Photocatalysis uses light to excite electrons in a semiconducting material and the photogenerated electrons and hole are used to reduce or oxidise molecules. For example, if TiO2 is excited by UV light, since its band gap lies in the UV region, the photogenerated electrons and holes can be used to reduce CO2 (along with hydrogen) to fuels or oxidised water to produce oxygen. This opens up a vista of using cheap materials and light to produce fuels from CO2 or water which will meet the challenges of CO2 emissions, climate change and the next generation of energy sources.
We recently finished a Science Foundation Ireland Starting Investigator Grant (SIRG) "Engineering Metal Oxide Interfaces for Renewable Energy Applications (EMOIN)", in which we investigated metal oxide heterostructures composed of a nanscale metal oxide cluster adsorbed on TiO2 surfaces (rutile and anatase). A number of heterostructures have been investigated, among which TiO2 clusters adsorbed at rutile (110), FeOx clusters also adsorbed at rutile (110) and CrOx clusters adsorbed at rutile (110) show reduced band gaps compared with pure TiO2, which will induce visible light absorption. The heterostructure also allows for charge separation upon light excitation, thus making these structures potential visible light active photocatalysts. A collaboration with Prof. H. Tada in Japan, who synthesises these systems, shows excellent agreement between the calculations and the experiments.
In a follow-on to this project, we have started an SFI US-Ireland project with University of Ulster and Northwestern University to study CO2 reduction on surface modified TiO2.
Reactivity of sub 1nm Supported Clusters: (TiO2)n Clusters Supported on Rutile TiO2(110), A. Iwaszuk and M. Nolan, Physical Chemistry Chemical Physics, 2011, vol. 13, p. 3233
Surface Modification of TiO2 with Metal Oxide Nanoclusters: a Route to Composite Photocatalytic Materials, M. Nolan, Chemical Communications, 2011, vol. 47, p. 8617
Electronic Coupling in Iron Oxide-Modified TiO2 Leads to a Reduced Band Gap and Charge Separation for Visible Light Active Photocatalysis, M. Nolan, Physical Chemistry Chemical Physics, 2011, vol. 13, p. 18149
Tin oxide-Surface Modified Anatase Titanium(IV) Dioxide with Enhanced UV-Light Photocatalytic Activity, M. Fujishima, Q. Jin, H. Yamamoto, H. Tada and M. Nolan, Physical Chemistry Chemical Physics, 2012, vol. 14, p. 705
Molecular Metal Oxide Cluster-Surface Modified Titanium(IV) Dioxide Photocatalysts,H. Tada, A. Iwaszuk and M. Nolan, Australian Journal of Chemistry, 2012, vol. 65, p. 624 (Invited review for special issue on Global Artifical Photosynthesis)
The Photocatalytic Activities of Tin(IV) Oxide-Surface M odified Titanium (IV) Dioxide Show a Strong Sensitivity of the TiO2 Crystal Form, Q. Jin, M. Fujishima, M. Nolan, A. Iwaszuk and H. Tada, Journal of Physical Chemistry C, 2012, vol. 116, p. 12621
First Principles Prediction of New Photocatalyst Materials with Visible Light Absorption and Improved Charge Separation: Surface Modification of Rutile TiO2 with Nanoclusters of MgO and Ga2O3, M. Nolan, ACS Applied Materials and Interfaces, 2012, vol. 4, p. 5863
TiO2 Nanocluster Modified-Rutile TiO2 Photocatalyst: a First Principles Investigation,A. Iwaszuk, P. A. Mulheran and M. Nolan, Journal of Materials Chemistry A, 2013, vol. 1, p. 2515
Origin of the Visible Light Response of Nickel(II)Oxide Cluster-Surface Modified Titanium(IV) Dioxide, A. Iwaszuk, M. Nolan, Q. Jin, M. Fujishima and H. Tada,Journal of Physical Chemistry C, 2013, vol. 117, p. 2709
SnO-nanocluster modified anatase TiO2 photocatalyst: exploiting the Sn(II) lone pair for a new photocatalyst material with visible light absorption and charge carrier separation, A. Iwaszuk and M. Nolan, J. Mater. Chem. A, 2013, DOI:10.1039/C3TA10647K
Loading Effect in Copper (II) Oxide Cluster-Surface Modified Titanium (IV) Oxide on the Visible-and UV-Light Activities, Q Jin, M Fujishima, M Nolan, H Tada, A Iwaszuk, The Journal of Physical Chemistry C, 2013, vol. 117,
Lead Oxide-Modified TiO2 Photocatalyst: Tuning Light Absorption and Charge Carrier Separation by Lead Oxidation State, A Iwaszuk, M Nolan, Catal. Sci. Technol, 2013
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