Transforming type-I to type-II heterostructure photocatalyst via energy band engineering: A case study of I-BiOCl/I-BiOBr

Abstract

Double visible light driven type-II heterostructure composites display highly efficient separation efficiency of photocharges due to the matching energy band structure. On the basis of the energy band engineering strategy, a novel flower-like heterostructured I-BiOCl/I-BiOBr composite was designed and synthesized by a simple deposition-precipitation method. The as-prepared I-BiOCl/I-BiOBr composites exhibited outstanding photocatalytic properties toward degradation of organic pollutants under visible light irradiation (λ>400nm). Comparatively, 20% I-BiOCl/I-BiOBr showed the highest photocatalytic activity owing to the best separation efficiency of photocharges. Based on the Mott-Schottky analysis, the I-BiOCl and I-BiOBr formed new I− ion doping energy level located on top of the valence bands of BiOCl and BiOBr, respectively. The doping effects presented two advantages: (1) making I-BiOCl and I-BiOBr possess favorable visible light absorption and (2) transforming type-I BiOCl/BiOBr structure to typical type-II I-BiOCl/I-BiOBr system. The strong visible light absorption of I-BiOCl and I-BiOBr as well as the I-BiOCl/I-BiOBr heterojunction interface with highly efficient separation of photocharges resulted in largely enhanced photocatalytic activity of I-BiOCl/I-BiOBr composite system. This study reveals that energy band structure modulation induced by ion doping can overcome the shortcoming of single-component photocatalyst, and play significant role for assembling double visible light driven type-II heterostructure composites.