Design of a direct Z-scheme photocatalyst: Preparation and characterization of Bi2O3/g-C3N4 with high visible light activity

A direct Z-scheme photocatalyst Bi 2 O 3 /g-C 3 N 4 was prepared by ball milling and heat treatment methods. The photocatalyst was characterized by X-ray powder diffraction (XRD), UV–vis diffuse reflection spectroscopy (DRS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brunauer–Emmett–Teller (BET) surface areas, photoluminescence technique (PL), and electron spin resonance (ESR) technology. The photocatalytic activity was evaluated by degradation of methylene blue (MB) and rhodamine B (RhB). The results showed that Bi 2 O 3 /g-C 3 N 4 exhibited a much higher photocatalytic activity than pure g-C 3 N 4 under visible light illumination. The rate constants of MB and RhB degradation for Bi 2 O 3 (1.0   wt.%)/g-C 3 N 4 are about 3.4 and 5 times that of pure g-C 3 N 4 , respectively. The migration of photogenerated carriers adopts a Z-scheme mechanism. The photoexcited electrons in the CB of Bi 2 O 3 and photogenerated holes in the VB of g-C 3 N 4 are quickly combined, so the photoexcited electrons in the CB of g-C 3 N 4 and holes in the VB of Bi 2 O 3 participate in reduction and oxidation reactions, respectively. O 2 − , OH and h + are the major reactive species for the Bi 2 O 3 /g-C 3 N 4 photocatalytic system.