Enhanced Cr(VI) photoreduction in aqueous solution using Nb2O5/CuO heterostructures under UV and visible irradiation

Due to the high energy required for activation of TiO2 in the photoreduction of Cr(VI) to Cr(III), the yield of the process is limited by the absorption of radiation up to 385 nm. This strongly restricts the potential use of solar light as energy source. Therefore, the development of a stable photocatalyst that can be activated under visible radiation is highly desirable for large-scale applications. Here we describe, for the first time, a Nb2O5/CuO heterostructure produced using a solvothermal procedure to nucleate CuO nanoparticles over commercial Nb2O5 microparticles. The heterostructures showed high photoreduction activity under visible irradiation and was suitable for Cr(VI) reduction in an aqueous medium. CuO nanoparticles were evenly distributed on the surface of the Nb2O5, with a junction formed between the oxides. The use of a weight ratio of 10% CuO on Nb2O5 provided the best photoreduction activity, with 84% reduction of Cr(VI) to Cr(III) after 210 min. The photoreduction reaction followed second order kinetics. The junction between the Nb2O5 and CuO resulted in improved photogenerated charge separation, leading to significantly increased photoreduction of Cr(VI) under both UV and visible irradiation. (C) 2016 Published by Elsevier B.V.