Hierarchical ZnO porous microspheres and their gas-sensing properties

Materials with hierarchical and porous architectures often take on novel functional features. Here, we fabricate successfully the Zn4(OH)6CO3·H2O (ZCHH) microspheres which consist of the nanoflakes by using a simple hydrothermal process, and demonstrate that the ZCHH precursor can be transformed utterly to ZnO porous microspheres after calcination. Further comparative studies reveal that both urea and MEA play a critical role in producing such unique porous microspherical architecture. The likely formation mechanism of the porous microspheres is proposed based on the time-dependent experiments. As a consequence of the unique hierarchical and porous architecture, the microspheres show a large specific surface area due to the remarkable amount of petals and pores on them and therefore excellent gas-sensing properties.