Fabrication of water-floating litchi-like polystyrene-sphere-supported TiO 2 /Bi 2 O 3 S-scheme heterojunction for efficient photocatalytic degradation of tetracycline.

The exploration of advanced photocatalysts for antibiotic degradation is critical, but it remains a challenge due to the lack of rational structural design and in-depth insights into molecular oxygen activation. Water-floating photocatalysts could be one of the best choices owing to their technical features in terms of reasonability and efficiency involving a high oxygenation of photocatalyst surface, fully solar irradiation, and simple recycling and reuse. Herein, a floatable litchi-like architecture of a polystyrene-sphere-supported TiO 2 /Bi 2 O 3 (PS@TiO 2 /Bi 2 O 3 ) S-scheme heterojunction was skillfully constructed and evaluated for photodegradation of model tetracycline (TC) antibiotics. By integrating the advantages of floatability and S-scheme, the TC removal rate of the optimal PS@TiO 2 /Bi 2 O 3 -0.4 catalyst can reach 88.4% under 1 h illumination, which is higher than that of pristine Bi 2 O 3 (60.8%) and PS@TiO 2 (40.1%). Moreover, PS@TiO 2 /Bi 2 O 3 -0.4 exhibits high recyclability and stability, and there is no significant loss of activity after five cycles of repeated use. With the aid of liquid chromatography-mass spectrometry analysis and density functional theory calculations, a reasonable degradation pathway for TC was proposed. The present work provides a recyclable and efficient approach for the photodegradation of TC, expecting to guide the innovative exploitation of other environmental systems.