One-step hydrothermal synthesis of visible-light-driven In_2.77S₄/SrCO₃ heterojunction with efficient photocatalytic activity for degradation of methyl orange and tetracycline

The In_2.77S₄/SrCO₃ heterojunction photocatalyst had been prepared by one-step hydrothermal method. X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectrometry, UV-Vis diffuse reflectance spectroscopy and electrochemical impedance spectroscopy were used to analyze the structure, morphology, chemical compositions, optical properties and charge carrier behaviors of the as-prepared In_2.77S₄/SrCO₃ hybrids, respectively. Experimental results revealed the SrCO₃ could obviously improve the recyclability and photocatalytic activities of In_2.77S₄ nanosheets for both methyl orange and tetracycline oxidation under visible light. The photocatalytic degradation efficiency of the as-obtained In_2.77S₄/SrCO₃ hybrids was first increased and then decreased with increasing the molar ratio of Sr(NO₃)₂ to In(NO₃)₃.4.5H₂O. When it was 0.4:1, that of the as-prepared hybrids with the band gap of 1.63 eV reached the maximum of 96.0% in 30 min for methyl orange and 82.7% in 20 min for tetracycline. These were higher than 88.0% and 40.0% of In_2.77S₄ nanosheets as well as 0.8 and 1.8% of SrCO₃ particles, respectively. After three cycles, its photocatalytic efficiency still possessed 92.7% for methyl orange and 80.3% for tetracycline, which were much higher than 35.3% and 11.3% of In_2.77S₄ nanosheets. Moreover, the possible photocatalytic degradation mechanism of the In_2.77S₄/SrCO₃ hybrids was also proposed. (orig.)