Construction of S-scheme heterojunction of OVs-BiOIO3/N-CQDs/g-C3N4 for degradation of tetracycline

The proposal of S-scheme heterojunction reveals the principle of a new photocatalysis mechanism, which is superior to the effect of traditional heterojunction, and provides a strong guarantee for the development of photocatalysis technology. In this work, BiOIO3 rich in oxygen vacancies was obtained by a simple calcination method, and then N-CQDs were anchored to the surface of OVs-BiOIO3 to obtain OVs-BiOIO3/N-CQDs composites. The prepared OVs-BiOIO3/N-CQDs and the band gap structure matched g-C3N4 were constructed to form a N-CQDs mediated S-scheme heterostructure, and finally the OVs-BiOIO3/N-CQDs/g-C3N4 ternary composite was obtained. The structure, morphology and photocatalytic efficiency of the composite were obtained by a series of characterization such as SEM, TEM, XRD, FT -IR, PL, EIS, etc. The results show that, when the reaction conditions is 150 degrees C and 8 h, the catalyst OVs-BiOIO3/N-CQDs/g-C3N4 has the best degradation of 70.5%, which is 1.55 times and 1.24 times OVs-BiOIO3 (45.6%) and g-C3N4 (56.7%) respectively. The results of reactive species trapping experiment showed that center dot O2 ,center dot OH play a major role in the photocatalytic process. Conclusively, the mechanism of N-CQDs mediated S-scheme heterojunction is proposed by analyzing all the results.