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对利用溅射技术制备的Pt/Al_2O_3和Pt-Sn/Al_2O_3模型催化剂,以透射电子显微镜研究了金属粒子在H_2气中加热过程的烧结情况。实验结果表明,随着加热温度的升高,催化剂品粒逐渐长大,但加热到700℃经2h后,Pt/Al_2O_3的晶粒比Pt-Sn/Al_2O_3的大,这可能是Sn对Pt晶粒烧结起抑制作用。如将晶粒已经长大的样品再在空气中于500℃加热2h,则晶粒发生再分散。另外,在H_2气中加热后的催化剂的电子衍射花样,在Pt/Al_2O_3样品中仍表现Pt的特征;而在Pt-Sn/Al_3O_3样品中则形成几种不同组成的合金,我们推测可能是在还原过程中Pt与Sn之间发生强相互作用。
The sintering of metal particles during heating in H 2 gas was investigated by transmission electron microscopy (TEM) for Pt / Al 2 O 3 and Pt-Sn / Al 2 O 3 catalysts prepared by sputtering. The experimental results show that as the heating temperature increases, the catalyst particles grow up gradually. However, the grain size of Pt / Al_2O_3 is larger than that of Pt-Sn / Al_2O_3 after heated to 700 ℃ for 2h, Grain sintering from the inhibition. If the grain has grown up in the sample and then heated in air at 500 ℃ 2h, the grain redispersed. In addition, the electron diffraction pattern of the catalyst heated in H 2 gas still shows the characteristics of Pt in the Pt / Al 2 O 3 samples; while in the Pt-Sn / Al 3 O 3 samples, several different compositions of the alloys are formed, There is a strong interaction between Pt and Sn during the reduction.