An efficient photo-Fenton In2O3@FeIn2S4 composite catalyst for tetracycline degradation

Photo-Fenton technology has been widely used as an efficient and environmentally friendly method for pollutant degradation. Herein, novel In2O3@FeIn2S4 microflowers are prepared by a two-step hydrothermal method and used as the photo-Fenton catalyst for tetracycline (TC) degradation. Under illumination (lambda > 420 nm), the In2O3@FeIn2S4-0.5 (molar mass ratio of FeIn2S4 to In2O3 is 0.5) shows a higher removal efficiency of TC (98.3 %) in 75 min, than pure In2O3 (60.8 %) and FeIn2S4 (65.8 %). The degradation rate constant of In2O3@FeIn2S4-0.5 for TC is about 5.1 and 3.2 times compared to that of In2O3 and FeIn2S4. In addition, the TC removal efficiency only dropped by 6.7 % after 5 cycles, indicating the superior stability of In2O3@FeIn2S4-0.5. Superoxide radical (center dot O-2(-)), hydroxide radical (center dot OH), and singlet oxygen (O-1(2)) play a crucial role in TC degradation process, while photogenerated holes (h(+)) only play a minor role. The improved performance of In2O3@FeIn2S4 photo-Fenton catalyst could be described as the following: the porous In2O3 microflower supporter extends the reactive interface of FeIn2S4; FeIn2S4 effectively enhances optical absorption ability in the visible range; 2D-2D tight interface formed between In2O3 and FeIn2S4 helps to accelerate the charge transfer; the formation of S-scheme heterostructures improves the parting ability of the photoproduced carriers.