A novel route for preparing Ag₂Se-based micro-nanocomposites and their photocatalytic activity

A novel oil–water interface method was successfully used to prepare rod-shaped silver selenide (Ag₂Se) micro-nanoparticles from relatively low-toxic and cheap sodium selenosulfate by aging at 160 °C for 12 h. Then, under the same reaction conditions, AgCl/Ag₂Se and Ag/Ag₂Se micro-nanocomposites were synthesized by simply introducing different additives. The as-prepared micro-nanocomposites were characterized by the uses of XPS, XRD, SEM, BET, UV–vis, and PL. Cl⁻ plays a bifunctional role to act as the adsorbate and the source of AgCl. Under the irradiation of a fluorescent light (36 W), the photocatalytic activity of Ag₂Se-based micro-nanocomposites was evaluated by degradation of acid fuchsin (AF) and malachite green (MG) dyes in the presence of 0.6 wt.% H₂O₂. The results showed that the recombination of AgCl and the deposition of Ag exerted a significant influence on the light absorption of the particles. AgCl/Ag₂Se and Ag/Ag₂Se composites exhibited much higher catalytic activity than pure Ag₂Se with the same surface area, Ag/Ag₂Se composite particles have the best photodegradation performance, and the AF degradation rate is faster than MG. In aqueous solutions, positively charged Ag₂Se micro-nano particles can be easily combined with AF anionic dyes instead of MG cationic dyes, resulting in more efficient AF photodecomposition. The significant increase in photocatalytic activity of AgCl/Ag₂Se is mainly due to the heterojunction formed between AgCl and Ag₂Se components, reducing the recombination of electron and hole pairs. In the case of Ag/Ag₂Se composite material, the noble metal Ag acts as an electron trap to improve the separation of charges. In total, the high efficiency of the composite photocatalysts implies that it is of great significance in the degradation of environmental pollutants.