Baidya Tinku, Dutta Gargi, Hegde M S, Waghmare Umesh V
Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore, India.
Dalton Trans. 2009 Jan 21(3):455-64. doi: 10.1039/b814742f. Epub 2008 Nov 11.
Pd ion substituted Ce1-xMxO2-delta (M = Ti, Zr, Hf) have been prepared by a single step solution combustion method. Two atom% Pd ion substitution in the title compounds is confirmed by X-ray diffraction (XRD) and Pd ion charge state and redox properties have been determined by X-ray photoelectron spectroscopy (XPS) and H2/TPR studies. While Pd ion in CeO2 (Ce0.98Pd0.02O2-delta) showed higher catalytic activity for CO oxidation than Pd metal impregnated over CeO2, further increase in the catalytic activity is observed with Pd ion in Ce1-xTi(Hf)xO2 and a decrease in the activity with Pd ion in Ce1-xZrxO2. Effective charge on Pd ion could be varied by its substitution in these solid solutions Ce1-xMxO2 (M = Ti, Zr & Hf) and also in TiO2 compared to Pd ion in PdO. Effective positive charge on Pd ion is determined from the core level binding energy shift of Pd(3d5/2) peak with respect to Pd metal. Rate of CO oxidation increased and activation energy decreased with increase in effective charge on the Pd ion in the Pd ion substituted fluorites.
通过单步溶液燃烧法制备了钯离子取代的Ce1-xMxO2-δ（M = Ti、Zr、Hf）。通过X射线衍射（XRD）确认了标题化合物中钯离子的2原子%取代，并且通过X射线光电子能谱（XPS）和H2/TPR研究确定了钯离子的电荷状态和氧化还原性质。虽然CeO2（Ce0.98Pd0.02O2-δ）中的钯离子对CO氧化显示出比负载在CeO2上的钯金属更高的催化活性，但在Ce1-xTi（Hf）xO2中钯离子的催化活性进一步提高，而在Ce1-xZrxO2中钯离子的活性降低。与PdO中的钯离子相比，通过在这些固溶体Ce1-xMxO2（M = Ti、Zr和Hf）以及TiO2中取代钯离子，可以改变钯离子上的有效电荷。钯离子上的有效正电荷由Pd（3d5/2）峰相对于钯金属的核心能级结合能位移确定。在钯离子取代的萤石中，随着钯离子有效电荷的增加，CO氧化速率增加且活化能降低。
