TiO2 nanocluster modified-rutile TiO2 photocatalyst: a first principles investigation

Abstract

Access to the full text of the published version may require a subscription. The clusters adsorb strongly at the surface giving adsorption energies from -2.7 eV to -6.7 eV. The resulting structures show a large number of new Ti-O bonds created between the cluster and the surface, so that the new bonds enhance the stability. The electronic density of states (EDOS) shows that the valence band edge is shifted upwards, due to new nanocluster derived states in this region, while the conduction band is unchanged and composed of the Ti 3d states from the surface. This 20 reduces the band gap over bare TiO 2 , potentially shifting light absorption into the visible region. The valence and conduction band composition of these heterostructures will favour spatial separation of electrons and holes after light excitation, thus giving improved photocatalytic properties in these novel structures. Rights © The Royal Society of Chemistry 2013. This is the Accepted Manuscript version of a published work that appeared in final form25

Design of Novel Visible Light Active Photocatalyst Materials: Surface Modified TiO2

“…All adsorption energies are negative, and the magnitudes of the adsorption energies indicate strong binding of the nanocluster at the rutile (110) surface. We further showed that when the nanoclusters are anchored at the surface it is not energetically favourable for them to aggregate into larger structures, which would then kill any advantaged gained by having the TiO2 surface modified with the nanoclusters [79] .…”

“…In a recent paper [79] we examined the energetics of TiO2 cluster aggregation and found that although gas phase cluster aggregation to larger structures is favourable, the anchoring of the nanocluster on the TiO2 surface actually disfavours nanocluster aggregation and indicates that these nanoclusters will be stable as isolated species.…”

“…In terms of understanding photocatalytic properties of surface modified TiO2, we next examine the projected electronic density of states (PEDOS) and the PEDOS for selected TiO2 nanocluster-modified rutile systems is shown in Figure 6; this is a representative sample of compositions and PEDOS plots for all the TiO2 nanocluster-modified rutile systems we have studied are presented in refs [79][80][81] .…”

“…In addition, 4-fold Ti species present in the free nanocluster can still persist in upon formation of the composite structure. A detailed discussion of the geometry in these composite structures is presented in refs [79][80][81] . (a) Reproduced from [80] , 2011, The Royal Society of Chemistry (b), (c) Reproduced from [79] , 2013, The Royal Society of Chemistry…”

“…In our work on surface modified TiO2, we have chosen TiO2 nanocluster-modified rutile (110) as our model system [79][80][81] to explore the many factors involved in devising photocatalysts that were outlined in the previous section. Figure 5 shows the atomic structure of free and supported TiO2 nanoclusters, ranging from a Ti2O4 "molecule" to a 1.5 nm diameter Ti30O60…”