Enhanced in-situ oxygen evolution and hydrogen peroxide production by a floatable ZnO-incorporated polyurethane photocatalyst for sulfamethoxazole degradation

A highly efficient rigid floatable photocatalyst was prepared by seeding ZnO in polyurethane (PU) and subse-quent hydrothermal ZnO coating (P-ZsZc). Compared to pristine ZnO, granular P-ZsZc had an uplifted valence band (VB) and generated new covalent Zn-O-C bond between PU and ZnO, resulting in a significantly enhanced photocorrosion resistance by boosting the mobility of photoexcited holes. In addition, the VB of P-ZsZc was favorable for the in-situ oxygen evolution reaction (OER) and H2O2 production. As a result, the P-ZsZc achieved -98% removal of sulfamethoxazole (SMX) within 2 h for 5 consecutive cycles. Moreover, the SMX removal rate and Zn(II) leaching remained at -0.036 min-1 and 0.17 mg L-1, respectively, even during the fifth cycle for 10 h. Furthermore, scavenger experiments and electron spin resonance (ESR) spin trap analysis revealed that the main photogenerated reactive oxygen species (ROS) was H2O2. Floatable P-ZsZc showed constant SMX removal of -90% in continuous flow experiments (CFEs) for up to 10 h of operation. This study offers a new approach to prepare floatable rigid photocatalysts capable of in-situ oxygen and H2O2 production to degrade organic pollutants.