Hydrothermal growth of overlapping ZnO nanorod arrays on the porous substrate and their H2 gas sensing

ZnO nanorod arrays (ZNAs) were prepared on a metakaolin (MK)-based porous substrate via a seeding-hydrothermal method. The spherical poly methyl methacrylate (PMMA) microspheres were employed as the pore former to obtain homogeneous porous structure on the MK-based substrates. Various characterization methods were used to investigate the effects of the porous structure on the morphological and structural properties of the ZNAs. The results indicated that the alignment degree of the ZNAs decreased significantly with the enhancement of the apparent porosity of the substrate. The ZNAs prepared on the MK-based substrate with the PMMA content of 30 wt% exhibited an overlapping morphology with an average diameter and length of 88 nm and 570 nm, respectively. Gas sensing measurements revealed that the response value of the overlapping ZNAs to 1000 ppm H(2 )at the operating temperature of 225 degrees C was 9.2, which is four times higher than that of the vertical ZNAs grown on the MK-based non-porous substrate. It confirms that the porous structure of the asprepared substrates favors for the growth of the overlapping ZNAs, and the enhanced H-2 gas sensing performance might be primarily related to the more effective adsorption sites and the modulation of the potential barrier at the junctions of the overlapping morphology.