Titanium(IV) Dioxide Surface‐Modified with Iron Oxide as a Visible Light Photocatalyst

Abstract

The light fandango: Anatase and anatase–rutile composite TiO2 has been modified electronically with highly dispersed surface iron oxide species. The chemisorption–calcination cycle technique was used with [Fe(acac)3] as a precursor (acac=acetylacetonate), leading to pronounced visible‐light activity and a concomitant increase in activity under illumination with UV light (cb=conduction band, vb=valence band).

Comparative study on visible light photocatalytic activity of Fe-modified TiO₂ powders

“…2 is that from the sample mesh used for this observation. Nevertheless, we were unable to identify the Fe-clusters clearly on the TiO 2 surface modified by CCC, as was done in a previous study by Tada et al, 19) probably because of the extremely small size. These results imply that the Fe-cluster size and morphology differ between CCC and MCG.…”

“…6) shows its decrease concomitantly with increasing surface Fe concentration for C1 and C2 samples, which corresponds to a band-gap decrease with surface modification. This trend is obtainable from both anatase and rutile, suggesting effective mixing between the surface Fe(III) levels and O2p by formation of a TiOFe interfacial bond yielding a surface d sub-band, which disperses around the energy level to overlap with the VB of TiO 2 proposed by Tada et al 19) However, such a VB top change was not detected in M1 and M2 samples. The new absorption by Fe modification for these samples can be attributed to the IFCT from the VB of TiO 2 to the Fe(III) ions.…”

“…19) They used P-25 (anatase/rutile = 4/1 w/w) as a TiO 2 source, and proposed that electronic excitation from the surface d sub-band, yielded by mixing between the surface Fe(III) levels and O2p by the TiO Fe interfacial bond to CB of TiO 2 , plays an important role for visible light photocatalytic activity. Although both cases used Fe as a modification element and suggested Fe-cluster formation on the surface of TiO 2 , different mechanisms were proposed.…”

“…These investigations were conducted using different TiO 2 sources and modification processes. For this study, we prepared Femodified TiO 2 using MCG and CCC following procedures described in previous reports 18), 19) using the same TiO 2 powder. Then, photocatalytic decomposition activity was evaluated using gaseous 2-propanol (IPA) under visible light.…”

Synergistic effect between TiO₂ and ubiquitous metal oxides on photocatalytic activity of composite nanostructures

“…On the other hand, the high density of foreign atoms in the host lattice introduces structural imperfections and simultaneously leads to the formation of excessive number of recombination centers that in turn reduce the photocatalytic activity of the material. 9) An alternative approach to induce Vis response in TiO 2 by surface modification with dispersed metal oxide nanoclusters has been recently theoretically described by Nolan 10),11) and demonstrated experimentally by Libera et al 12) and Tada et al 13), 14) According to theoretical calculations of Nolan, 10),11) the altering of TiO 2 surface with nanoclusters of certain metal oxides can induce an upward shift of the valence band (VB) of TiO 2 without affecting the conduction band. The calculations predict the upward shift of the VB near TiO 2 surface on 0.3, 0.4 and 0.6 eV by low valence FeO x , CrO 2 and MoO 2 clusters, respectively.…”