Identifying the active sites of catalysts under working conditions is crucial for precise understanding of reaction mechanisms and rational design of catalysts. However, the nature of active sites of bimetallic catalysts for CO oxidation is still a subject of debate. Herein, we employ in situ X-ray absorption and infrared spectroscopy to monitor the realistic structures of active centers in a bimetallic Pt−Co/Al 2 O 3 catalyst during CO oxidation. This catalyst brings 100% CO conversion at room temperature and 30-fold higher turnover frequency than monometallic Pt/Al 2 O 3 catalysts. The in situ studies reveal that under the CO oxidation condition, a fraction of Co atoms are segregated from the PtCo alloy into the surface CoO species that decorates the remaining PtCo nanoparticles through direct Pt−O−Co interfacial bonds. The bond-valence analysis unravels one dangling Co−O coordination per Co 2+ in the surface CoO, which acts as the active sites for O 2 activation. The synergy between the CoO species and the PtCo alloy brings the superior catalytic activity. We also show that the directly connected Pt−O−Co interface is more beneficial to the catalytic performance than the unconnected Pt−CoO interface and provides a promising strategy toward the design of advanced catalysts for the redox reaction.
Semi-oxidized Co pre-catalysts are oxidized and self-assembled into defective CoOOH with a much higher O vacancy density during the OER, benefiting the bonding of oxygen species on the catalyst surface and promoting the catalytic activity.
Strong metal‐support interactions characteristic of the encapsulation of metal particles by oxide overlayers have been widely observed on large metal nanoparticles, but scarcely occur on small nanoclusters (<2 nm) for which the metal‐support interactions remain elusive. Herein, we study the structural evolution of Pt nanoclusters (1.5 nm) supported on anatase TiO2 upon high‐temperature H2 reduction. The Pt nanoclusters start to partially evolve into a CsCl‐type PtTi intermetallic compound when the reduction temperature reaches 400 °C. Upon 700 °C reduction, the PtTi nanoparticles are exclusively formed and grow epitaxially along the TiO2 (101) crystal faces. The thermodynamics of the formation of PtTi via migration of reduced Ti atoms into Pt cluster is unraveled by theoretical calculations. The thermally stable PtTi intermetallic compound, with single‐atom Pt isolated by Ti, exhibits enhanced catalytic activity and promoted catalytic durability for CO oxidation.
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