吸附态物种表面迁移对程序升温脱附的影响

EFFECT OF SURFACE MIGRATION OF ADSORBED SPECIES ON TPD SPECTRA

利用ＭｏｎｔｅＣａｒｌｏ（ＭＣ）方法研究了吸附态物种表面迁移对程序升温脱附谱图的影响。在ＭＣ模型中，催化剂表面用一个二维的方格网络表示，网络格点表示吸附活性位。两种不同的活性位完全随机地分布在表面上。模拟结果表明，两种吸附位的脱附活化能相差不太大时，表面迁移会使高温峰和低温峰发生重叠。而当两种脱附活化能相差比较大时，表面迁移会使高温峰提前出现，但峰位置不会发生明显的变化。

Effect of surface migration of adsorbed species on TPD spectra is investigated by means of Monte Carlo method In the MC model, a catalytic surface is represented by a twodimensional square lattice of 200×200 sites which indicate active sites on the surface Two kinds of active sites are randomly distributed on the lattice By the simulation, it is found that the surface migration can make the hightemperature peak overlap with the lowtemperature peak in the case of relatively small difference of the activation energies of adsorbed species in the two kinds of sites The hightemperature peak can appear early due to the surface migration when the difference of the activation energies is relatively large, however, no obvious variation in the location of the peak is found