Selective efficient photocatalytic degradation of antibiotics and direct Z-type migration pathway for hierarchical core–shell TiO 2 /g-C 3 N 4 composites

Constructing superior Z-type photocatalytic heterojunction is beneficial to effectively enlarge interface contact, improve the photo-generated carrier separation rate, and retain the high redox ability. In this work, we designed a hierarchical core–shell g-C 3 N 4 /TiO 2 structure to build Z-type heterojunction via combining simple template method and pyrolysis process. A close-knit Z-type heterojunction was constructed using TiO 2 as a thick core and g-C 3 N 4 as an ultra-thin shell. The effects of lamp source, wavelength, tetracycline (TC) concentration, and photocatalyst dose on the degradation performance on TC of g-C 3 N 4 /TiO 2 were inspected. 0.1TiO 2 /g-C 3 N 4 photocatalyst had the best degradation rate and highest removal rate within 30 min, and its degradation rate was about 49, 23, and 5 times than pure g-C 3 N 4 , TiO 2 , and commercial TiO 2 /g-C 3 N 4 in respect. Moreover, compared with degradation ability under Xenon lamp, LED irradiation for g-C 3 N 4 /TiO 2 composites showed a remarkable selective degradation. The fast and efficient Z-type transfer pathway of 0.1 g-C 3 N 4 /TiO 2 was realized by forming an optimized interface and abundant surface active sites ascribed to the combined action of thick TiO 2 core and ultra-thin g-C 3 N 4 shell. In addition, the degradation intermediates were analyzed by LC–MS and suggested pathways of degradation. The work could provide novel design concept to obtain reliable Z-type photocatalysts with hierarchical core–shell structure applied in degradation of antibiotic wastewater.