Surface-supported isolated atoms in single-atom catalysts (SACs) are usually stabilized by diverse defects. The fabrication of high-metal-loading and thermally stable SACs remains a formidable challenge due to the difficulty of creating high densities of underpinning stable defects. Here we report that isolated Pt atoms can be stabilized through a strong covalent metal-support interaction (CMSI) that is not associated with support defects, yielding a high-loading and thermally stable SAC by trapping either the already deposited Pt atoms or the PtO2 units vaporized from nanoparticles during high-temperature calcination. Experimental and computational modeling studies reveal that iron oxide reducibility is crucial to anchor isolated Pt atoms. The resulting high concentrations of single atoms enable specific activities far exceeding those of conventional nanoparticle catalysts. This non defect-stabilization strategy can be extended to non-reducible supports by simply doping with iron oxide, thus paving a new way for constructing high-loading SACs for diverse industrially important catalytic reactions.
Metal
atoms dispersed on the oxide supports constitute a large
category of single-atom catalysts. In this review, oxide supported
single-atom catalysts are discussed about their synthetic procedures,
characterizations, and reaction mechanism in thermocatalysis, such
as water–gas shift reaction, selective oxidation/hydrogenation,
and coupling reactions. Some typical oxide materials, including ferric
oxide, cerium oxide, titanium dioxide, aluminum oxide, and so on,
are intentionally mentioned for the unique roles as supports in anchoring
metal atoms and taking part in the catalytic reactions. The interactions
between metal atoms and oxide supports are summarized to give a picture
on how to stabilize the atomic metal centers, and rationally tune
the geometric structures and electronic states of single atoms. Furthermore,
several directions in fabricating single-atom catalysts with improved
performance are proposed on the basis of state-of-the-art understanding
in metal-oxide interactions.
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