Hierarchical h-, m- and n-BiPO4 microspheres: facile synthesis and application in the photocatalytic decomposition of refractory phenols and benzene

Abstract

BiPO₄ microspheres with three kinds of crystal phase (h-BiPO₄, m-BiPO₄ and n-BiPO₄) were prepared by a facile hydrothermal-calcination process. The crystalline phase, microstructures and photoelectrochemical properties were studied by various techniques. The results indicated that h-BiPO₄ could transform into m-BiPO₄ at 600 °C. Interestingly, h-BiPO₄ accompanied with a little bit of n-BiPO₄ would transform into n-BiPO₄. After UV irradiation for 2 h, conversion of 94.6% and a mineralization rate of 76.8% could be achieved on n-BiPO₄ for photocatalytic degradation of bisphenol A, which is almost 1.33 times as high as that of m-BiPO₄ and 3.14 times that of h-BiPO₄. Moreover, the n-BiPO₄ also displayed the highest photocatalytic activity for degradation of other phenols (phenol and p-chlorophenol) in water and gaseous benzene. The enhancement of activity could be attributed to the improvement of the photogenerated electron–hole separation efficiency, which would be conducive to the formation of active species (hydroxyl radicals (˙OH) and superoxide radicals (˙O₂⁻)). The results suggest that n-BiPO₄ shows potential applications as an efficient and stable photocatalyst for the photocatalytic decomposition of persistent organic pollutants in water and in the gas phase.