Li Rongtan, Xu Xiaoyan, Zhu Beien, Li Xiao-Yan, Ning Yanxiao, Mu Rentao, Du Pengfei, Li Mengwei, Wang Huike, Liang Jiajie, Chen Yongsheng, Gao Yi, Yang Bing, Fu Qiang, Bao Xinhe
State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, The Chinese Academy of Sciences, Dalian, China.
University of Chinese Academy of Sciences, Beijing, China.
Nat Commun. 2021 Mar 3;12(1):1406. doi: 10.1038/s41467-021-21552-2.
Oxidative dispersion has been widely used in regeneration of sintered metal catalysts and fabrication of single atom catalysts, which is attributed to an oxidation-induced dispersion mechanism. However, the interplay of gas-metal-support interaction in the dispersion processes, especially the gas-metal interaction has not been well illustrated. Here, we show dynamic dispersion of silver nanostructures on silicon nitride surface under reducing/oxidizing conditions and during carbon monoxide oxidation reaction. Utilizing environmental scanning (transmission) electron microscopy and near-ambient pressure photoelectron spectroscopy/photoemission electron microscopy, we unravel a new adsorption-induced dispersion mechanism in such a typical oxidative dispersion process. The strong gas-metal interaction achieved by chemisorption of oxygen on nearly-metallic silver nanoclusters is the internal driving force for dispersion. In situ observations show that the dispersed nearly-metallic silver nanoclusters are oxidized upon cooling in oxygen atmosphere, which could mislead to the understanding of oxidation-induced dispersion. We further understand the oxidative dispersion mechanism from the view of dynamic equilibrium taking temperature and gas pressure into account, which should be applied to many other metals such as gold, copper, palladium, etc. and other reaction conditions.
氧化分散已广泛应用于烧结金属催化剂的再生和单原子催化剂的制备，这归因于氧化诱导的分散机制。然而，在分散过程中气体-金属-载体相互作用的相互影响，特别是气体-金属相互作用尚未得到很好的阐释。在此，我们展示了在还原/氧化条件下以及一氧化碳氧化反应过程中，银纳米结构在氮化硅表面的动态分散。利用环境扫描（透射）电子显微镜和近常压光电子能谱/光发射电子显微镜，我们揭示了在这种典型的氧化分散过程中一种新的吸附诱导分散机制。通过氧在近金属银纳米团簇上的化学吸附实现的强气体-金属相互作用是分散的内在驱动力。原位观察表明，分散的近金属银纳米团簇在氧气气氛中冷却时会被氧化，这可能会误导对氧化诱导分散的理解。我们从考虑温度和气体压力的动态平衡角度进一步理解了氧化分散机制，该机制应适用于许多其他金属，如金、铜、钯等以及其他反应条件。
