(22e) Photocatalytic Enhancement of Titania Via Deposition of Metal Nanoparticles

Due to concerns about sustainable energy use, photocatalysis has attracted increased research interest in
recent years. In principle, photocatalysis can offset
some of the demand on fossil fuels compared to conventional catalysis by using
solar energy to provide the activation energy for catalysts. Major efficiency
improvements are still needed, however, before photocatalysis
becomes a practically and economically viable technology. Much current research
focuses on increasing the photo-efficiency of semiconductors by either decreasing
their band gaps or by decreasing exciton
recombination rates. Our group has previously shown for the first time that photoactivity persists and even increases at higher
temperatures (i.e., above 100°C). This work shows that the photoactivity
can be further enhanced in the range of 100-300°C via the deposition of metal nanoparticles such as Au and Ag on the surface of TiO₂.
It is proposed that the mechanism of enhancement is the migration of
photo-generated electrons to the unfilled bands of deposited metal particles,
which reduces the electron-hole recombination rate. Catalysts are characterized
via HAADF STEM and DRIFTS, and their photoactivity is
evaluated by CO oxidation in a novel quartz-cell plate reactor. Results for
these materials show that during UV illumination, CO oxidation activity is
higher for TiO₂ with deposited metal particles than at the same
temperature without UV, and at the same temperature for bare TiO₂,
with a maximum photocatalytic enhancement observed
around 190°C. The effect of metal loading and type on the enhancement is also
investigated. Preliminary results for (Ag,Au)@TiO₂
with core-shell structure will be shown.