La_(1-x)Sr_xMnO_(3-δ)(x=0,0．4)纳米粒子的制备、表征及催化性能研究

Preparation, Characterization and Catalytic Performance of La_(1-x)Sr_xMnO_(3-δ)(x=0,0.4)Nanoparticles

采用水热合成法和柠檬酸络合法合成了La1-xSrxMnO3-δ(x=0,0．4)纳米粒子催化剂,应用X射线衍射(XRD),BET,高分辨扫描电子显微镜(HRSEM)、X光电子能谱(XPS)、程序升温还原(H2-TPR)及氧化态测定等技术表征了这些催化剂的物理性质,考察了其对乙酸乙酯氧化反应的催化活性。结果表明,所得催化剂均为单相菱方钙钛矿结构,比表面积20-33 m2·g-1,且水热合成法所得催化剂为分布均匀的短棒状粒子,粒径在30-60 nm之间。Sr的掺杂增加了催化剂的还原性,提高了催化活性。乙酸乙酯在催化剂上完全被氧化且无副产物生成。通过比较催化剂的比表面积、阳离子缺陷量(氧过量)和Mn4+浓度(可还原性)'可以认为La1-xSrxMnO3-δ的催化活性主要取决于其氧化还原性能。

La1-xSrxMnO3-δ(x=0, 0.4) nanoparticles were synthesized using the hydrothermal synthesis and citric acid complering methods. Techniques such as X-ray diffraction (XRD), high resolution scanning electron microscopy (HRSEM), X-ray photoelectron spectroscopy (XPS ), hydrogen temperature-programmed reduction (H2-TPR) as well as surface area measurements and oxi dation state titration were used to characterize the physi cal properties of these materials, and their catalytic per-formance was examined for the combustion of ethylace tate (EA). It was found that the La1-xSrxMnO3-δ(x =0, 0. 4) catalysts are single-phase and rhombohedrally- structured perovskites and their surface areas range from 20 to 33 m2·g-1. The catalysts derived from the hydrothennal route are unifonnly distributed 30-60 nm parti-cles with a short rod-shaped morphology. The doping of Sr increases the reducibility and hence enhances the catalytic activity. EA is oxidized completely and no partially oxidized side-products are formed over the catalysts. By comparing surface areas, cationic defect amounts (over-stoiehiometric oxygen) and Mn4+ concentrations (reducibility) of the catalysts, it can be concluded that the catalytic performance of La1-xSrxMnO3-δ is determined by their reduction-oxidation ability.