美国加州大学洛杉矶分校Anastassia N. Alexandrova课题组近日取得一项新成果。经过不懈努力，他们发现当流动性胜过尺寸选择时，亚纳米团簇的Ostwald成熟会加速。 相关论文于2021年3月2日发表于国际顶尖学术期刊《德国应用化学》上。

据介绍，尺寸选择已被证明可抑制负载型催化纳米颗粒的奥斯特瓦尔德成熟。课题组人员表明，当所负载的簇形物尺寸是亚纳米级且具有高通量时，例如金红石TiO₂（110）表面上的Pt簇形物，这个范例被破坏，已经建立的烧结理论需要更正。

在具有催化特性的温度下(即约700 K）的亚纳米簇热填充了许多低能的亚稳态异构体。由于这些异构体都具有不同的几何和电子结构，因此形成能和解离能（代替表面能），尽管选择了大小，但奥斯特瓦尔德熟化并未受到抑制。

但是，就整体烧结稳定性而言，有些簇形物以魔术数的形式出现。在多分散体系中，亚稳物质的烧结加速作用虽然减弱，但仍然存在。最后，该课题组提出了一种竞争性烧结途径理论，该理论在原子水平上描述了所发现的特定尺寸的烧结行为。

附：英文原文

Title: When Fluxionality Beats Size Selection:  Acceleration of Ostwald Ripening of Sub‐Nano Clusters

Author: Borna Zandkarimi, Patricia Poths, Anastassia N. Alexandrova

Issue&Volume: 2021-03-02

Abstract: Size selection was demonstrated to suppress Ostwald ripening of supported catalytic nanoparticles. We show here that when the supported clusters are sub‐nanometer in size and highly fluxional, such as Pt clusters on the rutile TiO  2  (110) surface, this paradigm breaks down, and the established theory of sintering needs a revision. At temperatures characteristic of catalysis (i.e. 700 K), sub‐nano clusters thermally populate many low‐energy metastable isomers. As these isomers all have different geometric and electronic structures, and thus, formation and dissociation energies (in lieu of surface energy), Ostwald ripening is not suppressed, despite the size‐selection. However, some clusters arise as magic numbers in terms of sintering stability at the ensemble level. The acceleration of sintering by metastable species persists though weakens in polydisperse cluster systems. Lastly, we propose a competing pathways theory for sintering, which at the atomistic level, describes the found size‐specific sintering behavior.

DOI: 10.1002/anie.202100107

Source: https://onlinelibrary.wiley.com/doi/10.1002/anie.202100107