Correlation between types of defects/vacancies of Bi2S3 nanostructures and their transient photocurrent

Crystalline nanostructures possess defects/vacancies that affect their physical and chemical properties. In this regard, the electronic structure of materials can be effectively regulated through defect engineering; therefore, the correlation between defects/vacancies and the properties of a material has attracted extensive attention. Here, we report the synthesis of (B)i(2)S(3) microspheres by nanorod assemblies with exposed {211} facets, and the investigation of the types and concentrations of defects/vacancies by means of positron annihilation spectrometry. Our studies revealed that an increase in the calcined temperature, from 350 to 400 degrees C, led the predominant defect/vacancy densities to change from isolated bismuth vacancies (V-Bi) to septuple Bi3+-sulfur vacancy associates (V-BiBiBiSSSS). Furthermore, the concentration of septuple Bi3+-sulfur vacancy associates increased as the calcined temperature was increased from 400 to 450 degrees C. The characterized transient photocurrent spectrum demonstrates that the photocurrent values closely correlate with the types and concentrations of the predominant defects/vacancies. Our theoretical computation, through first principles, showed that VBiBiBiSSSS strongly absorbs I-2(sol), easily desorbs I-(sol), and enhances the electrocatalytic activity of the nanostructures.