BiOBr microspheres anchored with Cu2O nanoparticles and rGO: A Z-scheme heterojunction photocatalyst for efficient reduction of Cr(VI) under visible light irradiation

Photocatalytic reduction of hexavalent chromium (Cr(VI)) is an effective way to reduce its environmental risk. However, it remains a challenge to achieve a high removal rate in mild conditions. In order to efficiently remove Cr(VI) from water, a novel Z-scheme heterojunction composite photocatalyst rCB-20 (Cu 2 O/rGO/BiOBr, 20% Cu 2 O) was successfully prepared using a simple two-step strategy in this work. The characterizations of the catalyst show that the Z-scheme heterojunction formed between Cu 2 O and BiOBr is favorable for facilitating the separation of photogenerated carriers. The existence of rGO can reduce the resistance of electron transport. Therefore, the composite photocatalyst exhibits a very high photocatalytic activity in the photoreduction of Cr(VI). For example, using it to completely remove Cr(VI) with a concentration of 20 mg•L −1 in the pH = 4 solution only requires 40 min. Even the complete removal of the same concentration of Cr(VI) in neutral water at pH 7 does not take more than 90 min. Meanwhile, it possesses a high stability in catalytic activity and structure.