Photocatalytic activity of chromium-doped titania in degrading congo red and methylene blue under visible light

Abstract

A series of 0.5 – 4 mol% Cr-doped TiO2 photocatalysts synthesized via sol-gel method were tested over photodegradation of congo red and methylene blue under visible light irradiation. Presence of Cr dopant has induced anatase-rutile phase transition, resulted in high rutile percentage of 45% in the material. Besides, the addition of Cr has extended the absorption wavelength of TiO2 to visible light region. As evidenced from the photoluminescence analysis, electron-hole recombination rate of Cr-doped TiO2 decreased when the Cr content was varied from 0.5 to 3 mol%. Despite using the same series of photocatalysts, the optimum Cr dopant which gave the best photocatalytic activity was different: 3 mol% Cr-doped TiO2 was the best photocatalyst for removing congo red while 1 mol% Cr-doped TiO2 was the best photocatalyst for removing methylene blue. Apparently, the nature of targeted subtract in photodegradation affected the photocatalytic performance of the Cr-doped TiO2.