The precursors' feeding ratio of NCQDs/NaBiO3middot2H2O 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 het-erostructures with controllable composition and proportion. Herein, a series of tunable products from NCQDs/Bi2O4 composite (NCQDs: nitrogen-doped carbon quantum dots) to Bi2O4/Bi2O2CO3 heterojunc-tion to pure Bi2O2CO3 were obtained just by adjusting the NCQDs/NaBiO3middot2H2O precursors' feeding ratio during the hydrothermal process, in which NCQDs act as an active component or carbon source depen-dant on the feeding ratio. Both NCQDs/Bi2O4 and Bi2O4/Bi2O2CO3 heterostructures exhibit enhanced pho-tocatalytic 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 hetero-junction 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 (center dot O2 -) are determined to be the primary and secondary important active species for the pho-todegradation reaction, respectively. This work supplies a convenient strategy to modulate the composi-tion and proportion of the hydrothermal reaction products and their photocatalytic properties through changing the precursors' feeding ratio of NCQDs/NaBiO3middot2H2O.(c) 2023 Elsevier B.V. All rights reserved.