Enhanced photocatalytic reduction of Cr(VI) by Cu2O/Bi5O7I microrods composites under visible light

A novel Cu2O nanoparticles decorated Bi5O7I hybrid composite was prepared through precipitation transformation and in-situ co-precipitation method in this study. The phase structures, morphologies and optical properties of as-synthesized samples were characterized by XRD, SEM, TEM and UV-vis diffuse reflectance spectroscopy. Cu2O/Bi5O7I exhibits significantly improved photocatalytic activity in Cr(VI) reduction under visible light irradiation. When the mass percentage of Cu2O to Bi5O7I is 15 %, Cu2O/Bi5O7I composite has the best photocatalytic reduction for Cr(VI) with efficiency of 92.3 %, which is much higher than those of pure Bi5O7I and Cu2O. The photocatalysts exhibited good photocatalytic reduction stability after five recycles. BET, photoluminescence and electrochemical impedance spectroscopy (EIS) measurements demonstrate that the enhanced photoreduction activity for Cr(VI) may be ascribed to the greater visible light absorption intensity, increased specific surface areas, higher efficient charge separation and transfer of photo-generated electron-hole pairs. In addition, a possible photoreduction mechanism of Cu2O/Bi5O7I composite has been proposed according to the experimental results.