一维ZnO表面可控构建Co_(3)Mn_(1)纳米晶及其催化CO氧化性能

Controlled construction of Co_(3)Mn_(1)nanocrystals on one-dimensional ZnO surfaces for catalytic performance of CO oxidation

利用热分解法制备了结构明确的负载型纳米晶催化剂。在纳米晶成核和生长过程中加入一维ZnO纳米棒作为晶种,调控不同组分的纳米晶在ZnO纳米棒表面均匀生长,从而获得了结构明确的MnO/ZnO、Co_(3)O_(4)/ZnO、Co_(3)Mn_(1)/ZnO催化剂。透射电子显微镜(TEM)与X射线粉末衍射(XRD)结果显示,不同组分纳米颗粒都均匀分散在ZnO纳米棒表面。相对于MnO/ZnO和Co_(3)O_(4)/ZnO催化剂,Co_(3)Mn_(1)/ZnO催化剂在CO氧化反应中具有最佳的催化性能。在200 L·g_(cat)^(-1)·h^(-1)的气时空速下,Co_(3)Mn_(1)/ZnO催化剂起活温度为50℃,其T100(CO转化率达到100%时的温度)为200℃;利用X射线光电子能谱(XPS)对不同催化剂进行了分析,结果显示,Co_(3)Mn_(1)/ZnO催化剂的氧空位比MnO/ZnO催化剂提高了30%以上,从而使其具有较高的CO氧化催化性能。更为重要的是,Co_(3)Mn_(1)/ZnO复合纳米晶催化剂的活化能(39.4 k J·mol^(-1))远低于其它负载型纳米晶催化剂。

We have prepared well-defined supported nanocrystal catalysts using a thermal decomposition method.One-dimensional ZnO nanorods were used as crystalline seeds during nanocrystal nucleation and growth.The growth of nanocrystals with different components on the surface of ZnO nanorods was systematically controlled.Moreover,well-defined MnO/ZnO,Co_(3)O_(4)/ZnO,and Co_(3)Mn_(1)/ZnO catalysts were synthesized by a modified thermal decomposition approach.Transmission electron microscope(TEM)and X-ray powder diffraction(XRD)results showed that different nanocrystals were uniformly dispersed on the surface of as-synthesized ZnO nanorods.The Co_(3)Mn_(1)/ZnO catalyst exhibited the best catalytic performance of CO oxidation compared to the MnO/ZnO and Co_(3)O_(4)/ZnO catalysts.The Co_(3)Mn_(1)/ZnO catalyst can easily catalyze CO oxidation at a lower temperature(50℃)with sustainable durability.Moreover,the T100(the temperature when CO conversion reached 100%)of Co_(3)Mn_(1)/ZnO catalyst was 200℃at gas hourly space velocity of 200 L·g_(cat)^(-1)·h^(-1).The surface characterization of the different catalysts was performed by using X-ray photoelectron spectroscopy(XPS).The results revealed that the Co_(3)Mn_(1)/ZnO catalyst had approximately 30%more oxygen vacancy compared to the MnO/ZnO catalyst,resulting in a higher catalytic activity of the CO oxidation reaction.More importantly,the Co_(3)Mn_(1)/ZnO catalyst had a much lower apparent activation barrier(39.4 kJ·mol^(-1))than the other supported nanocrystal catalysts.