Constructing self-assembled microtubular structured Zn-In-S and modulation mechanism towards efficient photocatalytic degradation of tetracycline

The accumulation of antibiotics in the environment has caused worldwide concern and photocatalytic processes have shown attractive prospects for the elimination of antibiotics due to its sustainability, cleanliness and efficiency. In this study, a series of self-assembled hollow tubular Zn-In-S photocatalysts (Zn-doped In2S3, ZnIn2S4, and ZnS/ZnIn2S4) were first designed by one-step sulfidation of Zn/In-MOFs. The as-synthesized microtubular structured Zn-In-S exhibited high surface area(107.61-127.26 m2/g), high porosity(0.25-0.52 cm3 g-1) and high degradation rate(>= 86%) towards tetracycline within 120 min. Moreover, the photoelectric properties and photocatalytic performance were dependent on the existence of Zn species. Particularly, the optimized hollow microtubular ZnS/ZnIn2S4 composites exhibited ultrahigh photocatalytic degradation rate (>90%) within 1 h solar light irradiation. The kinetic constant reached 0.0379 min-1, which was 2.96, 2.02, and 5.65 times higher than In2S3, ZnIn2S4, and ZnS respectively. The ultrahigh photocatalytic degradation efficiency originated from the formation of direct Z scheme heterojunction between ZnIn2S4 and ZnS. The unique heterojunction enabled the effective separation of electron-hole pairs and the production of highly reactive oxidants (center dot OH, center dot O2-, h+). Density functional theory(DFT) demonstrated a higher charge density near the Fermi level and higher affinity towards O2 molecules, which contributed to the efficient interfacial charge mobility and O2 activation. The work provides guidance for the modulation of ternary catalysts to maximize the virtues of photocatalytic activity.