Visible light-driven photocatalytic reduction of chromium (VI) using TiO2-modified carbon sphere hybrid photocatalyst

Abstract

Carbon spheres (CS) were synthesized by simple hydrothermal route and further modified with TiO2 shell (CSTS) to demonstrate photocatalytic reduction of Cr(VI). The bare CS and CSTS were characterized with X-ray diffraction, Raman spectroscopy, field emission scanning electron microscope, transmission electron microscope, Fourier transform infrared spectroscopy, UV–vis diffuse reflectance spectroscopy and steady-state photoluminescence. The hybrid CSTS photocatalyst showed improved visible light photocatalytic reduction toward Cr(VI), compared with pristine TiO2 and commercial TiO2 (P25). Porous CS catalysts when modified with TiO2 shell shows 100% reduction of Cr(VI) in 4 h under visible light illumination. Also enhanced visible light photocurrent (~ threefold) is observed for CSTS photocatalyst as compared to bare CS photocatalyst. Modification of TiO2 shell on carbon sphere suppresses the recombination of photogenerated excitons (e−/h+) as revealed from the photoluminescence study and enhanced light absorption due to scattering of light by the sphere framework of TiO2 shell and CS, thus enhancing the overall photocatalytic activity.