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首页> 外文期刊>Acta Crystallographica, Section B. Structural Science >A new structural transformation mechanism in catalytic oxides
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A new structural transformation mechanism in catalytic oxides

机译：催化氧化物的新结构转变机理

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During dynamic reduction of vanadyl pyrophosphate using in situ electron microscopy and diffraction under controlled reaction conditions, recurrent dislocation of atoms is observed, which leads to the formation of extended defects by a glide shear mechanism. Ordering of the glide shear defects leads to a new structure by transforming the orthorhombic vanadyl pyrophosphate into an anion-deficient tetragonal structure. These defects are formed close to the surface and the nature of the defects is such that they accommodate the misfit between the reduced surface layers containing anion vacancies and the underlying unreduced bulk. The glide shear planar defects (GS) essentially preserve anion vacancies and do not lead to a lattice collapse, and are distinct from the well known crystallographic shear planes (CS, which eliminate anion vacancies leading to lattice collapse). In important complex oxides such as vanadyl pyrophosphates, and in a variety of model ReO3- and V2O5-based oxides used as catalysts, my in situ studies suggest that glide shear is the most effective defect mechanism by which the catalysts accommodate nonstoichiometry and continue to operate in partial oxidation reactions. Anion vacancy formation resulting from the oxide reduction is the driving force for the generation of glide misfit defects and their ordering can give rise to new phases or structures in oxides. The studies have important implications in oxide catalysis and, more generally, in oxide crystallography.
机译：在使用原位电子显微镜动态还原和在受控反应条件下进行衍射的过程中，焦磷酸钒酸钒的动态还原过程中，观察到原子的反复位错，这通过滑移剪切机制导致形成扩展的缺陷。滑移剪切缺陷的有序化通过将正交六钒氧焦磷酸转化为阴离子缺陷的四方结构而产生了新的结构。这些缺陷形成在靠近表面的位置，并且缺陷的性质使得它们可以适应包含阴离子空位的还原表面层与下面未还原的松散层之间的不匹配。滑移剪切平面缺陷（GS）基本上保留了阴离子空位，并且不会导致晶格塌陷，并且不同于众所周知的晶体学剪切平面（CS，它消除了导致晶格塌陷的阴离子空位）。在重要的复杂氧化物如焦磷酸氧钒中，以及在各种用作催化剂的基于ReO3-和V2O5的模型氧化物中，我的原位研究表明，滑移剪切是最有效的缺陷机理，通过这种机理，催化剂可适应非化学计量并继续运行在部分氧化反应中。由氧化物还原引起的阴离子空位形成是产生滑动失配缺陷的驱动力，并且它们的有序化可以在氧化物中产生新的相或结构。这些研究对氧化物催化，更广泛地说，对氧化物晶体学具有重要意义。

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