Speaker
Description
Modification of titanium dioxide (TiO₂) with noble metals such as gold (Au) and platinum (Pt) is a primary strategy for enhancing its performance in photocatalysis, sensing, and energy conversion. However, a systematic comparative study of how these dopants influence the thermal evolution of TiO₂ across a wide range of temperatures remains limited. In this work, the influence of Au and Pt dopants on the structural and microstructural evolution of TiO₂ was systematically investigated from 100 to 1100 °C. Undoped, Au-doped (5 wt%), and Pt-doped (5 wt%) TiO₂ nanoparticles were synthesised via the sol-gel route and annealed. X-ray diffraction revealed a temperature-dependent anatase-to-rutile phase transformation in all samples, with notable dopant-induced differences. At 600 °C, the onset of rutile was observed in undoped and Pt-doped TiO₂, whereas the Au-doped sample remained purely anatase, indicating that Au initially stabilises the anatase phase—likely due to substitutional Au³⁺ ions. Above 700 °C, Au reduced to metallic form, and by 900 °C, the transformation was complete for all samples. At ≥900 °C, Au-doped samples formed Au-Ti intermetallic compounds (e.g., AuTi₃), which accelerated rutile nucleation and grain growth. In contrast, metallic Pt detected at ≥900 °C did not delay the transformation onset but remained as a separate phase without forming intermetallics. Crystallite size calculations indicated that Pt suppressed coarsening, while Au promoted grain growth at higher temperatures. Scanning electron microscopy corroborated these findings, showing morphological evolution from fine agglomerates to larger sintered grains. Distinct differences in particle size distribution and agglomeration behaviour were observed between doped and undoped systems, highlighting the role of dopants in modulating microstructural development. The combined analyses reveal that Au acts as a low-temperature stabiliser but a high-temperature destabiliser, whereas Pt exhibits weaker overall influence on transformation kinetics. These findings provide a valuable foundation for developing thermally robust photocatalytic materials.
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