Fast synthesis of CuS and Cu9S5 microcrystal using subcritical and supercritical methanol and their application in photocatalytic degradation of dye in water

Abstract Copper sulfides were synthesized through a fast and simple subcritical and supercritical methanol technique by controlling the reaction temperature. CuS and Cu 9 S 5 microcrystals with different particle sizes and morphologies were prepared. The composition, morphology, and structure of the products were analyzed using XRD, SEM, TEM, DLS, XPS, and FTIR. UV–vis was used to investigate their optical behaviors. Results show that spherical CuS and polyhedral Cu 9 S 5 with an average size of 200–600 and 200–500 nm were obtained at 150 and 260 °C for 15 min in subcritical and supercritical methanol, respectively. The UV–vis absorption spectroscopy of the samples reveals that the band gap energies of CuS and Cu 9 S 5 were 1.77 and 1.55 eV, respectively. CuS exhibited excellent photocatalytic degradation of methylene blue (MB) without the use of hydrogen peroxides, showing 85.4% degradation rate of MB after 5 h irradiation.