Also, the moderate EMSI of CeO2-supported Rh subnanoclusters furthest benefited activation of the adsorbed CO molecule and ensured it the highest activity among CeO2-supported Ru, Rh, and Ir catalysts with similar metal deposit sizes. According to the results of multiple ex situ and in situ characterizations, the much different activities of Ru, Rh, Ir, and Pd were derived from the alterable electronic metal–support interactions (EMSI), which determine the concurrent reaction pathway including the famous Mars van Krevelen mechanism and carbonate–intermediate route on the most active metal sites of Mδ+ (0 < δ < 1) for Ru, Rh, and Ir and Pd2+ for Pd. The subnanoclusters and nanoparticles of Ru, Rh, and Ir showed much higher activities than those of the single atoms, while a Pd single-atom catalyst was more active than Pd subnanoclusters and nanoparticles. In this work, we report the catalytic performances of CeO2-supported noble-metal catalysts among single atoms, subnanoclusters (∼1 nm), and nanoparticles (2.2–2.7 nm) upon low-temperature CO oxidation reaction between 50 and 250 ☌. Finally, the influence of speciation of the precursor on reduction kinetics is highlighted, followed by our perspectives on the challenges and future endeavors in achieving a controllable and predictable synthesis of noble-metal nanocrystals.Ī fundamental study on the metal–support interactions of supported metal catalysts is of great importance for developing heterogeneous catalysts with high performance, is still attracting and challenging in many heterogeneous catalytic reactions.
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We then illustrate how to extend the strategy into a bimetallic system for the preparation of nanocrystals with different shapes and elemental distributions. The kinetic approaches for controlling both nucleation and growth in a one-pot setting are then introduced with an emphasis on manipulation of the reduction pathways taken by the precursor. With a focus on Pd nanocrystals, we first offer a discussion on the correlation between the initial reduction rate and the internal structure of the resultant seeds. Here we present a brief Viewpoint on the recent progress in leveraging reduction kinetics for controlling and predicting the outcome of a synthesis of noble-metal nanocrystals.
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Different from a conventional trial-and-error approach, the reduction kinetics of a colloidal synthesis has recently been demonstrated as a reliable knob for controlling the synthesis of noble-metal nanocrystals in a deterministic and predictable manner. Improving the performance of noble-metal nanocrystals in various applications critically depends on our ability to manipulate their synthesis in a rational, robust, and controllable fashion.