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. (C) 2012 Elsevier Inc. All rights reserved.