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

Abstract

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 56.3kJ/mol, which is much lower than the values of catalysts supported on nanoparticles and nanocubes (73.3 and 93.4kJ/mol). The high resolution transmission electron microscopy results indicated that (100) and (110) crystal planes are predominantly exposed for Zr-doped CeO2 nanorods while (100) and (111) for nanocubes, (111) 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 (100) and (110) 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.