热脱附谱表征SmMnO_3表面氧的吸附态

Adsorption States of Oxygen on SmMnO_3 Characterized by Thermal Desorption Spectroscopy

从SmMnO_3的清洁表面上吸附O_2后的热脱附谱图中发现,气相氧不仅在SmMnO_2表面吸附,而且也大量进人由于高温(820K)抽空而造成的晶格氧缺陷中.实验结果表明O_2在SmMnO_3的表面吸附存在着两种化学吸附态,且均为二级吸附,即O_2以离解方式吸附在SmMnO_3的表面,同时对氧的热脱附谱采用脱附速率等温线法处理,结果得到这两种化学吸附态的平均脱附活化能分别为67.0和93.9kJ/mol,其中脱附活化能较大的那一种吸附态仅在较高温度下吸附时才出现,因而该吸附态应具有较大的吸附活化能.

Thermal desorption spectroscopy (TDS) was used to characterize the adsorption states of oxygen on the perovskite-type oxide SmMnO3 under the ultra high vacuum condition. It was found from TDS obtained in this experiment that oxygen not only adsorbed on SmMnO3, but also entered numberously into crystal defects of lattice oxygen in SmMnO3 caused by heating up to 820K in vacuum chamber. The experimental results indicated that there are two kinds of chemical adsorption states for oxygen on SmMnO3, and these two kinds are both adsorption states of second order. Their average activation energies of desorption obtained by the method of desorptin rate isotherms are 67. 0 and 93. 9 kJ/mol respectively. Of these two kinds, the adsorption state corresponding to the higher desorption activation energy only emerges at the higher adsorption temperature, so this adsorption state is of the higher adsorption activation energy.