The photocatalytic reduction of CO2 over titania-based materials is an attractive means for harnessing solar energy for the production of fuels such as CO. Recent work in our group focuses on the design of multifunctional nanostructured metal oxides able to undergo controlled redox cycling and electron transfer to reactants under the action of both light and heat. This work explores the idea of CO2 as a soft oxidant which heals oxygen vacancies in the supported oxide to produce CO, and H2O as a reducing agent to regenerate these oxygen vacancies (see figure).Here we present results on the effects of synthesis parameters (support material, metal oxide precursor, metal loading) on the optical and photocatalytic properties of manganese oxide (MnOx) clusters supported on titania. MnOx-TiO2 catalyst were prepared by incipient wetness impregnation of TiO2 nanopowder supports (anatase and rutile) with aqueous solutions of manganese (II) nitrate and manganese (II) acetate over a range of manganese loadings. Diffuse reflectance UV-visible light spectroscopy shows a red-shifted photoresponse in the MnOx-TiO2 materials when compared to the bare supports. The magnitude of adsorption edge shift increases with increasing Mn loading. X-ray diffraction indicates a lack of large crystalline MnOx domains, even at the highest Mn loadings, while thermogravimetric analysis under oxidizing and reducing conditions indicates the presence of redox active centers capable of reversible cycling at mild temperatures. Results of photocatalytic activity testing are also presented.

Titania supported manganese oxide nanocomposites for solar fuel production

248th National Meeting (2014)

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