Carbon quantum dots in situ coupling to bismuth oxyiodide via reactable ionic liquid with enhanced photocatalytic molecular oxygen activation performance

In this study, carbon quantum dots (CQDs)/bismuth oxyiodide (BiOI) materials have been synthesized via a reactable ionic liquid (IL) 1-hexyl-3-methyl-imidazolium iodine assisted solvothermal method. The introduction of IL was beneficial to construct the tight junctions between CQDs and BiOI. Based on the initial formation of strong-coupling between CQDs and IL, the tight junctions between CQDs and BiOI can be constructed as the iodide ions in the IL react with bismuth nitrate to in situ form BiOI during solvothermal treatment. The photocatalytic activity of the as-prepared CQDs/BiOI materials was evaluated using rhodamine B (RhB) as target pollutant. The CQDs/BiOI materials displayed the enhanced photocatalytic performance than pure BiOI while the 6 wt% CQDs/BiOI materials showed the highest activity. The enhanced photocatalytic activity can be ascribed to the cooperation effect of the excellent contact interface between BiOI and CQDs, while the effective separation of charge carriers via CQDs and the CQDs acted as photocatalytic reaction centers. The main active species during the photodegradation process was determined and photocatalytic mechanism was proposed based on the X-ray photoelectron spectroscopy valence band spectra, active species trapping experiments and electron spin resonance analysis.