Hierarchically grown CdS/alpha-Fe2O3 heterojunction nanocomposites with enhanced visible-light-driven photocatalytic performance

Wide spectral responsive 3D hierarchical CdS/alpha-Fe2O3 heterojunction nanocomposites were synthesized through a facile chemical bath method under mild conditions, and used for the reduction of Cr(VI) into Cr(III) under visible light irradiation. The effects of CdS/alpha-Fe2O3 molar ratio in the nanocomposites on the crystal phases, microstructures, optical absorption properties, and photocatalytic reduction of Cr(VI) were investigated comparatively. It was found that the as-synthesized CdS/alpha-Fe2O3 nanocomposites with a suitable CdS content (e. g., the molar ratio of Fe : Cd = 1.25 : 3) had not only high visible-light-driven photocatalytic activity in the Cr(VI) reduction, but also good photocatalytic stability. The enhanced photocatalytic activity can be ascribed to some CdS nanoparticles closely contacting the alpha-Fe2O3 microflowers to form a heterojunction structure. These tight heterojunctions of the photocatalysts result in an efficient electron-hole pairs separation at the interface, followed by fast diffusion of photogenerated charge between CdS and alpha-Fe2O3, which is beneficial for separating the photogenerated carriers in space and improving the photocatalytic activity.