Synthesis and photocatalytic activity of anatase TiO2 xerogels: Effect of atomic radius of copper, cobalt, and cadmium dopants

This study investigates the influence of the atomic radii of copper, cobalt, and cadmium on the photocatalytic activity of anatase TiO2 xerogels synthesized via the solgel method. All samples were annealed at 550 °C for 20 min and crystallized into the pure anatase phase, as confirmed by XRD and Raman spectroscopy. Dopant incorporation into the TiO2 matrix reduced the grain size (from 24.01 to 9.78 nm) and decreased the bandgap energy (from 3.44 to 3.19 eV). Photocatalytic degradation of methylene blue (MB) revealed enhanced activity for doped samples, with degradation rates increasing from 71.65% for undoped TiO to 79.29%, 86.54%, and 94.13% for 2 at. % Cu-TiO2, 2 at. % Co-TiO2, and 2 at. % Cd-doped TiO2, respectively. Among the dopants, 2 at. % Cd-TiO2 exhibited the highest photocatalytic efficiency and the fastest degradation rate. Furthermore, the 2 at. % Cd-TiO2 sample demonstrated excellent stability, retaining more than 90% of its photocatalytic activity over six cycles with only a 4% loss in capacity.