Hydrothermal synthesis of Bi2WO6/Bi2O4 heterojunction with WO3 and NaBiO3·2 H2O powders as precursors to improve visible light photocatalytic degradation performance

Abstract

The limited visible light response range and fast recombination rate of photoinduced carriers restrict the photocatalytic performance of Bi2WO6. Herein, a novel low temperature hydrothermal approach was developed to construct the Bi2WO6/Bi2O4 heterojunction with WO3 and NaBiO3•2 H2O powders as precursors and the latter as the only bismuth source. During the hydrothermal reaction, WO3 first reacts with NaBiO3·2 H2O to generate Bi2WO6 and then the residual NaBiO3·2 H2O converts into Bi2O4, in-situ forming the Bi2WO6/Bi2O4 heterojunction with the co-shared Bi atoms. The content of Bi2WO6 in the heterostructure can be facilely modulated by changing the amount of WO3 added. The construction of Bi2WO6/Bi2O4 heterojunction could not only extend the spectral response range but also improve the separation efficiency of photoinduced charges. Consequently, the photocatalytic degradation performance to tetracycline (phenol) for the optimal Bi2WO6/Bi2O4 heterostructure is 5.19 and 1.77 times (4.75 and 1.66 times) higher than that of single Bi2WO6 and Bi2O4 under visible light, respectively. The capture experiments of active species and electron spin resonance spectra demonstrate that radicals (·O2-) and holes (h+) are the first and second important active species, respectively, during the catalytic degradation. Our work provides a new idea for the fabrication of high-performance Bi2WO6-based junction photocatalysts.