Comparative analysis between ZrO2 and TiO2 in physical properties and photocatalytic performance

This study investigates the structural, optical, and photocatalytic properties of TiO₂ and ZrO₂ nanostructures, focusing on the impact of 1000°C annealing. Both materials were synthesized via high-energy ball milling, followed by cold-pressing and calcination. Comprehensive characterization, including XRD, SEM, EDAX, Raman, FTIR, BET, and UV-Vis-NIR spectroscopy, provided insights into their microstructural evolution and optical behavior. Annealing significantly enhances crystalline and crystallite size in both materials. TiO₂ underwent a crucial anatase-to-rutile phase transformation, increasing rutile content from 6.25% to 12.08%, which is vital for its photocatalytic efficiency due to beneficial heterojunction formation. ZrO₂ maintained its monoclinic phase, primarily showing improved structural perfection. Optical studies revealed a decrease in band gap for both materials after annealing (TiO₂ from 3.27 eV to 3.12 eV; ZrO₂ from 4.34 eV to 4.17 eV), attributed to enhanced crystallinity and reduced quantum confinement, promoting broader light absorption. The photocatalytic performance was assessed through Methylene Blue (MB) degradation under visible light (Vis). ZrO₂ exhibited superior degradation efficiency compared to TiO₂, despite its larger band gap, which was linked to its higher specific surface area and localized states facilitating electron trapping and reducing electronhole recombination. These findings emphasize the critical roles of the high ball milling method and annealing-induced structural modifications of TiO₂ and ZrO₂ nanostructures.