Bi2O2CO3/red phosphorus S-scheme heterojunction for H2 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 Bi2O2CO3 to construct Bi2O2CO3/HRP S-scheme heterojunction composite. The Bi2O2CO3 content was optimized, and the 5 %Bi2O2CO3/HRP composite obtained at 5 %Bi2O2CO3 mass fraction exhibited the strongest photoreduction ability. The Cr(VI) photoreduction and photolytic hydrogen production rates were as high as 0.22 min-1 and 157.2 μmol •h-1, 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/cm2) of the 5 %Bi2O2CO3/HRP composite, which was 1.6 and 4.3 times higher than pure Bi2O2CO3 (10.5 μA/cm2) and pure HRP (4.0 μA/cm2), respectively. This work would provide an advanced approach to enhance the photocatalytic activity of RP.