Carbon and silica interlayer influence for the photocatalytic performances of spindle-like α-Fe2O3/Bi2O3p–n heterostructures

Abstract

The p–n heterojunction is an effective structure to suppress the recombination of photogenerated charge carriers due to the built-in internal electric field. Herein, we successfully synthesize a spindle-like α-Fe2O3/Bi2O3 core–shell heterostructure, in which α-Fe2O3 is an n-type semiconductor and Bi2O3 is a p-type semiconductor. In comparison with pure α-Fe2O3 seeds, the α-Fe2O3/Bi2O3p–n heterojunction photocatalyst exhibits tremendous photocatalytic performance on the degradation of Rhodamine B (RhB) under illumination of visible light. In addition, we insert an interlayer between p–n heterostructure, similar to p–i–n heterostructure. The silicon oxide and carbon are selected as the interlayer due to its different conductivity. The as-obtained α-Fe2O3/C/Bi2O3 exhibits higher degradation rate than α-Fe2O3/SiO2/Bi2O3. The reason is attributed to the mesoporous structure of carbon layer and its high conductivity so that the photogenerated electrons can be easily transferred from the conduction band of α-Fe2O3 to the conduction band of Bi2O3 thereby promoting an effective separation of photogenerated electrons and holes. However, the introduction of interlayer reduces the photocatalytic activity due to the alteration of internal built-in electric field in the heterojunction. We envision that these results have potential applications for designing the heterostructural photocatalysts.