Unusual reactivity of visible-light-responsive AgBr–BiOBr heterojunction photocatalysts

AgBr–BiOBr heterojunction photocatalysts with varying loadings of AgBr (<5.0 wt% AgBr) were synthesized through an effective co-precipitation method and used for the photodegradation of Rhodamine B under visible-light irradiation. Superior photocatalytic activities relative to that of pure BiOBr were observed on the AgBr–BiOBr catalysts with low AgBr loading (up to 0.5 wt%). Higher AgBr loadings (>0.5 wt%) lead to isolated AgBr species and reduced photocatalytic activity. Among such catalysts, the AgBr (0.2 wt%)–BiOBr exhibits the highest visible-light-responsive photoactivity, which can decolorize Rhodamine B within 30 min. However, these AgBr–BiOBr materials gradually lost their photoactivity in the cycling photocatalytic tests. Possible mechanisms for both the enhanced photocatalytic activity and deactivation of the AgBr–BiOBr heterojunctions were proposed on basis of theoretical speculation and experimental observations.