Determination of the roles of FeIII in the interface between titanium dioxide and montmorillonite in FeIII-doped montmorillonite/titanium dioxide composites as photocatalysts

Abstract

Fe/Mt./TiO2 with FeIII cation doped on montmorillonite (Mt) and, Mt./Fe-TiO2 with FeIII cation doped on TiO2 were synthesized at three temperatures. Compared with the influence from the position of FeIII, the synthesis temperature had moderate interference on the TiO2 formation as was implied by X-ray fluorescence (XRF) and X-ray diffraction (XRD). Characterizations of diffuse reflectance UV–vis spectroscopy (DRS), photoluminescence spectroscopy (PL), photocurrent, and electrochemical impedance spectroscopy (EIS) indicated the more excellent photocatalytic property of Fe/Mt./TiO2 composite than Mt./Fe-TiO2 composite. The energy-resolved distribution of electron traps (ERDT) pattern revealed a distinguished phase composing from the surface to the bulk for both Fe/Mt./TiO2 and Mt./Fe-TiO2 and demonstrated almost the same photocatalytic property of the TiO2 particle surface on both Fe/Mt./TiO2 and Mt./Fe-TiO2. The photocatalytic activities test for phenol decomposition on Fe/Mt./TiO2 was better than Mt./Fe-TiO2 which is consistent with the DRS, PL, photocurrent, and EIS results. A heterojunction between the Mt. and TiO2 in Fe/Mt./TiO2 was proposed to explain the inconsistency of the photocatalytic property and photocatalytic performance for the two composites and the consistency of the photocatalytic property for the surface of TiO2 particles on the composites. To increase the photocatalytic activity of Fe/Mt./TiO2, the electron at the Fermi level on FeIII-doped Mt. may be coupled with the hole on the valance band of TiO2, resulting in effective separation of electron and hole and reduction and/or avoidance of recombination.