Fabrication of MXene-derived TiO2/Ti3C2 integrated with a ZnS heterostructure and their synergistic effect on the enhanced photocatalytic degradation of tetracycline

Developing innovative photocatalysts for the efficient degradation of pharmaceutical pollutants is crucial in environmental remediation. In this study, we investigate the synthesis of TiO2 nanosheets derived from MXene, specifically integrated onto highly conductive Ti3C2 MXene, and subsequently combined with zinc sulfide (ZnS) to form a heterojunction. This integration process is accomplished using a hydrothermal approach followed by a self-assembly method. We aim to assess the effectiveness of this integrated system in enhancing the photocatalytic degradation of tetracycline (TC). TiO2/Ti3C2 (TT) synthesized in situ exhibits high-energy lattice facets (001) of TiO2 nanosheets, thereby contributing to an exclusive heterojunction within the TiO2/Ti3C2/ZnS (ZTT) heterostructure. The loading of ZnS nanoparticles significantly increases the surface area with a narrow band gap, enhancing the potential for light emission within the visible region. Consequently, ZnS synergistically affects the ZTTx (where x = wt% of ZnS on TT) heterostructure matrix, notably promoting the separation and transfer abilities of the photogenerated carriers. The ZTT5 heterostructure exhibits remarkable adsorption and photoreduction efficiencies, achieving a 97.1% TC removal in 60 min under UV light. Moreover, under simulated solar light, the ZTT5 heterostructure exhibits an impressive TC removal rate of ∼93.8% in 90 min. These results highlight the effective performance of the ZTT5 heterojunction catalyst in facilitating photogenerated charge carriers, leading to improved photocatalytic capabilities. Furthermore, the band structure and density of states of TiO2 (101), Ti3C2 (002), and ZnS (111) were investigated using density functional theory. In addition, a photoreduction mechanism was proposed for TC, involving the transfer of electrons from TiO2 to the MXene surface. After the transfer, the electrons react with O2 to generate •O2−, attributed to the high electron mobility of MXene. The results of this study emphasize the significant potential of the ZTT5 heterostructure for efficiently degrading pharmaceutical pollutants from wastewater.