A novel 3D/3D S-scheme ZnSe/NiMoO4 heterostructure with significantly enhanced photocatalytic elimination efficiency for tetracycline from actual pharmaceutical wastewater.

The development of highly efficient and stable photocatalysts for removing antibiotic contaminants is of great practical significance for environmental remediation but is also challenging. In this work, a series of novel 3D/3D S-scheme ZnSe/NiMoO4 heterostructure was conveniently synthesized by hydrothermal procedure for the first time. SEM surface morphology characterization revealed that in the optimized 15%ZnSe/NiMoO4 heterostructure, ZnSe presented microsphere shape with average diameter of 2 μm and NiMoO4 had a clear rod-shaped structure with a random distribution length from 5 to 20 μm and width from 100 to 400 nm. The optimized 15%ZnSe/NiMoO4 heterostructure showed tremendous potential for organic contaminants treatment in various aqueous solutions and could degrade 89% and 77% of tetracycline in distilled water and actual pharmaceutical wastewater within 240 min, respectively. In comparison with the degradation efficiency in deionized water, it was almost four and two times higher than pristine NiMoO4 and ZnSe, respectively. To better understand the charge separation and migration in ZnSe/NiMoO4 system, the electrochemical performance of 15%ZnSe/NiMoO4 was detected through transient photocurrent and electrochemical impedance spectroscopy. Results showed that 15%ZnSe/NiMoO4 displayed improved charge separation and migration ability in comparison with pure ZnSe and NiMoO4. Moreover, the photoluminescence spectra of 15%ZnSe/NiMoO4 heterostructure exhibited low intensity because of the suppression of charge recombination. Furthermore, the as-prepared 15%ZnSe/NiMoO4 heterostructure displayed excellent long-term stability and the catalyst could still achieve pollutant degradation of 82% after five recycles. This study affords the guidance to develop NiMoO4-based heterojunctions with enormous potential for the wastewater treatment.