Atomic Resolution Observation of a Size-Dependent Change in the Ripening Modes of Mass-Selected Au Nanoclusters Involved in CO Oxidation

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• 作者：Kuo-Juei Hu ; Simon R. Plant ; Peter R. Ellis ; Christopher M. Brown ; Peter T. Bishop ; Richard E. Palmer
• 刊名：Journal of the American Chemical Society
• 出版年：2015
• 出版时间：December 9, 2015
• 年：2015
• 卷：137
• 期：48
• 页码：15161-15168
• 全文大小：605K
• ISSN：1520-5126

文摘

Identifying the ripening modes of supported metal nanoparticles used in heterogeneous catalysis can provide important insights into the mechanisms that lead to sintering. We report the observation of a crossover from Smoluchowski to Ostwald ripening, under realistic reaction conditions, for monomodal populations of precisely defined gold particles in the nanometer size range, as a function of decreasing particle size. We study the effects of the CO oxidation reaction on the size distributions and atomic structures of mass-selected Au_561卤13, Au_923卤20 and Au_2057卤45 clusters supported on amorphous carbon films. Under the same conditions, Au_561卤13 and Au_923卤20 clusters are found to exhibit Ostwald ripening, whereas Au_2057卤45 ripens through cluster diffusion and coalescence only (Smoluchowski ripening). The Ostwald ripening is not activated by thermal annealing or heating in O₂ alone.