State Key Laboratory of Catalysis, CAS Center for Excellence in Nanoscience, Collaborative Innovation Center of Chemistry for Energy Materials, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Zhongshan Road 457, Dalian 116023, China.
University of Chinese Academy of Sciences, Beijing 100049, China.
Nat Commun. 2017 Feb 22;8:14459. doi: 10.1038/ncomms14459.
A major challenge limiting the practical applications of nanomaterials is that the activities of nanostructures (NSs) increase with reduced size, often sacrificing their stability in the chemical environment. Under oxidative conditions, NSs with smaller sizes and higher defect densities are commonly expected to oxidize more easily, since high-concentration defects can facilitate oxidation by enhancing the reactivity with O and providing a fast channel for oxygen incorporation. Here, using FeO NSs as an example, we show to the contrary, that reducing the size of active NSs can drastically increase their oxidation resistance. A maximum oxidation resistance is found for FeO NSs with dimensions below 3.2 nm. Rather than being determined by the structure or electronic properties of active sites, the enhanced oxidation resistance originates from the size-dependent structural dynamics of FeO NSs in O. We find this dynamic size effect to govern the chemical properties of active NSs.
限制纳米材料实际应用的一个主要挑战是，纳米结构（NSs）的活性随着尺寸的减小而增加，这往往牺牲了它们在化学环境中的稳定性。在氧化条件下，尺寸较小且缺陷密度较高的 NSs 通常更容易氧化，因为高浓度的缺陷可以通过增强与 O 的反应性并为氧的掺入提供快速通道来促进氧化。在这里，我们以 FeO NSs 为例，相反地表明，减小活性 NSs 的尺寸可以极大地提高它们的抗氧化性。在尺寸低于 3.2nm 时，FeO NSs 表现出最大的抗氧化性。增强的抗氧化性不是由活性位点的结构或电子性质决定的，而是源于 FeO NSs 在 O 中尺寸相关的结构动力学。我们发现这种动态尺寸效应控制着活性 NSs 的化学性质。
