BiOCO/red phosphorus S-scheme heterojunction for H evolution and Cr(VI) reduction.

Red phosphorus (RP) has a suitable energy band structure and excellent photocatalytic properties. However, there are some problems, such as low quantum efficiency and serious photogenerated electron-hole recombination. The S-scheme heterostructure shows great potential in facilitating the separation and transfer of photogenerated carriers and obtaining strong photo-redox ability. Herein, hydrothermally treated red phosphorus (HRP) was combined with BiOCO to construct BiOCO/HRP S-scheme heterojunction composite. The BiOCO content was optimized, and the 5 %BiOCO/HRP composite obtained at 5 %BiOCO mass fraction exhibited the strongest photoreduction ability. The Cr(VI) photoreduction and photolytic hydrogen production rates were as high as 0.22 min and 157.2 μmol •h, which were 7.3 and 3.0 times higher than those of HRP, respectively. The promoted photocatalytic activity could be attributed to the formation of S-scheme heterojunctions, which accelerated the separation and transfer of useful photogenerated electron-hole pairs, while enhancing the recombination of relatively useless photogenerated electron-hole pairs, thereby resulting in the highest photocurrent density (17.3 μA/cm) of the 5 %BiOCO/HRP composite, which was 1.6 and 4.3 times higher than pure BiOCO (10.5 μA/cm) and pure HRP (4.0 μA/cm), respectively. This work would provide an advanced approach to enhance the photocatalytic activity of RP.