High-performance photocatalytic decomposition of PFOA by BiOX/TiO2 heterojunctions: Self-induced inner electric fields and band alignment

BiOX (X = Cl, Br and I) and BiOX/TiO2 photocatalysts were prepared by a facile hydrothermal approach. The BiOX/TiO2 heterojunctions demonstrated significantly enhanced efficiency for photocatalytic decomposition of perfluorooctanoic acid (PFOA) compared with sole BiOX or TiO2. PFOA (10 mg L-1) was completely degraded by BiOCl(Br)/TiO2 in 8 h. Moreover, BiOCl/TiO2 attained deep decomposition of PFOA with a high defluorination ratio of 82%. The p-n heterojunctions between BiOX and TiO2 were confirmed by a series of characterizations. The photo-induced holes would migrate from the valance band (VB) of TiO2 to BiOX, driven by the built-in electric field (BIEF) near the interfaces of p-n heterojunctions, the inner electric fields (IEF) in BiOX and the higher VB position of BiOX. The X-ray diffraction (XRD) and TEM characterizations indicated that TiO2 combined with BiOX along the left perpendicular110right perpendicular facet, which facilitated photo-induced electron transfer in the left perpendicular001right perpendicular direction, thus benefiting PFOA decomposition.

Automated summary

BiOX/TiO2 photocatalysts prepared by hydrothermal method showed enhanced efficiency in photocatalytic decomposition of PFOA compared to sole BiOX or TiO2. The formation of p-n heterojunctions and the driving force of internal electric fields enabled the migration of photo-induced holes from TiO2 to BiOX, facilitating PFOA decomposition.