Shape controlled nanoparticles for enhanced photocatalytic applications

This work explores the development of shape-controlled nanomaterials and systematic investigation of the structure–function relationship of advanced photocatalytic materials to examine the degradation of aqueous and gas pollutants in order to address major environmental challenges posed by emerging pollutants in complex water matrices. This includes the degradation of emerging pollutants (Phenol, Methomyl, and Diclofenac), NOₓ abatement, and photoreforming hydrogen production. It highlights the critical role of shape-controlled TiO₂ synthesis, material design, and detailed characterisation, including SEM, XRD, FTIR, XPS, UV-VIS studies, HPLC, TOC analysis and applied photodegradation of pollutants to overcome key limitations of photocatalysis such as limited light utilisation, charge carrier recombination, and mass transfer resistance. The major contribution is the hydrothermal synthesis of shape- and size-controlled TiO₂ nanostructures, demonstrating the strong influence of temperature, pH, and reaction time on morphology and crystal facet exposure. In this context, a series of shape- and morphology-controlled TiO2 nanomaterials were developed, including Nanocuboids, Nanorods, Bipyramids (truncated and bipyramids), nanowires, nanoflowers, and TiO₂ nanobelts, which were successfully applied for the degradation of emerging environmental pollutants. Photocatalytic studies revealed that morphology plays a decisive role in performance. Shape-controlled TiO₂ characterised by favourable facet orientations exhibited enhanced charge carrier dynamics and strong pollutant–surface interactions, enabling complete mineralisation of phenol, methomyl, and diclofenac in both ultrapure water and alkaline stormwater. These findings emphasise the importance of morphological engineering for tailoring photocatalysts to specific environmental applications. Further investigation was carried out to enhance performance through the incorporation of reduced graphene oxide (rGO), which showed improved light absorption and charge separation, leading to higher degradation rates compared to conventional TiO₂ and demonstrating strong synergistic effects for complex pollutant remediation. For gas pollutant degradation, a custom-designed portable photoreactor was utilised to assess intrinsic photocatalytic activity and NOₓ abatement studies, where shape-controlled TiO₂-based nanomaterials exhibited significant improvements in NOₓ abatement efficiency and high selectivity. Photocatalytic hydrogen evolution studies attributed success to an optimised balance of surface area, active sites, efficient light scattering, and enhanced charge separation, resulting in reduced electron–hole recombination. Comparative studies were conducted to summarise hydrogen production. Furthermore, layered double hydroxide (ZnAl-LDH)-based systems were explored, where calcined LDHs were transformed into mixed metal oxides (MMO) and have shown suitable NOₓ abatement, high selectivity, and low NO₂ release. Developed LDH heterostructures have shown promising applications. Finally, TiO₂-incorporated plasma electrolytic oxidation (PEO) coatings were developed to investigate the inert incorporation of TiO₂ onto PEO surfaces, introducing the concept of TiO₂-based photocatalytic functional coatings, which demonstrated enhanced corrosion protection and offered durable and functional surfaces for wastewater remediation. Overall, this work bridges materials synthesis and structural-property relationships with fundamental photocatalytic science and practical environmental applications, demonstrating that shape-controlled nanostructures, heterostructure engineering, and materials design innovation provide a robust framework for developing sustainable, efficient, and scalable photocatalytic technologies for air and water pollution control