Facile preparation of novel Sb2S3 nanoparticles/rod-like α-Ag2WO4 heterojunction photocatalysts: Continuous modulation of band structure towards the efficient removal of organic contaminants

In order to fabricate the recyclable catalyst with enhanced photocatalytic degradation and stability, rod-like alpha-Ag2WO4 (n-type) modified Sb2S3 (p-type) chalcogenide were prepared by wet-impregnation method. The physico-chemical properties were characterized by X-ray diffraction, micro-Raman spectroscopy, UV-vis diffuse reflectance spectroscopy, field emission scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy and Brunauer-Emmett-Teller analysis. UV-vis spectra show the Sb2S3 chalcogenide extends the visible light absorption of the synthesized composites when compared to that of pristine alpha-Ag2WO4. The photocatalytic degradation of prepared samples was investigated by MB, RhB and MO under the visible light irradiation. The highest photocatalytic degradation efficiency (91.23% of MB dye within 60 min) is observed for 25 wt% Sb2S3/alpha-Ag2WO4 nanocomposite when compared to other photocatalysts. The pseudo-first order kinetic rate constant of 25 wt% Sb2S3/alpha-Ag2WO4 (4.20 x 10(-2) min(-1)) photocatalyst is 3.7 and 5.7 times higher than Sb2S3 and alpha-Ag2WO4 respectively. The colorless toxic pollutant tetracycline hydrochloride used as a model pollutant and it under go degradation of 53.06% after 180 min and reaction rate constant is about 4.1 x 10(-3) min(-1) over 25 wt% Sb2S3/alpha-Ag2WO4 photocatalyst. The radical trapping measurement reveals that h(+) and center dot O-2(-) radicals the key reactive species in the suspension of Sb2S3/alpha-Ag2WO4 photocatalyst, which decompose the MB dye efficiently. Moreover, a possible photocatalytic mechanism is proposed based on the trapping results with enhanced photocatalytic activity for the efficient separation of photogenerated e(-)-h(+) pairs, the excellent oxidation and reduction capabilities of the Sb2S3/alpha-Ag2WO4 heterojunction catalysts. The recycling experiments result reveals that Sb2S3/alpha-Ag2WO4 (25 wt%) nano-composite maintained good stability and an active photo catalyst after the five-cycle tests. The present study provides the novel insight into the fabrication of alpha-Ag2WO4 based photocatalysts that improved the visible light photodegradation efficiency of organic contaminants in the industrial wastewater.