| Summary: | 碩士 === 逢甲大學 === 化學工程學系 === 106 === In this study, a series of biomimetic nanostructured chitosan films grafted with titanium dioxide (TiO2) were prepared for photocatalytic reduction of carbon dioxide.
The hydrophilic biopolymer chitosan (CS) was chosen as the support for photocatalyst to develop nature-based photocatalyst films with high efficiency and low toxicity. The preparation parameters were tuned and evaluated to elucidate their effect on the photocatalytic reaction. First, the cross-linking agent, glutaraldehyde (GA) was introduced to CS film to improve the denseness of CS matrix. The replication of the micro-nano structure of natural leaves to the surface of CS was conducted by PDMS-nanocasting technique. The amine groups and hydroxyl groups from chitosan structure would graft titanium dioxide to the surface of the film. The immersion time of titanium dioxide precursor with CS was adjusted to prepare a series of photocatalytic composite films (CS-TiO2). The SEM images confirmed the presence of biomimetic surface on CS films, and the denseness of film with the addition of GA was improved. Significantly, the biomimetic film has a surface contact angle of 137º, which was higher than that of pure CS film (06º), indicating enhanced hydrophobicity. XPS and FT-IR results confirmed the successful bonding of the functional groups of chitosan and titanium dioxide. TGA analysis showed that the addition of cross-linking agent and biomimetic structure improve the thermal stability of the film. The UV-VIS spectra showed that a series of CS films containing TiO2 have a characteristic absorption edge of TiO2. Notably, the formulation of TiO2 used in this study can form a photoactive TiO2 crystal phase under a heat treatment with relatively low temperature (150ºC). Obvious differences in the loading capacity of TiO2 and absorption edge were revealed between samples with cross-linking structure or with biomimetic structure. In this study, UVA (8W) light source was used to investigate the photocatalytic activity of carbon dioxide reduction. CS-TiO2 composite films can convert carbon dioxide into carbon monoxide, and trace amount of methanol and hydrogen. The best CO yield in 12 hours obtained in this study was 0.84 μmol/g.
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