57Fe Mössbauer Spectroscopy of Ir-Fe Catalysts for Preferential CO Oxidation in H2

New insights on the interaction between Ir and Fe oxide are reported. Three Ir-Fe catalysts were prepared by different impregnation sequences of an Al2O3 support. Co-impregnation gave a better catalyst for the preferential CO oxidation in H2 (PROX) reaction. Microcalorimetry data showed that the adsorption of CO and H2 were different. Quasi in situ Mössbauer data of the three catalysts after reduction, reoxidation, and PROX reaction showed that a strong interaction between Ir and Fe affected the redox properties of the Ir-Fe catalysts. CO conversion was proportional to the concentration of the Fe2+(a) species, thus, Fe2+(a) was an active site in the PROX reaction. The impregnation sequence influenced the interaction between Ir and Fe and consequently, the amount of the active Fe2+(a) species. A strong Ir-Fe interaction stabilized the active Fe2+ sites for activating O2.

摘要： 采用不同浸渍顺序制备了三种 Ir-Fe 催化剂, 其 CO 选择氧化 (PROX) 反应活性差别很大, 其中共浸渍的 Ir-Fe 催化剂活性最高. 吸附量热研究表明, 三种催化剂的 H2 和 CO 吸附存在差别. 通过对三种催化剂还原后、再氧化和反应后准原位 57Fe 穆斯堡尔谱的研究, 得到各种 Fe 物种信息. 结果表明, 三种制备方法影响催化剂中 Ir-Fe 相互作用强度, 导致催化剂中 Fe 物种的氧化还原性能不同. 催化剂中 Fe2+(a) 的含量与 CO 转化率呈正比关系, Fe2+(a) 是 PROX 反应过程中活化氧的活性中心. 浸渍顺序改变了 Ir-Fe 间相互作用强度, 从而改变 Fe2+(a) 物种含量, 影响 PROX 反应活性. Ir-Fe 间的相互作用可以稳定活化氧的 Fe2+(a) 物种, 为今后研究金属-金属间的相互作用提供借鉴.

Fe2+(a) species of IrFe/Al2O3 was responsible for CO oxidation under H2-rich conditions, and the amount of the active Fe2+(a) relates closely with the Ir-Fe interaction.Figure optionsDownload as PowerPoint slide