3. Results and Discussion
3.1. Synthesis and morphology of cobalt-doped ZnO nanorods and
zirconium-doped TiO2 nanoparticles
Cobalt-doped ZnO nanorods were fabricated on FTO by
chemical bath deposition. Scanning electron microscope (SEM)
images of the doped nanorods are shown in Fig. 2. No phase
separation of the Co2+ dopant is observed in these images, which is
consistent with the growth of a solid solution of (Zn0.9Co0.1)O.
Dopant elements can alter the thermodynamics of crystal growth
and affect growth kinetics, [32–34] and this was reflected in
altered nanorod dimensions in this study. Compared to undoped
nanorods, the presence of Co2+ in solution increased the average
diameter from 600 nm to 1100 nm, increased the average length
increased from 5 mm to 6 mm, and decreased the number density
from 1.2
108 rods per cm2 to 0.9
108 rods per cm2. EDX analysis
of the broken rod cross-section (shown in Fig. 2c) shows the
presence of the Co2+ in the ZnO matrix with a ratio of Co/(Co + Zn)
equal to 0.08. The voids seen in the cross section have been
observed in other annealed ZnO nanorods