Holmium and Erbium-catalyzed in synthesis of PVP/TiO2 composites with improved photocatalytic degradation activity of methylene blue dye: Experimental and DFT insights

Porous titanium dioxide (TiO 2 ) was synthesized by incorporating polyvinylpyrrolidone (PVP) polymer. However, its application is limited due to its poor absorption of visible light. In this study, trivalent lanthanide metals (Ho 3+ and Er 3+ ) were added to sol-gel-produced crystalline tetragonal rutile phase TiO 2 to enhance light absorption and photocatalytic degradation efficiency. X-ray diffraction (XRD) analysis revealed that the crystallite size decreased with doping. Additionally, doping was found to increase the absorption bands and reduce photoluminescence (PL) quenching. The resulting porous photo- and electroactive materials were capable of degrading methylene blue dye in an aqueous solution through photocatalysis after sufficiently absorbing UV light. Er-doped TiO 2 (Er-TiO 2 ) exhibited superior performance in photocatalytic degradation efficiency (PCDE) compared to Ho-doped TiO 2 (Ho-TiO 2 ) and undoped TiO 2 , attributed to its enhanced light absorption, porous structure, and lower electrochemical impedance solution resistance (EIS). The resistance values were as follows: 30.1 Ω for Er-TiO 2 , 49.6 Ω for Ho-TiO 2 , and 59.2 Ω for TiO 2 . Density functional theory (DFT) calculations indicated that electronegative charge transfers were responsible for the photodegradation mechanism observed in the experimental data. • Porous TiO 2 doped with Ho 3+ and Er 3+ was prepared with sol-gel method. • TiO 2 absorption increases with dopants. • PL was also quenched with doping process leading to high photodegradation efficiency. • CV and EIS performance indicates Er-TiO 2 as the best performing material. • Er-TiO 2 shows better photodegradation efficiency than Ho-TiO 2 .