A visible-light-driven core-shell like Ag₂S@Ag₂CO₃ heterojunction photocatalyst with high performance in pollutants degradation

A series of Ag₂S-Ag₂CO₃ (4 % , 8 % , 16 % , 32 % and 40 % Ag₂S), Ag₂CO₃@Ag₂S (32 % Ag₂S) and Ag₂S@Ag₂CO₃ (32 % Ag₂S) heterojunction photocatalysts were fabricated by coprecipitation or successive precipitation reaction. The obtained catalysts were analyzed by N₂physical adsorption, powder X-ray diffraction(XRD), scanning electron microscopy(SEM), transmission electron microscopy(TEM), X-ray photoelectron spectroscopy(XPS), Fourier transform infrared spectroscopy(FT-IR), Raman spectroscopy(Raman) and UV-VIS diffuse reflectance spectroscopy(UV-VIS DRS). Under visible light irradiation, the influences of Ag₂S content and core-shell property on photocatalytic activity and stability were evaluated in studies focused on the degradation of methyl orange (MO) dye and phenol. Results showed that excellent photocatalytic performance was obtained over Ag₂S/Ag₂CO₃ heterojunction photocatalysts with respect to Ag₂S and Ag₂CO₃. With optimal content of Ag₂S (mass fraction of 32 % ), the Ag₂S-Ag₂CO₃ showed the highest photocatalytic degradation efficiency. Moreover, the structured property of Ag₂S/Ag₂CO₃ greatly influenced the activity. Compared with Ag₂S-Ag₂CO₃ and Ag₂CO₃@Ag₂S, core-shell like Ag₂S@Ag₂CO₃ demonstrated the highest activity and stability. The main reason for the boosting of photocatalytic performance was due to the formation of Ag₂S/Ag₂CO₃ heterojunction with well contacted interface and unique electron structures. Ag₂S/Ag₂CO₃ heterojunction could significantly increase the separation efficiency of the photo-generated electrons (e^-) and holes(h⁺), and production of oOH radicals. More importantly, the low solubility of Ag₂S shell could effectively protect the core of Ag₂CO₃, which further guarantees the stability of Ag₂CO₃.