The simultaneous promotion of Cr (VI) photoreduction and tetracycline removal over 3D/2D Cu2O/BiOBr S-scheme nanostructures

Although the degradation of hexavalent chromium (Cr (VI)) or tetracycline hydrochloride (TC) in water bodies has been intensively studied, the degradation of mixed pollutants in the liquid phase is still an arduous challenge. In this paper, a series of Cu2O/BiOBr S-scheme composite photocatalysts were successfully prepared by a hydrothermal and subsequent precipitation method to purify the water body where Cr (Ⅵ) and TC coexist. The morphologies and photoelectrochemical characteristics of the prepared samples were characterized by XRD, FTIR, TEM, UV–vis, XPS, PL, EIS, and other methods. The optimal Cu2O/BiOBr with 15 wt% Cu2O (CB-15) provided the best photocatalytic activity. CB-15 exhibited a Cr (Ⅵ) reduction efficiency 21.75 times higher than BiOBr. The TC degradation efficiency of CB-15 was 1.21 times higher than Cu2O. It was interesting that the synergistic photocatalytic activity of CB-15 in the mixed system was improved. The reduction ability of Cr (Ⅵ) and the degradation ability of TC were increased by 1.67 times and 1.18 times, respectively. The enhanced activity of CB-15 was ascribed to the S-scheme heterojunction and 3D/2D structure. The S-scheme transfer mechanism in CB-15 could suppress the recombination of photogenerated carriers and thus prolong the fluorescence lifetime of carriers. While the 3D/2D heterostructure with a large number of contact areas and active sites could further promote the efficiency of the photocatalytic reaction. Notably, the photocatalyst still maintained an excellent degradation ability after four recycles. In general, this paper provided new insights into the design of 3D/2D S-scheme heterojunction photocatalysts and the degradation of mixed wastewater.