Luo Langli, Chen Shuyue, Xu Qian, He Yang, Dong Zejian, Zhang Lifeng, Zhu Junfa, Du Yingge, Yang Bo, Wang Chongmin
Institute of Molecular Plus, Tianjin Key Laboratory of Molecular Optoelectronic Sciences, Department of Chemistry , Tianjin University , 92 Weijin Road , Tianjin 300072 , China.
School of Physical Science and Technology , Shanghai Tech University , 393 Middle Huaxia Road , Shanghai 201210 , China.
J Am Chem Soc. 2020 Feb 26;142(8):4022-4027. doi: 10.1021/jacs.9b13901. Epub 2020 Feb 14.
Supported alloy nanoparticles are prevailing alternative low-cost catalysts for both heterogeneous and electrochemical catalytic processes. Gas molecules selectively interacting with one metal element induces a dynamic structural change of alloy nanoparticles under reaction conditions and largely controls their catalytic properties. However, such a multicomponent dynamic-interaction-controlled evolution, both structural and chemical, remains far from clear. Herein, by using state-of-the-art environmental TEM, we directly visualize, at the atomic scale, the evolution of a AuCu alloy nanoparticle supported on CeO during CO oxidation. We find that gas molecules can "free" metal atoms on the (010) surface and form highly mobile atom clusters. Remarkably, we discover that CO exposure induces Au segregation and activation on the nanoparticle surface, while O exposure leads to the segregation and oxidation of Cu on the particle surface. The as-formed CuO/AuCu interface may facilitate CO-O interaction corroborated by DFT calculations. These findings provide insights into the atomistic mechanisms on alloy nanoparticles during catalytic CO oxidation reaction and to a broad scope of rational design of alloy nanoparticle catalysts.
负载型合金纳米颗粒是用于多相催化和电化学催化过程的主流低成本替代催化剂。在反应条件下，与一种金属元素选择性相互作用的气体分子会引起合金纳米颗粒的动态结构变化，并在很大程度上控制其催化性能。然而，这种结构和化学上的多组分动态相互作用控制的演化仍远未明确。在此，通过使用最先进的环境透射电子显微镜，我们在原子尺度上直接观察到了负载在CeO上的AuCu合金纳米颗粒在CO氧化过程中的演化。我们发现气体分子可以使（010）表面上的金属原子“游离”出来并形成高度可移动的原子团簇。值得注意的是，我们发现CO暴露会导致纳米颗粒表面的Au偏析和活化，而O暴露会导致颗粒表面的Cu偏析和氧化。形成的CuO/AuCu界面可能会促进CO-O相互作用，这得到了密度泛函理论计算的证实。这些发现为催化CO氧化反应过程中合金纳米颗粒的原子机制提供了见解，并为合金纳米颗粒催化剂的广泛合理设计提供了依据。
