Reduced graphene oxide supported on Gd2MoO6-ZnO nanorod photocatalysts used for the effective reduction of hexavalent chromium

Abstract

Possible Photocatalytic reduction mechanism of Cr(VI) over the Gd 2 MoO 6 -rGO-ZnO. • Excellent photo reduction performance of toxic Cr(VI) to Cr(III) species. • Gd 2 MoO 6 -rGO-ZnO ternary catalyst shows suppressed charge recombination. • Gd 2 MoO 6 -rGO-ZnO is effective photoreduction of Cr(VI) under UV-light illumination. • The enhancing photocatalytic mechanism using the synthesized ternary catalyst was discussed. A reduced graphene oxide (rGO)-Gd 2 MoO 6 -ZnO nanocomposite was synthesized using a hydrothermal method, in which rod-shaped ZnO and plate-like Gd 2 MoO 6 were decorated on rGO sheets. The as-prepared photocatalyst was characterized using X-ray diffraction, optical studies, photoluminescence measurements, surface morphology, chemical states, and photocurrent density studies. A stable photocatalytic performance was achieved using the synergetic Gd 2 MoO 6 -rGO-ZnO composite catalyst during the reduction of Cr(VI) to benign Cr(III) compared with the performance achieved using bare and binary composite catalysts. The effects of various parameters, such as different weight ratios and solution pH, were investigated. An optimized pH of 4 was used for the effective reduction of Cr(VI) to Cr(III). The maximum photocatalytic reduction performance (94.5%) was achieved within 160 min. Photocurrent density and PL emission measurements confirmed the fast charge transfer and effective charge separation over Gd 2 MoO 6 -rGO-ZnO, which improved the Cr(VI) reduction. A photocatalytic Cr(VI) reduction mechanism for Gd 2 MoO 6 -rGO-ZnO was proposed.