Kozlov Sergey M, Neyman Konstantin M
Departament de Química Física and Institut de Quimica Teòrica i Computacional (IQTCUB), Universitat de Barcelona, C/Marti i Franques 1, 08028 Barcelona, Spain.
Phys Chem Chem Phys. 2014 May 7;16(17):7823-9. doi: 10.1039/c4cp00136b.
Cerium dioxide is a compound important for heterogeneous catalysis, energy technologies, biomedical applications, etc. One of its most remarkable properties is low O vacancy (Ovac) formation energy Ef. Nanostructuring of ceria was shown to decrease Ef and to make the oxide material more active in oxidative reactions. Here we investigate computationally formation of Ovac on CeO2(111) surfaces nanostructured by steps with experimentally observed structures. To facilitate the search for Ovac + 2Ce(3+) configurations that yield the lowest Ef values we proposed and employed an efficient computational scheme where DFT + U calculations were preceded by a pre-screening procedure based on the results of plain DFT calculations. Ef values on the steps were calculated to be up to 0.7 eV lower than on a regular CeO2(111) surface. Some energetically stable Ovac + 2Ce(3+) configurations were found to include subsurface Ce(3+) ions. The present results quantify to what extent the roughness of the CeO2(111) surface affects its reducibility.
二氧化铈是一种在多相催化、能源技术、生物医学应用等领域具有重要意义的化合物。其最显著的特性之一是氧空位（Ovac）形成能Ef较低。氧化铈的纳米结构化已被证明可以降低Ef，并使氧化物材料在氧化反应中更具活性。在此，我们通过计算研究在具有实验观测结构的台阶状纳米结构化CeO2(111)表面上Ovac的形成。为了便于寻找产生最低Ef值的Ovac + 2Ce(3+)构型，我们提出并采用了一种高效的计算方案，即在基于普通DFT计算结果的预筛选程序之后进行DFT + U计算。计算得出台阶上的Ef值比常规CeO2(111)表面低达0.7 eV。发现一些能量稳定的Ovac + 2Ce(3+)构型包含次表面Ce(3+)离子。目前的结果量化了CeO2(111)表面粗糙度对其还原性的影响程度。
