engleski

Lateral and vertical evolution of the compositional and morphological profiles in nanostructured photocatalytic titania thin films

Thin films of nanostructured titania comprising different levels of lateral and vertical microstructural order and surface chemistry were prepared via the anodization of titanium. We segmented and demystified the contributions that lead to nanostructured titania and affected its photocatalytic behaviour to: (1) specific compositional (less dominant) and (2) specific (surface) morphological differences (substantial), in the as- achieved films. To shed more light on the contributions, we partitioned these films by chemically and morphologically distinctive constituents ; (1) top porous non-stoichiometric titania, (2) mid tubular nanoformations, and (3) bottom dense titania. Morphology of the films was described using electron microscopy, and synchrotron grazing incidence X-ray scattering/diffraction. Narrow range of synthetic conditions allowed preparing of ordered, macroscopically homogeneous nanotubes for photovoltaics. Interestingly, somewhat different, distorted tubular nanoformations were better suited for the photo-degradation of salicylic acid (fit by pseudo-second order). In this case, rutile traces in anatase tubular formations were commonly observed, synergistically boosting photodegradation. Broad characterisations reasons the photodegradation in order of importance to: (1) controlling the evolution of type of porosity and presence of defects in the films, (2) controlling the ratio and vertical profile of anatase-to-rutile, and (3) observing the surface chemistry changes, i.e. the presence of substoichiometric titania.

synchrotron GID and GISAXS; scanning electron microscopy; surface chemistry; immobilised photocatalyst; salicylic acid; anodized titania-nanotube-arrays

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