The restructuring of dilute alloys under gas environments has shown a great impact on their catalytic performance due to intriguing structural sensitivity, but the structural dynamics and underlying mechanism remains elusive. Herein, we directly resolved the distinct dynamic behaviors of PdFe_0.08 dilute alloys under CO or O₂ environment by multidimensional imaging. The stronger binding of gaseous CO with Fe atoms stimulates Fe segregation out of the PdFe_0.08, resulting in 3D growth of Fe islands, whereas the dissociative adsorption of O₂ results in 2D layer-by-layer growth of segregated FeO as encapsulation overlayers that bind strongly with the Pd surface underneath. Such varied structures remarkably tune the catalytic activity for CO oxidation, showing a considerably high activity for a CO-treated sample. Our results reveal the competitive mechanism between adsorbate-metal and metal–metal interaction for gas-induced surface segregation, which should be highly considered for the rational design of dilute alloys with dynamically tuned structure and reactivity.

中文翻译：

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多维成像揭示 PdFe0.08 稀合金气体诱导表面偏析的动力学和竞争机制


由于有趣的结构敏感性，稀合金在气体环境下的重组对其催化性能产生了很大影响，但结构动力学和潜在机制仍然难以捉摸。在此，我们通过多维成像直接解析了 PdFe_0.08 稀合金在 CO 或 O₂ 环境下的独特动力学行为。气态 CO 与 Fe 原子的更强结合刺激 Fe 从 PdFe_0.08 中分离出来，导致 Fe 岛的 3D 生长，而 O₂ 的解离吸附导致分离的 FeO 作为封装覆盖层的 2D 逐层生长，与下面的 Pd 表面紧密结合。这种不同的结构显著调节了 CO 氧化的催化活性，对 CO 处理样品显示出相当高的活性。我们的结果揭示了吸附物-金属和金属-金属相互作用之间导致气体诱导表面偏析的竞争机制，在合理设计具有动态调整结构和反应性的稀合金时，应高度考虑这一点。