Green synthesis of Mn-doped TiO2 nanoparticles and investigating the influence of dopant concentration on the photocatalytic activity

Abstract

• An environmentally friendly method for preparing photocatalysts to treat organic dyes. • A green synthesis approach is adopted to prepare Mn-doped TiO 2 nanoparticles. • Methylene blue is degraded most efficiently using a 0.05% Mn-TiO 2 catalyst. • 0.1 g L -1 of catalyst is found to remove 86% of Methylene blue after 35 minutes. • The regeneration of the Mn 4+ /Mn 2+ cycle is crucial for photocatalytic activity. A tea plant extract is used in the presence of titanium and manganese sources to synthesize three different concentrations of Mn x Ti 1-x O 2 (x=0.03, 0.05, and 0.1). By substituting Ti atoms for Mn, the lattice of TiO 2 is successfully incorporated with Mn. The degradation of Methylene Blue (MB) in the presence of visible light is used to test the photocatalytic activity of the synthesized samples. Among the Mn-doped TiO 2 samples, the highest degradation ratio is observed for samples with a dopant concentration of 0.05 at%. A dose of 0.1 g L -1 and 5 mM of Mn-TiO 2 is found to remove 86% of MB after 35 minutes of reaction. Mn x Ti 1-x O 2 is critically important for speeding up the MB degradation because of electron transfer between Mn and TiO 2 , and for the regeneration of the Mn 4+ /Mn 2+ cycle on its surface. Optical irradiation of the photocatalytic system under visible light led to higher visible photocatalytic activity than pure TiO 2 . We propose a novel and environmentally friendly method for preparing photocatalysts to treat organic dyes.