Effect of different carbon dots positions on the transfer of photo-induced charges in type I heterojunction for significantly enhanced photocatalytic activity

The design of highly efficient photocatalysts is a hot topic in the field of photocatalysis. Herein, two kinds of ternary heterojunctions with coating carbon dots (CDs) on the different positions of ZnFe2O4@ZnIn2S4 heterojunctions (CDs-ZnFe2O4@ZnIn2S4 and ZnFe2O4@ZnIn2S4-CDs) were developed for exploring the role of CDs on charge transfer of heterojunctions. Compared with ZnFe2O4@ZnIn2S4-CDs (CDs are fixed to the exterior of the core–shell structure), CDs-ZnFe2O4@ZnIn2S4 (CDs are fixed to the interior of the core–shell structure) exhibits a more efficient acceleration of migration and separation of photo-induced charges. As expected, the optimal CDs-ZnFe2O4@ZnIn2S4 sample exhibits the optimized tetracycline (TC, 30 mg/L) degradation rate of 87.3 % in 120 min under visible light irradiation. This work reveals that CDs existing at the contact interface of heterojunction establish smooth and fast channels for electron transport, accelerate electron transport and prevent the recombination of electron-hole pairs, thus significantly improving the photocatalytic performance of type-I heterojunction constructed by ZnFe2O4 and ZnIn2S4.