Facile synthesis of AgI/BiOI-Bi2O3 multi-heterojunctions with high visible light activity for Cr(VI) reduction

AgI sensitized BiOI-Bi 2 O 3 composite (AgI/BiOI-Bi 2 O 3 ) with multi-heterojunctions was prepared using simple etching-deposition process. Different characterization techniques were performed to investigate the structural, optical and electrical properties of the as-prepared photocatalysts. It was found that the ternary AgI/BiOI-Bi 2 O 3 composite exhibited: (1) improved photocurrent response, (2) smaller band gap, (3) greatly reduced charge transfer resistance and (4) negative shift of flat band potential, which finally led to easier generation and more efficient separation of photo-generated electron-hole pairs at the hetero-interfaces. Thus, for the reduction of Cr(VI), AgI/BiOI-Bi 2 O 3 exhibited excellent photocatalytic activity under visible light irradiation at near neutral pH. AgI/BiOI-Bi 2 O 3 was optimized when the initial molar ratio of KI to Bi 2 O 3 and AgNO 3 to Bi 2 O 3 was 1:1 and 10%, respectively. The estimated k Cr(VI) on optimized AgI/BiOI-Bi 2 O 3 was about 16 times that on pure Bi 2 O 3 . Good stability was also observed in cyclic runs, indicating that the current multi-heterostructured photocatalyst is highly desirable for the remediation of Cr(VI)-containing wastewater.