Sonochemistry synthesis and enhanced photocatalytic H₂- production activity of nanocrystals embedded in CdS/ZnS/In₂S ₃ microspheres

ZnS and CdS nanocrystals with a size of 5-10 nm embedded in CdS/ZnS/In ₂S₃ microspheres have been successfully synthesized by a sonochemistry method at room temperature and normal pressure without the use of templates or surfactants. The as-prepared products have been characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), EDX line spectrum, high-angle annular dark-field imaging (HAADF), UV-visible diffuse reflectance spectra (UV-vis) and photoluminescence (PL) spectra. The reaction process in the solution under ultrasonic irradiation was investigated by gas chromatography-mass spectrometry (GC-MS). The mechanisms of phase formation and morphology control of CdS/ZnS/In₂S₃ microspheres are proposed and discussed in detail. Furthermore, the photocatalytic activity of CdS/ZnS/In₂S ₃ for water splitting was investigated under visible-light irradiation (λ > 400 nm) and an especially high photocatalytic activity (apparent yield is 40.9% at 420 nm) was achieved in the absence of co-catalysts.