Department of Chemistry, Renmin University of China, Beijing 100872, People's Republic of China.
Phys Chem Chem Phys. 2011 Mar 7;13(9):3896-905. doi: 10.1039/c0cp01782e. Epub 2011 Jan 4.
Tetragonal ZrO(2)-CeO(2) solid solutions with composition Zr(1-x)Ce(x)O(2) (x = 0.1, 0.2, and 0.3) were synthesized in a citrate complexation route and characterized by XRD, XPS, UV-vis diffuse reflectance and ESR measurements. The formation of the homogeneous solid solution Zr(1-x)Ce(x)O(2) constructed the oxo-bridged bimetallic Zr(IV)-O-Ce(III) linkage between two neighboring flattened tetrahedrons of the structural framework. As compared to their parent oxides, the ZrO(2)-CeO(2) solid solutions exhibited optical absorption extending to longer wavelengths in the visible region. The red shift in the absorption spectrum was demonstrated to be partially due to a metal-to-metal charge transfer (MMCT) transition of the oxo-bridged Zr(IV)-O-Ce(III) linkage. The visible-light induced MMCT transition of Zr(IV)-O-Ce(III)→ Zr(III)-O-Ce(IV) resulted in the generation of the additional Ce(IV) and superoxide anion radical formed by the interaction of Zr(III) with adsorbed O(2). Catalytic activity evaluation revealed that the photoexcitation of the MMCT over the solid solution can initiate the degradation of RhB and 2,4-DCP upon visible-light irradiation, whereby Zr(III) and Ce(IV) act as a site-specific reducing and oxidizing center, respectively. The structure of the solid solution Zr(1-x)Ce(x)O(2) and the oxidation states of Zr and Ce species are also discussed in detail.
四方相 ZrO(2)-CeO(2)固溶体具有组成 Zr(1-x)Ce(x)O(2)（x = 0.1、0.2 和 0.3），通过柠檬酸盐络合路线合成，并通过 XRD、XPS、UV-vis 漫反射和 ESR 测量进行了表征。均匀固溶体 Zr(1-x)Ce(x)O(2)的形成构建了结构框架中两个相邻扁平化四面体之间的氧桥接双金属 Zr(IV)-O-Ce(III)键合。与它们的母体氧化物相比，ZrO(2)-CeO(2)固溶体表现出光学吸收延伸到可见光区域的更长波长。吸收光谱的红移被证明部分归因于氧桥接的 Zr(IV)-O-Ce(III)键合的金属到金属电荷转移（MMCT）跃迁。Zr(IV)-O-Ce(III)→Zr(III)-O-Ce(IV)的可见光诱导 MMCT 跃迁导致了额外的 Ce(IV)和超氧阴离子自由基的产生，这是由 Zr(III)与吸附的 O(2)相互作用形成的。催化活性评价表明，固溶体上的 MMCT 光激发可以在可见光照射下引发 RhB 和 2,4-DCP 的降解，其中 Zr(III)和 Ce(IV)分别作为特定位置的还原和氧化中心。还详细讨论了固溶体 Zr(1-x)Ce(x)O(2)的结构和 Zr 和 Ce 物种的氧化态。
