the mechanisms at play: electron enrichment at the D1-FeN(4) site strengthens the Fe-N bond, thereby elevating the N-hydrogenation energy barrier. Conversely, electron withdrawal reduces the d-band center of Pt, consequently weakening the oxygen adsorption strength and inhibiting the formation of Pt oxides. Owing to mutual dissolution inhibition, the hybrid catalyst retains 99.6% of its oxygen reduction reaction (ORR) mass activity at 0.85 V (versus RHE) following 30,000 accelerated stress test cycles between 0.6 and 1.0 V in an inert atmosphere, markedly surpassing those of single-component counterparts. This work offers critical insights into the intricate synergistic interactions between SASs and NPs, paving the way for the rational design of SASs-NPs hybrid catalysts for ORR or beyond.