Abstract
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•BiOBr/CDs/g-C3N4 Z-scheme photocatalysts with CDs as solid-state electron mediators were designed.•CDs broaden solar light harvesting and promote the separation of the photogenerated charge carriers.•BiOBr/CDs/g-C3N4 composite exhibits excellent photocatalytic efficiency under visible and near-infrared light.•The composite shows remarkable interfacial charge transfer abilities and a large interface contact area.•The photocatalytic enhancement mechanism for degradation CIP is discussed.
Rapid recombination of photogenerated carriers and narrow visible light absorption range are two main defects in graphitic carbon nitride (g-C3N4)-based photocatalysts. To address these problems, construction of Z-scheme 2D/2D BiOBr/CDs/g-C3N4 heterojunction photocatalysts with carbon dots as solid-state electron mediators has been investigated. The resultant BiOBr/CDs/g-C3N4 hybrids exhibits remarkable interfacial charge transfer abilities and a broadened solar light absorption range owing to the short charge transport distance and the up-converted photoluminescence character of CDs. Simultaneously, the enhanced specific surface area and nanosheet structure impart more active sites to BiOBr/CDs/g-C3N4 composites. As a result, BiOBr/CDs/g-C3N4 composites reveal significant enhancement in the activity of photodegradation of ciprofloxacin (CIP) and tetracycline (TC) under visible and near infrared (NIR) light irradiation. Moreover, the photodegradation efficiency of BiOBr/CDs/g-C3N4 hybrids was significantly enhanced over that of pristine BiOBr nanosheets and g-C3N4 ultrathin nanosheets. The photocatalytic mechanism is expounded according to free radical capture experiments and electron spin resonance spin-trapping tests and the photodegradation intermediates of CIP were detected by liquid chromatography–mass/mass spectrometry. Moreover, BiOBr/CDs/g-C3N4 composites show excellent photostability and reusability after four runs for CIP degradation.