Fabrication of β-phase AgI and Bi₂O₃ co-decorated Bi₂O₂CO₃ heterojunctions with enhanced photocatalytic performance

Bi₂O₂CO₃ was co-decorated by β-phase AgI and Bi₂O₃ forming visible-light-active AgI(β)/Bi₂O₃(β)-Bi₂O₂CO₃ composite via simply calcining AgI/Bi₂O₂CO₃. The calcination temperature and time played vital role in regulating the structure as well as photocatalytic performance. Optimal AgI(β)/Bi₂O₃(β)-Bi₂O₂CO₃ was obtained after 325 ^◦C calcination for 2 h with 5% AgI. The ratio of Bi₂O₃ to Bi₂O₂CO₃ was estimated to be ca. 3:1 on the catalyst surface. The transformation process for n-type Bi₂O₂CO₃ to p-type Bi₂O₃(β) was monitored and verified by flat band potential measurements. Due to the presence of p-n junctions between p-type Bi₂O₃(β), n-type AgI(β) and Bi₂O₂CO₃, the optimized ternary composite displayed enhanced photocurrent density and reduced charge transfer resistance, which were beneficial for photocatalytic applications. Despite of decreased specific surface area, dramatically enhanced photocatalytic performance can be observed for simultaneous removal of Cr(VI) and phenol. For example, the estimated k_Cr(VI) and k_phenol on AgI(β)/Bi₂O₃(β)-Bi₂O₂CO₃ were 3.3 and 2.2 times relative to those on uncalcined AgI/Bi₂O₂CO₃, respectively. The optimized composite also displayed good stability in 4 successive cyclic runs.