Institute of Atmospheric Sciences, Shanghai Key Laboratory of Atmospheric Particle Pollution and Prevention (LAP3), Department of Environmental Science and Engineering, Fudan University , Shanghai 200433, China.
Jiangsu Collaborative Innovation Center of Atmospheric Environment and Equipment Technology (CICAEET), Nanjing University of Information Science and Technology , Nanjing, Jiangsu 210044, China.
Environ Sci Technol. 2017 Feb 21;51(4):2304-2311. doi: 10.1021/acs.est.6b04340. Epub 2017 Feb 10.
The involvement of a great amount of active oxygen species is a crucial requirement for catalytic oxidation of benzene, because complete mineralization of one benzene molecule needs 15 oxygen atoms. Here, we disperse single silver adatoms on nanostructured hollandite manganese oxide (HMO) surfaces by using a thermal diffusion method. The single-atom silver catalyst (Ag/HMO) shows high catalytic activity in benzene oxidation, and 100% conversion is achieved at 220 °C at a high space velocity of 23 000 h. The Mars-van Krevelen mechanism is valid in our case as the reaction orders for both benzene and O approach one, according to reaction kinetics data. Data from H temperature-programmed reduction and O core-level X-ray photoelectron spectra (XPS) reveal that Ag/HMO possesses a great amount of active surface lattice oxygen available for benzene oxidation. Valence-band XPS and density functional theoretical calculations demonstrate that the single Ag adatoms have the upshifted 4d orbitals, thus facilitating the activation of gaseous oxygen. Therefore, the excellent activation abilities of Ag/HMO toward both surface lattice oxygen and gaseous oxygen account for its high catalytic activity in benzene oxidation. This work may assist with the rational design of efficient metal-oxide catalysts for the abatement of volatile organic compounds such as benzene.
大量活性氧物种的参与是苯催化氧化的关键要求，因为一个苯分子的完全矿化需要 15 个氧原子。在这里，我们通过热扩散法将单个银原子分散在纳米结构的水钠锰矿型氧化锰（HMO）表面上。单原子银催化剂（Ag/HMO）在苯氧化中表现出很高的催化活性，在 220°C 时，在 23000 h 的高空速下即可达到 100%的转化率。根据反应动力学数据，我们的反应中存在 Mars-van Krevelen 机制，因为苯和 O 的反应级数都接近 1。H 程序升温还原和 O 芯能级 X 射线光电子能谱（XPS）的数据表明，Ag/HMO 具有大量可用于苯氧化的活性表面晶格氧。价带 XPS 和密度泛函理论计算表明，单个 Ag 原子具有上移的 4d 轨道，从而促进了气相氧的活化。因此，Ag/HMO 对表面晶格氧和气相氧的优异活化能力解释了其在苯氧化中的高催化活性。这项工作可能有助于合理设计用于去除挥发性有机化合物（如苯）的高效金属氧化物催化剂。
