Nanostructured metal oxide layers have become a prominent building block in a variety of fields related to advanced materials, including energy conversion, sensing, and environmental remediation. Photocatalytic decomposition of various pollutants (e.g., volatile organic compounds, dyes, and bacteria) is one of the main applications of these advanced materials. Specifically, photocatalysis provides a sustainable, efficient, and effective means to degrade a variety of organic contaminants from wastewater. The aim of this thesis is to synthesize nanostructured titanium dioxide (TiO2) layers on carbon fibers (CFs) to photocatalytically degrade methylene blue (MB), a model dye contaminant. In order to achieve efficient photocatalytic efficiency, two complementary synthetic methods were used, namely a wet chemical synthetic method and a Vapor Phase Infiltration (VPI). Wet chemical synthesis uses solution-based reactions, that result in metal oxide nanoparticles on the fiber surface. This synthetic method is a relatively inexpensive and straightforward way to produce nanoparticulate coatings with various crystallite sizes, which affect the available fiber surface. Moreover, this approach does not require any costly equipment. Conversely, VPI is utilized to deposit conformal and atomically controlled metal oxides infiltrated within the fiber uppermost surface. VPI provides coating uniformity and can be used to prepare different mass and crystallinity of TiO2. However, this process requires the use of specialized tools - specialized ALD-based rectors - in which the infiltration takes place.
In this thesis, The CFs@TiO2 were characterized by SEM, EDXRF, EDX, XRD, Raman spectroscopy (RS), and UV-Vis DRS spectroscopy, which confirmed the presence or incorporation (depending on the technique) of a nanostructured TiO2 layer onto the CFs. They helped to clarify the relationship between the method of synthesis, structural, and optical properties. The photocatalytic performance was evaluated through MB degradation by UV light irradiation. Generally, the deposition method chosen had a dramatic effect on the morphology, surface coverage, and activity of the final photocatalysts. The degradation kinetics and stability of the materials were systematically assessed.
This study demonstrates the feasibility of combining scalable fiber synthesis with multivalent synthetic routes for the environmental remediation of pollutants. The wet chemical synthesis and VPI provide a comparative framework for benchmarking and finding optimal pathways for the design of materials to serve as sustainable photocatalysts. The outcomes from this research will help further the environmental use of nanostructured metal oxides for photocatalytic applications.