分别用扫描透射-高角环形暗场像(HAADF-STEM)和高分辨电子显微技术(HREM)表征了氧化态和硫化态Mo/Al2O3,Mo/6%TiO2-Al2O3,Mo/12%TiO2-Al2O3催化剂中MoO3颗粒尺寸和MoS2片晶的层数与长度,发现氧化态催化剂中MoO3颗粒的平均尺寸从Ti修饰前的0.7 nm增加到修饰后的1.0 nm;硫化态催化剂中MoS2片晶的平均层数从1.1增加到1.2,平均长度从3.0 nm增加到3.2 nm.并从金属-载体相互作用理论解释了其形成机理.基于以上结果,根据MoO3颗粒和MoS2片晶中钼原子数变化,研究了催化剂硫化过程中金属晶粒的生长演变过程.%High angle annular dark field-scanning transmission electron microscopy (HAADF-STEM) and high resolution electron microscopy (HREM) techniques were used to study the size of MoO3 and the average length and layer numbers of MoS2 slabs after sulfidation,respectively,in Mo/Al2O3,Mo/6%TiO2-Al2O3 and Mo/12%TiO2-Al2O3 catalysts.It is found that TiO2 modification makes the size of MoO3 particle increases from 0.7 nm to 1.0 nm in oxidized catalyst,the average layer numbers of MoS2 increases from 1.1 to 1.2 layers in sulfided catalyst,while the length increases from 3.0 nm to 3.2 nm.These phenomena could be well explained by the theory of metal-support interaction (MSI).Based on above results,the transformation from MoO3 particles to MoS2 slabs was investigated according to the change of Mo atom numbers in each crystal.
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