Multi-function core-shell nanoparticles outperform single-phase counterparts for efficient single-atom catalysis

Nanoparticles (NPs) have been shown to enhance single-atom catalysis (SAC). However, current NPs are limited to single-phase and only display limited function and efficiency. Employing operando spectra, kinetic isotope effect, local pH measurement, and density functional theory calculations, we reveal that the core-shell Fe@Fe 3 O 4 NPs, as a whole, realize weakening *OH adsorption, promoting water dissociation, and tandem proton transfer. This enables Fe SAs -Fe@Fe 3 O 4-NPs to achieve an ORR half-wave potential ( E 1/2 ) of 0.952 V vs. reversible hydrogen electrode (V RHE ), outperforming commercial Pt/C ( E 1/2 = 0.844 V RHE ) and the Fe SAs -Fe NPs ( E 1/2 = 0.919 V RHE ). More importantly, the Fe 3 O 4 shell protecting the Fe core provides robust durability with negligible loss after 50,000 potential cycles between 0.6 and 1.0 V RHE , distinct from partial oxidation of Fe NPs under the oxygen reduction reaction conditions. At a device level, zinc-air batteries with Fe SAs -Fe@Fe 3 O 4-NPs as cathodic catalysts realize a peak power density of 250.2 mW cm −2 and stable operation > 10,000 charge-discharge cycles with RuO 2 at 10 mA cm −2 . This work implies a new room to enhance the SAC and offers comprehensive insights into understanding NPs in steering reaction kinetics. Download: Download high-res image (154KB) Download: Download full-size image