Phase development and photocatalytic ability of gel-derived P-doped TiO₂

P-doped titanium dioxide (TiO₂) nanoparticles were synthesized using a sol-gel method. The ethanol solution of Ti(OC₂H₅)₄ was mixed with an aqueous solution of H₃PO₄ to undergo hydrolysis and polycondensation at 90 °C for 4 h. The resultant solids were centrifugally filtered, dried, and then calcined at different temperatures, followed by chemical and physical characterization. At an atomic ratio of P/Ti = 0.03, the formed P-doped TiO₂ can preserve its anatase structure at 900 °C for 3 h, with no formation of other phases. Further increasing the P/Ti atomic ratio in the P-doped TiO₂ may stabilize the anatase–TiO₂ at even higher temperatures but may lead to the formation of TiP₂O₇ or (TiO)₂P₂O₇. A test of photocatalysis showed that the P-doped TiO₂ nanoparticles, with a P/Ti ratio = 0.03 and after being calcined at temperatures between 400 and 800 °C, can decompose ⩾98 mol.% of the methylene blue (MB) after 30 min of irradiation by 365-nm ultraviolet light, while P25 particles can only decompose 71 mol% of the MB.