In this study, the S-scheme heterostructure photocatalyst of SnS2/TiO2 (denoted as ST) ultrathin nanosheet-nanorod arrays with high efficiency for the degradation of tetracycline hydrochloride (TC-HCl) was successfully prepared by a two-step hydrothermal method. By expanding the light absorption area and hindering the reorganization of light-generated e--h+ pairs, the binding of TiO2 to SnS2 prepared photocatalysts with highly efficient photocatalytic activity and long-term stability. The results showed that the optimized photocatalyst samples all contributed to the degradation efficiency of tetracycline hydrochloride within 90 min than the photocatalytic degradation of pure TiO2 (41.1%). Among them, the ST loaded with 30 mM SnS2 exhibited the highest photocatalytic degradation efficiency of TC-HCl (93.4%). The reaction rate constant K is 0.02597 min-1, and the transient photocurrent density of ST-30 was up to 34.35 A/cm2, which were 5.78 and 10.54 times higher than that of unmodified TiO2. At the same time, the effects of photocatalysts on the degradation efficiency of TC-HCl under different conditions (pH values, inorganic anions and antibiotic concentrations) were systematically investigated. The inhibition of the degradation efficiency of tetracycline hydrochloride by SnS2/TiO2 heterojunction with the addition of different free radical scavengers indicated that ·O2- and ·OH were the main active substances involved in the degradation process. In addition, two environmentally friendly degradation pathways were proposed based on the analysis of liquid chromatography-mass spectrometry (LC-MS) results and the toxicity assessment of various intermediates in the degradation process. Finally, the photocatalytic mechanism of SnS2/TiO2 heterojunctions was proposed based on the optical and electrochemical properties of the photocatalysts as shown in the tests. These results indicate that the synthesized S-scheme heterostructure photocatalyst SnS2/TiO2 can significantly improve the light trapping ability and reduce the photoelectron-hole complexation rate, which is a promising approach to enhance the degradation efficiency of photocatalysts.
Aiguo Han,Mei Li,Shengbo Zhang,Xinli Zhu,Jinyu Han,Qingfeng Ge,Hua Wang
In recent years, defective TiO2-based composite nanomaterials have received much attention in the field of photocatalysis. In this work, TiB2was used as a precursor to successfully prepare Ti3+defective TiO2(TiO2-B) with a truncated bipyramidal structure by a one-step method. Then, the SnS2nanosheets were assembled onto the as-prepared TiO2-B through simple hydrothermal reaction. TiO2-B exhibits strong visible light absorption properties, but the recombination rate of the photo-generated electron-hole pair was high and does not exhibit ideal photocatalytic performance. Upon introducing SnS2, the heterojunction catalyst SnS2-Ti3+defective TiO2(SnS2/TiO2-B) not only possesses the strong light absorption from UV to visible light region, the lowest photo-generated charge recombination rate but also achieves a more negative conduction band potential than the reduction potential of CO2to CO, and thereby, exhibits the significantly enhanced selectivity and yield of CO in photocatalytic CO2reduction. Notably, SnS2/TiO2-B produces CO at a rate of 58 µmol·h−1·g−1with CO selectivity of 96.3% under visible light irradiation, which is 2 and 19 times greater than those of alone TiO2-B and SnS2, respectively. Finally, a plausible photocatalytic mechanism on SnS2/TiO2-B was proposed that the electron transfer between TiO2and SnS2follows the Z-scheme mode. Our results present an effective way to gain highly efficient TiO2based photocatalysts for CO2reduction by combining different modification methods of TiO2and make full use of the synergistic effects.Keywords:photocatalytic CO2reduction;TiO2nanoplates;SnS2nanosheets;Ti3+defective TiO2
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