Fabrication of close-contact S-scheme Cr2Bi3O11-Bi2O3/Fe3O4@porous carbon microspheres based on in-situ reaction: Enhanced photo-Fenton wastewater treatment

Low photo-induced carrier recombination rate, exceptional light absorption, and advantageous recycling performance are crucial attributes of semiconductor photocatalyst for wastewater purification. Herein, based on in-situ reaction, close-contact S-scheme bismuth chromate/bismuth oxide/ferroferric oxide@porous carbon microspheres (Cr₂Bi₃O₁₁-Bi₂O₃/Fe₃O₄@PCs) (F-CBFP) was fabricated using alginates as precursor. Due to the abundance of functional groups on the porous carbon (PCs), Bi₂O₃ and Cr₂Bi₃O₁₁ nanoparticles (NPs) are in situ deposited onto the highly conductive 3D magnetic porous Fe₃O₄@PCs microsphere surface, which not only form tight interfacial contacts and reduces interfacial potential barriers but also prevent agglomeration or shedding of the NPs during photocatalytic reactions. Moreover, density functional theory (DFT) calculations further confirm that the formation of a robust built-in electric field (BIEF) within F-CBFP prompts photo-induced electrons in the conduction band (CB) of Bi₂O₃ to combine with holes in the valence band (VB) of Cr₂Bi₃O₁₁, effectively constructing a S-scheme heterojunction system. Also, Fe₃O₄ can act as a Fenton catalyst, activating the H₂O₂ generated by Cr₂Bi₃O₁₁ under illumination. In wastewater treatment, the obtained F-CBFP shows remarkable photo-Fenton degradation (towards methyl orange (97.8 %, 60 min) and tetracycline hydrochloride (95.3 %, 100 min)) and disinfection performance (100 % E. coli inactivation), and exceptional cyclic stability.