Size-dependent dynamic structures of supported gold nanoparticles in CO oxidation reaction condition
Size-dependent dynamic structures of supported gold nanoparticles in CO oxidation reaction condition
复制标题
CO氧化反应条件下负载金纳米颗粒的尺寸依赖性动态结构
DOI：
10.1073/pnas.1800262115
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发表时间：
2018-07-24
影响因子：
11.1
通讯作者：
Wang, Chongmin
中科院分区：
文献类型：
--
作者：
He, Yang;Liu, Jin-Cheng;Wang, Chongmin
黄金是最高贵的金属。然而，当尺寸减小到纳米级并负载在可还原的氧化物上时，即使在低温下，金纳米颗粒也显示出异常高的催化性能。在这里，通过最先进的原位像差校正环境透射电子显微镜和从头算分子动力学模拟，我们发现，在暴露于反应气体（一氧化碳和氧气）时，氧化铈上的超小金簇显示出尺寸依赖的有序到无序的转变，并产生动态的低配位原子，这可能可以有效地促进一氧化碳的氧化反应。研究结果提供了急需的见解的起源的大小依赖的催化性能的支持金，并证明了尺寸效应的颗粒相互作用，可能广泛存在，并在非均相催化剂中发挥重要作用。金（Au）催化剂表现出显著的尺寸效应，但其成因一直令人困惑。一般认为负载型Au团簇在工作条件下具有一定的刚性，这就不可避免地导致了人们普遍猜测其活性位是固定的。本文利用原子分辨率原位环境透射电子显微镜，研究了室温下氧化铈（CeO2）上单个Au纳米粒子在CO氧化反应条件下的尺寸依赖结构动力学。当大的Au纳米粒子在催化条件下保持刚性时，超小的Au团簇失去其固有结构并变得无序，具有剧烈的结构重排和表面动态低配位原子的形成。从头算分子动力学模拟表明，超小Au团簇与CO分子的相互作用导致了动态结构响应，表明催化剂颗粒在工作条件下的形状可能完全不同于静态条件下的形状.目前的观察提供了洞察超小金团簇的上级催化性能的起源。
Significance Gold is the noblest metal. However, when the size decreases to nanoscale and is supported on reducible oxides, the gold nanoparticle shows exceptionally high catalytic performance even at low temperatures. Here, through state-of-the-art in situ aberration-corrected environmental transmission electron microscopy and ab initio molecular-dynamic simulations, we discovered that, upon exposing to reactant gas (carbon monoxide and oxygen), ultrasmall gold clusters on ceria show a size-dependent order-to-disorder transformation with generation of dynamic low-coordinated atoms, which presumably can effectively boost the oxidation reaction of carbon monoxide. The findings provide much-needed insights on the origin of size-dependent catalytic properties of supported gold and demonstrate a size effect in absorbent–particle interactions that may widely exist and play an essential role in heterogeneous catalysts. Gold (Au) catalysts exhibit a significant size effect, but its origin has been puzzling for a long time. It is generally believed that supported Au clusters are more or less rigid in working condition, which inevitably leads to the general speculation that the active sites are immobile. Here, by using atomic resolution in situ environmental transmission electron microscopy, we report size-dependent structure dynamics of single Au nanoparticles on ceria (CeO2) in CO oxidation reaction condition at room temperature. While large Au nanoparticles remain rigid in the catalytic working condition, ultrasmall Au clusters lose their intrinsic structures and become disordered, featuring vigorous structural rearrangements and formation of dynamic low-coordinated atoms on surface. Ab initio molecular-dynamics simulations reveal that the interaction between ultrasmall Au cluster and CO molecules leads to the dynamic structural responses, demonstrating that the shape of the catalytic particle under the working condition may totally differ from the shape under the static condition. The present observation provides insight on the origin of superior catalytic properties of ultrasmall gold clusters.