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首页> 美国卫生研究院文献>Scientific Reports >Oxygen vacancy clusters essential for the catalytic activity of CeO2 nanocubes for o-xylene oxidation
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Oxygen vacancy clusters essential for the catalytic activity of CeO2 nanocubes for o-xylene oxidation

机译：CeO2纳米立方体对邻二甲苯氧化的催化活性必不可少的氧空位簇

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摘要

Catalytic oxidation of o-xylene was investigated on CeO2 nanocubes calcined at 350, 450, 550, and 650 °C, among which the samples calcined at 550 °C exhibited the highest activity and long durability. Positron annihilation spectroscopy measurements revealed that the size and distribution of oxygen vacancies for CeO2 nanocubes could be tuned by carefully controlling the calcination temperature. An excellent linear correlation between a factor related to size and density of oxygen vacancy clusters and reaction rate of o-xylene oxidation was revealed on ceria nanocubes. This means that oxygen vacancy clusters with suitable size and distribution are responsible for catalytic reaction via simultaneous adsorption and activation of oxygen and o-xylene. Electron spin resonance spectra revealed that over the CeO2 cubes, water vapor significantly promoted the formation of ∙OH radicals with a sharp decrease in the signals relating to oxygen vacancies, accelerating the transformation of o-xylene to the intermediate benzoate species, resulting in an enhancement of catalytic activity. Water thus serves as a “smart” molecule; its introduction into the feed mixture further confirmed the key role of oxygen vacancies in the catalytic performance of CeO2 nanocubes. A possible mechanism of oxygen vacancy formation during the calcination process was also proposed.
机译：研究了在350、450、550和650 C煅烧的CeO2纳米立方体上对二甲苯的催化氧化，其中在550 C煅烧的样品表现出最高的活性和长的耐久性。正电子an没光谱测量表明，可以通过仔细控制煅烧温度来调节CeO2纳米立方体的氧空位的大小和分布。在二氧化铈纳米立方体上揭示了与氧空位簇的大小和密度相关的因素与邻二甲苯氧化反应速率之间极好的线性相关性。这意味着具有合适尺寸和分布的氧空位簇通过同时吸附和活化氧和邻二甲苯而引起催化反应。电子自旋共振谱显示，在CeO2立方体上，水蒸气显着促进∙OH自由基的形成，与氧空位有关的信号急剧下降，加速了邻二甲苯向中间苯甲酸酯种类的转化，从而增强了催化活性因此，水是“智能”分子。将其引入到进料混合物中进一步证实了氧空位在CeO2纳米立方体的催化性能中的关键作用。还提出了煅烧过程中氧空位形成的可能机理。

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