Enhanced visible light photocatalytic activity and stability of CQDs/BiOBr composites: The upconversion effect of CQDs

CQDs/BiOBr composites with oxygen vacancies were synthesized by a simple hydrolysis method at room temperature. The obtained composites exhibited much higher photocatalytic activity and stability than pure BiOBr under visible light. The upconversion effect of CQDs on BiOBr was studied by photoluminescence (PL) spectra, transient photocurrent (PC) responses measurements, electron spin resonance (ESR) analysis, reactive species scavenger experiments, and RhB and BPA degradation under monochromatic light irradiation. The results demonstrated that the upconversion effect of CQDs could improve O2− formation on BiOBr during photocatalytic process via more electron transfer in oxygen vacancies owing to the desirable long wavelength visible light and near infrared (NIR) light absorption property of CQDs. Moreover, the upconversion effect of CQDs could refresh the oxygen vacancies on BiOBr and therefore maintain the photocatalytic stability of BiOBr.