Z-scheme heterojunction Bi2MoO6/NH2-UiO-66(Zr/Ce) for efficient photocatalytic degradation of oxytetracycline: Pathways and mechanism

Abstract

In this study, Bi2MoO6/NH2-UiO-66(Zr/Ce) photocatalytic materials with heterojunction structure were synthesized by the hydrothermal method, and their photocatalytic degradation of oxytetracycline was researched. All of the composites exhibited better photocatalytic degradation properties than the pristine component. BMNU-2 showed the optimal photodegradation efficiency of 93.7 % after 150 min illumination, with the kinetic constant 7.22 and 3.37 times higher than that of NH2-UiO-66(Zr/Ce) and Bi2MoO6, respectively. The intermediates and degradation pathways of oxytetracycline were investigated by combining intermediate products testing and theoretical calculations. The ·O2–, h+ and ·OH are all the vital active species, and the degradation mechanism of oxytetracycline have been thoroughly investigated based on energy band theory. The toxicity test was conducted to investigate the environmental effect of OTC and the intermediates. The outstanding photocatalytic efficiency is mainly owing to three reasons: (1) The introduction of Ce in mixed-metal MOFs minished the band gap of the MOFs; (2) The Ce4+/Ce3+ cycle improved the charge separation efficiency; (3) The formation of heterojunction accelerated the charge transfer and expanded the extension of light absorption. This research offers neoteric thinking for the design of high-performance photocatalytic materials.