LaVO4/Bi2O2S S-Scheme Heterojunction Driving Highly Efficient Photocatalytic Degradation of Tetracycline Antibiotics

The rational design and fabrication of semiconductor photocatalysts possessing high intrinsic activity are pivotal for the remediation of tetracycline (TC)-contaminated aqueous streams. Herein, we synthesized a LaVO4/Bi2O2S heterostructure and comprehensively interrogated its physicochemical attributes through a synergistic suite of techniques—X-ray diffraction (XRD), N2 adsorption/desorption isotherms, Fourier-transform infrared spectroscopy (FT-IR), UV–Vis diffuse reflectance spectroscopy (UV-Vis DRS), field-emission scanning and transmission electron microscopy (FE-SEM/TEM), X-ray photoelectron spectroscopy (XPS), steady-state photoluminescence (PL), and photoelectrochemical measurements. These analyses collectively revealed that the LVO/BOS composite with an equal mass ratio of LaVO4 and Bi2O2S manifested pronounced visible-light harvesting, markedly suppressed charge-carrier recombination, and accelerated interfacial charge transfer, as evidenced by enhanced photocurrent response and reduced PL intensity relative to the constituent LaVO4 and Bi2O2S phases. Consequently, under simulated solar irradiation, LVO/BOS achieved a TC degradation efficiency of ≈89% within 90 min, outperforming bare LaVO4 (41%) and Bi2O2S (44%). The corresponding apparent first-order rate constant (k ≈ 0.0214 min−1) exceeded those of LaVO4 (0.0031 min−1) and Bi2O2S (0.0053 min−1) by factors of 6.90 and 4.04, respectively. Radical-scavenging assays coupled with electron-spin-resonance (ESR) spectroscopy identified superoxide (•O2−) as the dominant reactive oxygen species driving TC mineralization. Guided by the experimentally determined band alignments and the observed preferential preservation of high-potential holes in LaVO4 and high-energy electrons in Bi2O2S, an S-scheme (step-scheme) heterojunction mechanism was postulated to rationalize the superior photocatalytic performance. This work underscores the strategic merit of S-scheme LaVO4/Bi2O2S heterostructures as robust, visible-light-driven platforms for the abatement of refractory organic pollutants.