气氛环境下Au/CeO_(2)催化剂烧结行为的原位电镜研究

In⁃situ TEM study of gas⁃dependent sintering behavior of Au/CeO_(2)

气氛环境下原位研究催化剂的烧结行为,能够为理解催化剂在预处理以及反应条件下的烧结机理和高稳定催化剂的设计提供重要的实验依据。本文以Au/CeO_(2)模型纳米催化剂为研究对象,利用环境透射电子显微镜原位观察其在O_(2)与CO气氛下的高温动态烧结过程。实验发现,负载在CeO_(2)上的Au纳米颗粒在O_(2)与CO气氛环境中表现出不同的烧结行为,其在O_(2)气氛下具有较高的烧结速度,同时存在颗粒迁移与聚集长大(particle migration and coalescence,PMC)和奥斯特瓦尔德熟化(Ostwald ripening,OR)两种烧结过程;在CO气氛下烧结速度较慢,烧结过程以OR为主。对比不同气氛环境下烧结后催化剂的表面结构可知,CO增加了CeO_(2)表面台阶的数量以及表面氧空位浓度,增强了载体对Au颗粒的锚定作用,从而提升Au/CeO_(2)催化剂的稳定性。

In⁃situ investigation of catalyst sintering behavior under atmospheric conditions provides the crucial experimental evidence for understanding the sintering mechanism of catalysts during pretreatments and reactions,and for designing highly stable catalysts.In this study,a model nanocatalyst system composed of Au/CeO_(2)was employed to examine the high⁃temperature dynamic sintering process using an environmental transmission electron microscopy(ETEM).It was observed that the Au nanoparticles supported on CeO_(2)exhibited distinct sintering behaviors in O_(2)and CO atmospheres.In the O_(2)atmosphere,the sintering rate was significantly accelerated by the presence of both particle migration and coalescence(PMC)and Ostwald ripening(OR)processes.In contrast,in the CO atmosphere,the sintering rate was slow and predominantly governed by the OR process.The comparative analysis of the surface structures of sintered catalysts under different atmospheres revealed that the CO gas increased the number of surface steps and the concentration of surface oxygen vacancies in CeO_(2),thereby enhancing the anchoring effect of the support on Au particles,and improving the stability of the Au/CeO_(2)catalyst.