Substrate Control of TiO2 Reactivity

Gregory S. Rohrer, Carnegie Mellon University, DMR 0804770

Photochemical reactions on ceramic surfaces and heterostructures are being studied with the goal of understanding the principles that might be used to create improved catalysts for solar hydrogen production.

It has been discovered that the spatially selective reactivity on BaTiO3//TiO2 heterostructures is exactly the same as on the bare BaTiO3 substrate. Electrons and holes photogenerated in the BaTiO3 substrate pass through the TiO2 film to react at the surface.

These observations, which show that the initial hypothesis was incorrect, will allow the development of improved mechanistic models for composite photochemical properties. 5 m

(a) AFM image of a BaTiO3//TiO2 heterostructure; white contrast is PbO2 that has been photochemically oxidized in a spatially selective pattern.(b) AFM image of the same location after the film has been removed by polishing (contrast is from differential polishing)(c) AFM image showing pattern of PbO2 oxidized on the BaTiO3 substrate, which is the same as on the TiO2 film.

Undergraduate Team Studies Self-Cleaning Surfaces

Gregory S. Rohrer, Carnegie Mellon University, DMR 0804770

Undergraduate students worked together this summer to study the photochemical properties of self-cleaning surfaces.

Jonathan Senn (CMU) and Chrissi-Lee Williams (FAMU) developed a technique to deposit sub-monolayer films of steric acid on surfaces and to then monitor photochemical degradation by atomic force microscopy (AFM). This enables the systematic study of photochemically induced degradation of organics on oxide surfaces.

Beyond the technical goals of the project, the objective was to provide research experiences for undergraduates and to broaden participation of underrepresented groups.

(above) Undergraduate students working at the AFM. (below) AFM image of steric acid islands deposited by evaporation on a BaTiO3 surface.