Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore, 560012, India.
Dalton Trans. 2010 Nov 28;39(44):10768-80. doi: 10.1039/c0dt00480d. Epub 2010 Oct 4.
Nanocrystalline Ce(1-x)Fe(x)O(2-δ) (0 ≤ x ≤ 0.45) and Ce(0.65)Fe(0.33)Pd(0.02)O(2-δ) of ~4 nm sizes were synthesized by a sonochemical method using diethyletriamine (DETA) as a complexing agent. Compounds were characterized by powder X-ray diffraction (XRD), X-ray photo-electron spectroscopy (XPS) and transmission electron microscopy (TEM). Ce(1-x)Fe(x)O(2-δ) (0 ≤ x ≤ 0.45) and Ce(0.65)Fe(0.33)Pd(0.02)O(2-δ) crystallize in fluorite structure where Fe is in +3, Ce is in +4 and Pd is in +2 oxidation state. Due to substitution of smaller Fe(3+) ion in CeO(2), lattice oxygen is activated and 33% Fe substituted CeO(2)i.e. Ce(0.67)Fe(0.33)O(1.835) reversibly releases 0.31[O] up to 600 °C which is higher or comparable to the oxygen storage capacity of CeO(2)-ZrO(2) based solid solutions (Catal. Today 2002, 74, 225-234). Due to interaction of redox potentials of Pd(2+/0)(0.89 V) and Fe(3+/2+) (0.77 V) with Ce(4+/3+) (1.61 V), Pd ion accelerates the electron transfer from Fe(2+) to Ce(4+) in Ce(0.65)Fe(0.33)Pd(0.02)O(1.815), making it a high oxygen storage material as well as a highly active catalyst for CO oxidation and water gas shift reaction. The activation energy for CO oxidation with Ce(0.65)Fe(0.33)Pd(0.02)O(1.815) is found to be as low as 38 kJ mol(-1). Ce(0.67)Fe(0.33)O(1.835) and Ce(0.65)Fe(0.33)Pd(0.02)O(1.815) have also shown high activity for the water gas shift reaction. CO conversion to CO(2) is 100% H(2) specific with these catalysts and conversion rate was found to be as high 27.2 μmoles g(-1) s(-1) and the activation energy was found to be 46.4 kJ mol(-1) for Ce(0.65)Fe(0.33)Pd(0.02)O(1.815).
使用二乙三胺（DETA）作为络合剂，通过超声化学法合成了~4nm 尺寸的纳米晶 Ce(1-x)Fe(x)O(2-δ)（0 ≤ x ≤ 0.45）和 Ce(0.65)Fe(0.33)Pd(0.02)O(2-δ)。通过粉末 X 射线衍射（XRD）、X 射线光电子能谱（XPS）和透射电子显微镜（TEM）对化合物进行了表征。Ce(1-x)Fe(x)O(2-δ)（0 ≤ x ≤ 0.45）和 Ce(0.65)Fe(0.33)Pd(0.02)O(2-δ)在萤石结构中结晶，其中 Fe 处于+3 价，Ce 处于+4 价，Pd 处于+2 价。由于较小的 Fe(3+)离子在 CeO(2)中的取代，晶格氧被激活，33%的 Fe 取代 CeO(2)，即 Ce(0.67)Fe(0.33)O(1.835)在 600°C 以下可逆释放 0.31[O]，这比 CeO(2)-ZrO(2)基固溶体（Catal。今日 2002，74，225-234）的储氧容量更高或相当。由于 Pd(2+/0)(0.89 V)和 Fe(3+/2+)(0.77 V)与 Ce(4+/3+)(1.61 V)之间的氧化还原电位的相互作用，Pd 离子加速了 Ce(0.65)Fe(0.33)Pd(0.02)O(1.815)中 Fe(2+)到 Ce(4+)的电子转移，使其成为一种高储氧材料以及一种用于 CO 氧化和水汽变换反应的高活性催化剂。用 Ce(0.65)Fe(0.33)Pd(0.02)O(1.815)进行 CO 氧化的活化能被发现低至 38 kJ mol(-1)。Ce(0.67)Fe(0.33)O(1.835)和 Ce(0.65)Fe(0.33)Pd(0.02)O(1.815)也表现出对水汽变换反应的高活性。这些催化剂上 CO 转化为 CO(2)的转化率为 100% H(2)特异性，转化率高达 27.2 μmoles g(-1) s(-1)，活化能为 46.4 kJ mol(-1)，用于 Ce(0.65)Fe(0.33)Pd(0.02)O(1.815)。
