氧存在下钙钛矿LaCoO3硫化过程的XPS研究

摘要

It was found in our previous study that the process of activation-sulfurization of LaCoO3 plays a necessary role in the catalytic reduction of SO2 with CO to element S in the presence of oxygen. In order to explain the phenomenon, the process of activation-sulfurization of LaCoO3 in the presence of oxygen was studied by XPS, XRD and TEM methods. The valence variety on LaCoO3 surface in various processes of activation-sulfurization was investigated. When LaCoO3 was pre-poisoned by SO2, the adsorbed oxygen on its surface was absence, the chemical shift of binding energy of Co 2p(3/2) was more than 1.0 eV, the La 3d double peak turned unobvious, and at the same time the S4+ appeared on the surface, indicating that the perovskite was overlapped by the strongly adsorbed SO2 species. The results of XRD and TEM showed that after poisoned by SO2 no new phase appeared on the surface of perovskite LaCoO3. However, after activation-sulfurization the surface adsorbed oxygen reappeared, corresponding to LaCoO3, Co3O4 and CoSO4, Co had three valence states, La 3d double peak got clarity, S2- and S6+ appeared on the surface of LaCoO3. During the activation-sulfurization of LaCoO3 in the presence of oxygen, the SO2-poisoning on perovskite supplied S2- species to sulfurize the perovskite La-CoO3, and the surface adsorption oxygen made perovskite structure stable.