Partial phase transition induced bidirectional transfer of charge carriers in SrTiO₃:γ/α-Bi₂O₃heterojunction for ultrafast photodegradation of norfloxacin and bisphenol A

The phase transition in heterojunction preparation can greatly change the energy band configuration to tune the separation efficiency of photogenerated charge carriers. In this paper, γ-Bi2O3 partially converted into α-Bi2O3 to form triphase heterostructure SrTiO3:γ/α-Bi2O3 after insitu-growth of γ-Bi2O3 and SrTiO3 heterojunction. The photocatalytic degradation rates of the norfloxacin and the bisphenol A using the optimum sample are 0.13 min-1 and 0.09 min-1, much faster than that of any other catalysts reported previously. In the five cycling tests, the degradation rates of the norfloxacin and the bisphenol A are higher than 0.11 min-1 and 0.08 min-1 while the sample has good structural stability. The ultrafast photodegradation rates come from the partial phase transition inducing double Z-type energy band formation, realizing the bidirectional transfer of charge carriers to accelerate their separation. The SrTiO3 conduction band potential - 1.6 V and γ-/α-Bi2O3 valence band potential 2.3/1.75 V are preserved to generate O2•-, OH•, and hole for photocatalytic degradation. The degradation paths of these two pollutants are given via mass spectrum analysis and the final products are non-toxicity to environment by the growth by the Escherichia coli. The partial phase transition gives a novel idea for the designing of highly active heterojunction catalyst with multidirectional transfer of charge carriers.