We demonstrate the fabrication of a large area 2-dimensional
(2-D)
binary colloidal assembly of polymeric microspheres (μ-spheres)
and TiO2 nanoparticles (NPs). TiO2 NPs near
the surface of poly(methyl methacrylate) (PMMA) μ-spheres in
aqueous dispersion exerted attractive depletion force between μ-spheres,
allowing the formation of the well-ordered composite monolayer having
hexagonal close-packed (hcp) structure on the air–water interface
which can be transferred to a solid substrate. Subsequent drying and
calcination of the composite film resulted in an “egg plate”
structured TiO2 film. When additional TiO2 dispersion
was spin-coated on the composite monolayer, an interesting honeycomb
structured TiO2 film was obtained. After the photodeposition
of Au NPs on the honeycomb structured TiO2 film for an
enhanced absorptivity of visible light, the film was tested as a photoelectrode
for photocatalytic water splitting. Owing to the large surface area
of the well-ordered 2-D porous structure, a photoanode with the honeycomb-structured
TiO2 thin film exhibited a 67 times higher photocurrent
density (PCD) for water splitting compared to the value from nanoporous
TiO2 photoanode with the same thickness.
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