Morphology and crystal-plane effects of Zr-doped CeO2 nanocrystals on the epoxidation of styrene with tert-butylhydroperoxide as the oxidant

The morphology effect of Zr-doped CeO2 was studied in terms of their activities in the selective oxidation of styrene to styrene oxide using tert-butyl hydroperoxide as the oxidant. In the present work, Zr-doped CeO2 nanorods exhibited the highest catalytic performance (yield of styrene oxide and TOF value) followed by nanoparticles and nanocubes. For the Zr-doped CeO2 nanorods, the apparent activation energy is 56.3 kJ/ mol, which is much lower than the values of catalysts supported on nanoparticles and nanocubes (73.3 and 93.4 kJ/ mol). The high resolution transmission electron microscopy results indicated that (1 0 0) and (1 1 0) crystal planes are predominantly exposed for Zr-doped CeO2 nanorods while (1 0 0) and (1 1 1) for nanocubes, (1 1 1) for nanoparticles. The remarkably increased catalytic activity of the Zr-doped CeO2 nanorods is mainly attributed to the higher percentage of Ce3+ species and more oxygen vacancies, which are associated with their exposed (1 0 0) and (1 1 0) crystal planes. Furthermore, recycling studies proved that the heterogeneous Zr-doped CeO2 nanorods did not lose its initial high catalytic activity after five successive recycles. (c) 2017 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. and Science Press. All rights reserved.