Behavior of Water on Chemically Modified Semiconductor Surfaces:  Toward Photochemical Hydrogen Production

Photochemical water splitting to hydrogen, a renewable and non-polluting fuel, and oxygen using energy from solar radiation is extremely important for a sustainable source of energy. Hydrogen and oxygen have been successfully produced by UV irradiation of aqueous suspensions of various semiconductor catalysts including TiO2 (and transition metal-loaded TiO2) and SrTiO3, but a detailed mechanism of the conversion of the active catalytic center remains unclear. Recently nitrogen and carbon doped materials, TiO2-xNx, and TiO2-xCx, have been synthesized and used as photocatalysts that utilize visible light (l>420 nm). If these preliminary results are borne out, the high photoconversion efficiency observed in the TiO2-xCx system is tantalizing, and it could potentially form the basis of a practical process for hydrogen generation. The catalytic activities and electronic properties of these materials may be strongly altered by thermal and chemical treatment. Unfortunately, there are only a few reports on the thermal properties of adsorbed water on well-defined surfaces of these materials. In this program we are studying both the adsorption of water on well-defined single crystals of the compounds mentioned above and the reaction of adsorbed water with and without irradiation, using photoemission, x-ray absorption spectroscopy, scanning tunneling microscopy, time resolved x-ray diffraction, and density functional theory calculations.

This program is supported by a Laboratory-Directed Research and Development Grant (LDRD). We acknowledge Brookhaven National Laboratory for this support.

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Last Modified: June 28, 2012