L-cystine-assisted Synthesis Of Ag₂S/CdS Nano Heterosturcture Via A Cation-exchange Approach At Room Temperature

Many transition metal chalcogenides, with proper conduction band and valence band, exhibit strong absorption in the visible region and have potential applications in photocatalysis including photocatalytic water decomposition to H2 as well as photodegradation of organic pollutants. However, the photocatalytic efficiency tends to be low and the catalyst is unstable and prone to light corrosion during the reaction period. The fast recombination of photogenerated e-/h+ is pairs is considered to be one of the main reasons for limiting the photocatalytic reaction efficiency. Therefore, the essential fundamentals of photocatalytic reaction is how to further extend the lifetime of the photoexcited charge and inhibit the facile recombination of e-/h+ is pairs. This thesis focuses on the on the environmental-friendly, low-cost liquid-phase synthesis and assembly of multi-metal sulfide heterostructured nano-materials under mild conditions to enhance the facile separation of photogenerated e-/h+ pairs as well as the charge transport.Hexagonal CdS nanorod was first synthesized in the mixed solution of dodecanethiol and ethylenediamine via a high-yield solvothermal approach. Based on the difference of Ksp value between Ag2S(Ksp=5.0×10-50) and CdS(Ksp=8.0×10-27), Ag2S/CdS dotted nanorod was slowly grown in aqueous solution(pH = 11~12) using NaOH as the pH value regulator by a mild cation-exchange technique at room temperature in the presence of L-cystine(low-cost, environmental-friendly) as the sulfur source and complexing agent. The as-synthesized products were characterized by XRD, EDS, TEM, HRTEM, XPS, FTIR and Uv-Vis techniques. The results indicated the formation of heterojunction between Ag2 S and CdS. This is helpful to promote the separation of photogenerated e-/h+ pairs as well as the charge transport, thus remarkably increasing the photocatalytic efficiency. In addition, the simple and environmentally benign synthetic approach will provide a new idea for the preparation of novel visible-light responsive photocatalyst composites that are are higly efficient, stable, environmental-benign and inexpensive.