Polar Surface Domains and their Role in Photochemical Reactions

Gregory Rohrer^a, Paul Salvador^a, Ratiporn Munprom^a, Li Li^a, Andrew Schultz^a, Yiling Zhang^a

^aCarnegie Mellon University, Department of Materials Science and Engineering, Pittsburgh, 0, United States

Proceedings of International Conference on New Advances in Materials Research for Solar Fuels Production (SolarFuel14)

Montréal, Canada, 2014 June 25th - 26th

Organizer: Thomas Hamann

Invited Speaker, Gregory Rohrer, presentation 012
Publication date: 16th April 2014

Light driven water splitting is a promising renewable method to synthesize hydrogen. However, known catalysts are impractical either because of their high cost or low solar efficiency. Polar semiconductors have recently received significant attention because their internal fields separate photogenerated electron-hole pairs and reduce recombination. Domains of opposite polarization create unbalanced charge in spatially localized areas where the domains intersect the surface. As a result, electrons are attracted to positively terminated domains where they promote reduction reactions and holes are attracted to negatively charged domains where they promote oxidation. The separation of photogenerated carriers and redox products increases reactivity by limiting recombination and back reactions and this principle has been used to develop improved water splitting catalysts. In this talk, we will describe photochemical reactions on the surfaces of materials with polar domains. It will be demonstrated that polar domains can occur not only on the surface of ferroelectric materials, such as BaTiO3 or BiFeO3, but also on symmetrically non-polar materials such as SrTiO3 or BiVO4. In these later cases, polar surface terminations or strain gradients in the microstructure can lead to polar surface domains where they are not expected on the basis of only the known bulk properties. We will also present evidence that enhanced composite reactivity can occur when a heterostructure is formed by growing a thin titania layer over the polar surface domain.

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