• Investigation of non-isothermal kinetics of anatase–bronze TiO 2 and Ag-modified TiO 2 . • Precursor decomposition and rutile formation occur in two kinetically distinct stages. • Complementary ICTAC kinetic models are applied to understand kinetics. • Ag modification promotes early transformation but hinders rutile growth kinetics. • Nucleation and growth processes are kinetically decoupled by Ag incorporation. In this work, the non-isothermal thermo-kinetics and phase transition processes in mixed-phase anatase-bronze titanium dioxide (TiO 2 ) (MP–TiO 2 ) nanostructures and Ag-modified MP–TiO 2 nanostructures are explored. The samples are prepared by a solution-controlled precipitation method, in which the addition of silver precursors causes a ‘gel-like’ growth process and produces an interconnected morphology with a higher density. X-ray diffraction patterns and Raman spectra verify the coexistence of tetragonal anatase and monoclinic phases of TiO 2 (bronze) in both samples. Thermal analyses show dual transition processes during hydroxide to oxide transformation and anatase/ bronze to rutile phase transition. The kinetics of transformation are studied using different non-isothermal methods that complement each other, such as Kissinger peak analysis, isoconversional methods of Friedman and Kissinger-Akahira-Sunose, and model-based Coats-Redfern analysis. The data reveal that Ag modification lowers the apparent activation energy of the low-temperature hydroxide-to-oxide transformation but raises it substantially for the anatase/bronze-to-rutile transformation, in contrast to its effect on lowering the transformation temperature. This immediately reveals that there is a decoupling of nucleation versus growth, where Ag functions as an agent facilitating rutile nucleation shortly after transformation onset but acts as an inhibitor in the growth of different phases.
Khatri et al. (Wed,) studied this question.