Preparation And Photocatalytic Properties Of BiFeO₃/graphene Nanocomposites

Graphene-based visible light photocatalyst has been actively pursued in therecent years due to the high charge mobility of graphene and hence lowerrecombination rate of electron/hole pairs. BiFeO₃with a band gap in the visible rangeis considered promising candidate as oxide photocatalyst.BiFeO₃-Graphene nanohybridsare fabricated via a facile hydrothermal treatment.The modulations of both morphology and band structure of BiFeO₃by graphene areinvestigated by XRD, SEM and diffuse reflectance spectra. Nanohybrids with BiFeO₃nanocrystallines of¹00nm in diameter uniformly decorated on graphene nanosheetsare successfully synthesized, which exhibit band gap of about1.78eV. Chemicalbondings between BiFeO₃and graphene are characterized by XPS analysis to provethe existence of Fe－O－C bonding. The rate for the photo-degradation of CongoRed under visible lights is six times that for the BiFeO₃particles, which is attributedto the combined effects of modulated band gap and covalent bonding between BiFeO₃and graphene.Additionaly, the effects of KOH concentration on the crystallization andphotocatalytic performance of the composites are investigated by varying theconcentration from1M to14M in the hydrothermal process. The KOH concentrationwill greatly influence the purity, morphology and particle size of BiFeO₃. It alsoinfluences the regraphitization of graphene oxide, resulting in the poor compostioncoupling between BiFeO₃and graphene.Finally, formation mechanism of the nanocomposites is proposed. The growth ofBiFeO₃depends both on the reduction and regraphitization process of graphene oxideand on the type of grow units, resulting from the concentration of KOH.