The Effect of pH Values on the Synthesis, Microstructure and Photocatalytic Activity of Ce-Bi2O3 by a Two-Step Hydrothermal Method

In this study, the effect of pH values on the microstructure and photocatalytic activity of Ce-Bi2O3 under visible light irradiation was investigated in detail. In alkaline condition (e.g. pH=9), the as-prepared Ce-Bi2O3 exhibited an agglomerated status and mesoporous structures without a long-range order. While in weak acid condition (e.g. pH=5), the Ce-Bi2O3 exhibited a best morphology with irregular nanosheets. Correspondingly, it possessed largest surface area (24.641m(2)g(-1)) and pore volume (9.825E-02cm(3)g(-1)). These unique nanosheets can offer an attachment for pollutant molecules and reduce the distance of electron immigration from inner to surface, thus facilitating the separation of photoelectron and hole pairs. Compared with the pure Bi2O3, the band gap of Ce-Bi2O3 prepared at different pH was much lower. Among them, the band gap of Ce-Bi2O3 (pH of 5) was lowest (2.61 eV). Ce-Bi2O3 (pH of 5) exhibited as tetragonal crystal with the bismuth oxide in the form of the composites, which could reduce the band gap width or suppress the charge-carrier recombination, subsequently possessing great photocatalytic activity for acid orange II under visible light irradiation. After 2h degradation under visible light, the degradation rate of acid Orange II was up to 96.44% by Ce-Bi2O3 prepared at pH 5. Overall, it can be concluded that the pH values had effects on the microstructure and photocatalytic activity of Ce-Bi2O3 catalysts.