Synthesis and enhanced visible light photocatalytic CO2 reduction of BiPO4–BiOBrxI1?x p–n heterojunctions with adjustable energy band

摘要

A series of novel BiPO _(4) –BiOBr _( x ) I _(1? x ) p–n heterojunctions were successfully prepared by a facile solvothermal method. The morphology, structure and optical properties of photocatalysts were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and ultraviolet visible diffuse reflectance spectroscopy. The visible light photocatalytic activities of BiPO _(4) –BiOBr _( x ) I _(1? x ) heterojunctions were investigated by photocatalytically reducing CO _(2) . After 4 hours of irradiation, the 5% BiPO _(4) –BiOBr _(0.75) I _(0.25) heterojunction showed the highest photocatalytic activity with the yields of CO and CH _(4) up to 24.9 and 9.4 μmol g _(cat) ~(?1) respectively. The improved photocatalytic activity may be due to the formation of BiPO _(4) –BiOBr _( x ) I _(1? x ) p–n heterojunctions which can effectively restrict the recombination rate of the photoexcited charge carriers. Moreover, the energy band structure of BiPO _(4) –BiOBr _( x ) I _(1? x ) heterojunctions could be easily adjusted by changing the mole ratio of I and Br. The possible mechanism of the enhancement of the photocatalytic performance was also proposed based on experimental and theoretical analysis. The present study may provide a rational strategy to design highly efficient heterojunctions with an adjustable energy band for environmental treatment and energy conversion.