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.

Keywords

Carbon sphere / Cr(VI) reduction / Photocatalyst / Steady-state emission

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