α-Bi2O3/Bi2O2CO3/g-C3N4 ternary double type II heterojunction was obtained through twice in-situ growth by solvothermal calcination method to improve the photocatalytic degradation of tetracycline

A novel in-situ grown α-Bi 2 O 3 /Bi 2 O 2 CO 3 /g-C 3 N 4 heterojunction (BBCx) was successfully fabricated via a two-step in-situ growth by a simple solvothermal calcination method. In this process, g-C 3 N 4 served as the substrate for the growth of Bi 2 O 2 CO 3 nanoplates, while Bi 2 O 2 CO 3 acted as the substrate for the subsequent growth of α-Bi 2 O 3 nanoplates. By characterizing the nanocomposite using different techniques, it was confirmed that the components of this ternary material are tightly bonded through heterojunction formation. Photocatalytic tests demonstrated that the composite exhibited higher activity than pure α-Bi 2 O 3 , Bi 2 O 2 CO 3 and g-C 3 N 4 . Among the composite materials, BBC400—obtained by solvothermal treatment followed by calcination at 400 °C for 2 h—exhibited the highest degradation efficiency toward tetracycline hydrochloride (TC-HCl), with a removal rate of 70% of TC-HCl within 120 min and a rate constant of 0.0081 min −1 . This rate constant was approximately 16.2 times (0.0005 min −1 ), 1.92 times (0.0042 min −1 ) and 1.35 times (0.006 min −1 ) higher than those of pure Bi 2 O 2 CO 3 , g-C 3 N 4 and α-Bi 2 O 3 , respectively. This synthesis approach offers a new strategy for the in-situ construction of heterojunction nanocomposites.