The precursors’ feeding ratio of NCQDs/NaBiO3·2H2O induced the modulation of hydrothermal reaction products and their photocatalytic properties

Regulating the composition and proportion of heterojunctions is critical to improve their photocatalytic properties. Many bismuth-based oxides are readily converted from one oxide to another under certain conditions, which supplies a simple strategy for the in-situ construction of bismuth-based oxides heterostructures with controllable composition and proportion. Herein, a series of tunable products from NCQDs/Bi2O4 composite (NCQDs: nitrogen-doped carbon quantum dots) to Bi2O4/Bi2O2CO3 heterojunction to pure Bi2O2CO3 were obtained just by adjusting the NCQDs/NaBiO3·2H2O precursors’ feeding ratio during the hydrothermal process, in which NCQDs act as an active component or carbon source dependant on the feeding ratio. Both NCQDs/Bi2O4 and Bi2O4/Bi2O2CO3 heterostructures exhibit enhanced photocatalytic efficiency for removing methyl orange (MO) and bisphenol A (BPA) under simulated sunlight, compared with Bi2O4 alone. Nevertheless, the latter is more effective in promoting the catalytic activity of Bi2O4 than the former. The reaction rate constant k of the optimal NCQDs/Bi2O4 hybrid is only 1.6 and 2.37 times higher than that of single Bi2O4, whereas the k of the optimal Bi2O4/Bi2O2CO3 heterojunction is about 2.93 and 3.07 times higher than that of single Bi2O4 for the degradation of MO and BPA, respectively. The much higher photoinduced charges’ separation efficiency, verified by the transient photocurrent response and EIS results, should be the main reason the Bi2O4/Bi2O2CO3 heterojunction possesses superior photocatalytic activity to the NCQDs/Bi2O4 heterostructure. Hole (h+) and superoxide radical (•O2−) are determined to be the primary and secondary important active species for the photodegradation reaction, respectively. This work supplies a convenient strategy to modulate the composition and proportion of the hydrothermal reaction products and their photocatalytic properties through changing the precursors’ feeding ratio of NCQDs/NaBiO3·2H2O.