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Interaction-Induced Self-Assembly of Au@La2O3 Core–Shell Nanoparticles on La2O2CO3 Nanorods with Enhanced Catalytic Activity and Stability for Soot Oxidation

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journal contribution
posted on 18.03.2019 by Qiangqiang Wu, Jing Xiong, Yilin Zhang, Xuelei Mei, Yuechang Wei, Zhen Zhao, Jian Liu, Jianmei Li
The sintering resistance of supported Au nanoparticle (NP) catalysts is crucial to their practical application in heterogeneous catalysis reactions. Herein, a series of Au@La2O3 core–shell nanoparticle catalysts supported on the surfaces of La2O2CO3 nanorods (Aun@La2O3/LOC-R) were successfully synthesized via the method of interaction-induced self-assembly. Supported Au NPs with uniform size are deposited on the surfaces of La2O2CO3 nanorods by the gas bubbling-assisted membrane reduction (GBMR) method. La2O3 shell layers spontaneously formed and then partially coated the surface of Au NPs for interaction-induced self-assembly of Au@La2O3 core–shell NPs during the process of calcination at 600 °C. The strong interaction between Au NPs and La2O3 oxides increases the density of active sites (oxygen vacancies) for enhancing the adsorption–activation properties of O2. Aun@La2O3/LOC-R catalysts show high catalytic activity and stability for soot oxidation under the conditions of loose contact between soot and catalyst. The catalytic activities (T50, TOF) of Au4@La2O3/LOC-R catalyst for soot oxidation are 375 °C and 1.15 × 10–3 s–1, respectively. On the basis of the results of various physicochemical characterizations, the strong metal (Au)–oxide (La2O3) interactions and the increase in active oxygen species of Aun@La2O3/LOC-R catalysts are responsible for enhancing the catalytic activity of soot oxidation. The Au@La2O3 core–shell nanostructure can improve catalytic stability and suppress sintering of supported Au NPs during catalytic soot oxidation. The catalytic mechanism of soot oxidation is proposed and discussed, in which the catalytic oxidation of NO to NO2 over Au@La2O3 core–shell NPs is the key step for catalytic soot oxidation; the active sites at the interface of the Au core and La2O3 shell can promote catalytic NO oxidation. Aun@La2O3/LOC-R catalysts show promise in practical applications for diesel soot oxidation.