Zhang Lei, Wang Sheng, Lv Lirong, Ding Ya, Tian Dongxu, Wang Shudong
Dalian National Laboratory for Clean Energy, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, P. R. China.
University of Chinese Academy of Sciences, Beijing 100049, P. R. China.
Langmuir. 2021 Feb 2;37(4):1410-1419. doi: 10.1021/acs.langmuir.0c02841. Epub 2021 Jan 24.
Manganese oxides with varied Mn valance states but identical morphologies were synthesized via a facile thermal treatment of γ-MnOOH. Also, their catalytic performance on ozone decomposition was investigated following the order of MnO < MnO < MnO < MnO-H-200. In combination with X-ray diffraction (XRD), scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET), transmission electron microscopy (TEM), H-temperature-programmed reduction (TPR), O-temperature-programmed desorption (TPD), and X-ray photoelectron spectroscopy (XPS) characterization, it was deduced that the superior O decomposition capacity for MnO-H-200 was strongly associated with abundant oxygen vacancies on its surface. Among MnO, MnO, and MnO, the difference in O decomposition efficiency was dependent on the divergent nature of oxygen vacancy. Density functional theory (DFT) calculation revealed that MnO and MnO possessed lower formation energy of oxygen vacancy, while MnO had the minimum desorption energy of peroxide species (O*). It was deduced that the promotion of the O decomposition capability was attributed to the easier O* desorption. Insights into the deactivation mechanism for MnO-H-200 further validated the assumptions. As the reaction proceeded, adsorbed oxygen species accumulated on the catalyst surface, and a portion of them were transformed to lattice oxygen. The consumption of oxygen vacancy led to the deactivation of the catalyst.
通过对γ-MnOOH进行简便的热处理，合成了具有不同锰价态但相同形态的锰氧化物。此外，按照MnO < MnO < MnO < MnO-H-200的顺序研究了它们对臭氧分解的催化性能。结合X射线衍射（XRD）、扫描电子显微镜（SEM）、布鲁诺尔-埃米特-泰勒（BET）、透射电子显微镜（TEM）、氢程序升温还原（TPR）、氧程序升温脱附（TPD）和X射线光电子能谱（XPS）表征，推断出MnO-H-200优异的臭氧分解能力与其表面丰富的氧空位密切相关。在MnO、MnO和MnO中，臭氧分解效率的差异取决于氧空位的不同性质。密度泛函理论（DFT）计算表明，MnO和MnO具有较低的氧空位形成能，而MnO具有过氧化物物种（O*）的最低脱附能。推断出臭氧分解能力的提高归因于更容易的O*脱附。对MnO-H-200失活机制的深入研究进一步验证了这些假设。随着反应的进行，吸附的氧物种在催化剂表面积累，其中一部分转化为晶格氧。氧空位的消耗导致催化剂失活。
