A novel exposed facet dependent topological transformation mechanism from hydrozincite microspheres into hierarchical mesoporous ZnO structures

摘要

Distinct from normal hierarchical mesoporous ZnO structures exposed with (2 1 10) facets derived from polycrystal hydrozincite precursors exposed with (010) facets, single-crystal hydrozincite precursors with exposed (001) facets were prepared by a hydrothermal method assisted with sodium citrate and then topologically transformed into hierarchical mesoporous ZnO microspheres with exposed (0001) facets by calcination. To reveal the transformation process, a novel exposed facet dependent topological transformation mechanism was proposed as follows. Firstly, C-O bonds and -OH bonds in Zn-5(CO3)(2)(OH)(6) were broken with H2O and CO2 gases releasing; secondly, the remaining Zn atoms and O atoms rearranged their positions, leading to a transformation from a unit cell of monoclinic hydrozincite into eight unit cells of wurtzite ZnO based on their relationship of crystal lattice parameter. As a result, the (010) and (001) facets of hydrozincite can be transferred into the (2 -1 -10) and (0001) facets of wurtzite ZnO, respectively. In this sense, the exposed facets of hydrozincite precursors determined the exposed facets of ZnO microano structures. Therefore, the transformation mechanism can be also used to synthesize other metal oxide structures with special exposed facets. (C) 2017 Published by Elsevier B.V.