A novel Z-scheme SnS/NiAl-LDH/g-C3N4 heterojunction for piezo-photocatalytic degradation of tetracycline: Performance and mechanism

The construction of a heterojunction piezo-photocatalyst is one of the most effective strategies to accelerate charge transfer and improve catalytic performance. A novel ternary heterojunction was synthesized by introducing SnS nanoparticles (NPs) onto the surface of a NiAl-LDH/g-C3N4 (LDH/CN) nanosheets via a facile hydrothermal method. The separation and transfer paths of carriers was studied for the piezo-photocatalytic degradation of tetracycline (TC), a common antibiotic, under ultrasonic and visible light irradiation. The SnS/LDH/CN piezo-photocatalyst generated a built-in electric field by the piezoelectric effect, which was beneficial for the separation of electron-hole pairs. Furthermore, the Z-scheme heterojunction endowed with a larger surface area, abundant active sites, and improved light-harvesting capacity further improved piezo-photocatalytic performance for TC. In particular, a CLS-30 (30 wt% of SnS on LDH/CN) heterojunction exhibited the highest degradation efficiency with 98.5 % removal of TC (20 mg/L) in 60 min, which was higher than that of ultrasonic vibration (38.2 %) and visible light illumination (79.4 %). TC degradation efficiency remained at almost 90 % after 4 consecutive cycles. This work provides a novel viewpoint for designing high-performance and stable heterojunction piezo-photocatalysts for energy limited wastewater remediation applications.