Morphology Control of TiO<sub>2</sub> Nanoparticle
in Microemulsion and Its Photocatalytic Property
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Abstract
TiO<sub>2</sub> nanoparticles with
controlled morphology and high
photoactivity were prepared using a microemulsion-mediated hydrothermal
method in this study, and the particles were characterized by means
of TEM, XRD, BET, and BJH analysis. As the hydrothermal temperature
is elevated, mean pore diameter, crystalline size, and crystallinity
of the particles increase gradually, while the surface area decreases
significantly, and the morphology changes from a spherical into a
rod-like shape. The morphology transition mechanism of the TiO<sub>2</sub> crystal has been put forward based on a decrease in intensity
of the microemulsion interface and an increase in collision efficiency
between droplets with increasing the hydrothermal temperature. The
photocatalytic activity of the TiO<sub>2</sub> particles synthesized
at 120–200 °C is relatively low due to their weak crystallinity,
though they have high surface area of 146–225 m<sup>2</sup>/g and small crystalline size of 6–10 nm. However, the TiO<sub>2</sub> samples prepared at 250–350 °C with low surface
area (28–90 m<sup>2</sup>/g) exhibit high activity on the degradation
of Rhodamine B (RhB), which is comparable or higher than that of the
commercial P-25. The reason is ascribed to their high crystallinity
that determines material activity in this temperature region. This
study reveals that the effects of the surface area, crystallinity,
and crystalline size on TiO<sub>2</sub> activity are interdependent,
and the balance between these factors is important for improving the
photoactivity of the catalyst
