Facile fabrication of sandwich-like BiOI/AgI/g-C₃N₄ composites for efficient photocatalytic degradation of methyl orange and reduction of Cr(VI)

Construction of heterojunction photocatalyst with excellent charge separation has attracted significant attention for solving the global energy crisis and environmental problems. Herein, a series of sandwich-structured BiOI/AgI/g-C₃N₄ composites were fabricated by a novel and facile method. The AgI was employed as a charge transmission bridge between BiOI and g-C₃N₄, which could result in more efficient charge transfer and better separation of charge carriers. The results indicated that the BiOI/AgI/g-C₃N₄ composites exhibited higher photocatalytic activity for the degradation of methyl orange (MO) and reduction of Cr(VI) than that of pure g-C₃N₄, BiOI, and BiOI/g-C₃N₄. The amount of AgI had a remarkable influence on the photocatalytic activity of the BiOI/AgI/g-C₃N₄ composites. Moreover, the BiOI/AgI/g-C₃N₄ composites exhibited high stability. Finally, a possible reaction mechanism on degradation of MO and reduction of Cr(VI) solutions over the composites was proposed. This work could facilitate a better understanding on the charge transfer process in the composite systems as well as provide a new approach to the rational design of novel advanced materials for practical photocatalytic application.