摘要
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 Bi2S3 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 ℃, led the predominant defect/vacancy densities to change from isolated bismuth vacancies （VBi） to septuple Bi3＋-sulfur vacancy associates （VBiBiBiSSSS）. Furthermore, the concentration of septuple BiB＋-sulfur vacancy associates increased as the calcined temperature was increased from 400 to 450 ℃. 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 I2（sol）, easily desorbs I-（sol）, and enhances the electrocatalytic activity of the nanostructures.
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 Bi2S3 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 ℃, led the predominant defect/vacancy densities to change from isolated bismuth vacancies （VBi） to septuple Bi3＋-sulfur vacancy associates （VBiBiBiSSSS）. Furthermore, the concentration of septuple BiB＋-sulfur vacancy associates increased as the calcined temperature was increased from 400 to 450 ℃. 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 I2（sol）, easily desorbs I-（sol）, and enhances the electrocatalytic activity of the nanostructures.
