Preparation of Binary Type II α-Bi2O3/Bi12TiO20 Cross-Shaped Heterojunction with Enhanced Visible Light Photocatalytic Performance

The binary type II α-Bi2O3/Bi12TiO20 heterojunction composite was successfully obtained by a simple hydrothermal process. The pH value and the Bi/Ti molar ratio were the key to form the α-Bi2O3/Bi12TiO20 heterojunction. The α-Bi2O3 nanobelts intertwined with the Bi12TiO20 nanobelts to form a cross-shaped structure in the composite. The obvious red-shift can be detected in Raman spectra. UV–vis DRS also revealed that the effectively reduced band gap of the heterojunction composite led to sunlight absorption in a larger range. Meanwhile, the photocurrent responses and the EIS demonstrated that the combination of Bi12TiO20 and α-Bi2O3 significantly promoted the separation of photogenerated electron–hole pairs and suppressed their recombination, which was also confirmed by PL analysis. Furthermore, photocatalytic degradation experiments proved that the α-Bi2O3/Bi12TiO20 heterojunction composite had excellent catalytic performance under visible light, whose rate constant value (k) was about 2.0 times that of pure α-Bi2O3 and 4.5 times that of pure Bi12TiO20 samples. A possible photocatalytic mechanism of α-Bi2O3/Bi12TiO20 was also proposed based on p–p and type II heterojunction. It was concluded that the heterojunction structure markedly promoted the migration and separation of carriers to enhance its photoactivity.