期刊
APPLIED CATALYSIS B-ENVIRONMENTAL
卷 245, 期 -, 页码 546-554出版社
ELSEVIER SCIENCE BV
DOI: 10.1016/j.apcatb.2019.01.025
关键词
Perovskites; Catalytic ozonation; Oxygen vacancies; Density functional theory; Reactive oxygen species
资金
- National Natural Science Foundation of China [21606253]
- National Science Fund for Distinguished Young Scholars of China [51425405]
- Science Foundation of China University of Petroleum, Beijing [2462016YJRC013]
- Beijing Natural Science Foundation [8172043]
- Major Science and Technology Program for Water Pollution Control and Treatment [2017ZX07402003, 2017ZX07402001]
La-based perovskites are catalytically active owing to the oxygen vacancies, redox metal centers of B sites and surface hydroxyl groups. Nevertheless, the insights into these active centers on environmental catalysis are still insufficient. In this study, hierarchical mixed oxides perovskite microspheres were synthesized for catalytic ozonation over oxalic acid and benzotriazole. LaMn4O., with LaMnO3-delta as the dominant crystal phase, demonstrated superior catalytic activity to Mn2O3 and LaMnO3 synthesized from citric acid sol-gel method. Temperature-programmed desorption of NH3 (NH3-TPD) and pyridine-Fourier transform infrared spectroscopy (pyridine-FTIR) tests proved Lewis acid as the main acid type. Temperature-programmed reduction of H-2 (H-2-TPR), O-2-TPD and X-ray photoelectron spectroscopy (XPS) analysis indicated the presence of oxygen vacancies and mixed valences of Mn in the crystal structure facilitated the catalytic process. Moreover, the content of oxygen vacancy was calculated by iodometric titration method. With the aid of theoretical calculations, oxygen vacancies were found to exhibit a strong affinity toward ozone adsorption, where ozone molecules spontaneously dissociated into reactive oxygen species (ROS) such as O-2(center dot-) and O-1(2). The B site of Mn facilitated ozone decomposition by extending the O-O bond of ozone due to the electron transfer from Mn3+/Mn4+ redox cycle. In-situ EPR and quenching tests confirmed the contribution of O-2(center dot-) and O-1(2) in benzotriazole degradation along with (OH)-O-center dot. This study stepped further to unveil the ozone adsorption/decomposition and ROS generation on nanoscale perovskite-based composites.
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