Synthesis of BiOI/Bi4O5I2/Bi2O2CO3 p–n–p heterojunctions with superior photocatalytic activities

Abstract

A one-dimensional (1D) BiOI/Bi₄O₅I₂/Bi₂O₂CO₃ p–n–p heterojunction photocatalyst was synthesized by a low-temperature solution method using Bi₂O₃ nanorods as sacrificial templates. The formation mechanism of BiOI/Bi₄O₅I₂/Bi₂O₂CO₃ heterostructure was discussed in detail according to the results of IR, XPS, TEM, SEM mapping, XRD and SEM. Compared with pure BiOI, Bi₂O₂CO₃ and Bi₄O₅I₂, this ternary p–n–p heterojunction exhibited superior photodegradation efficiency of rhodamine B (100%) and methylene blue (97%) in 45 min under solar light irradiation, which was about 40, 25 and 10 times of pure BiOI, Bi₂O₂CO₃ and Bi₄O₅I₂, respectively. This enhanced photocatalytic performance was ascribed to the high separation rate of photo-generated carriers in the internal electric field due to the formation of p–n–p junctions and a relatively large BET surface area (36.29 g m⁻²). More importantly, 1D heterostructure is beneficial for the transport of photo-generated electron–hole pairs and further improves the rate of photocatalytic reaction. Radical scavenger experiments revealed that the photo-generated holes were primarily active species in the photocatalytic system. This work would offer a new insight into the design and fabrication of ternary p–n–p junction structures for photocatalytic applications.