| AVS 63rd International Symposium & Exhibition | |
| Surface Science | Wednesday Sessions |
| Session SS+AS-WeM |
| Session: | Environmental Interfaces, Ambient Surfaces, and In-Operando Studies |
| Presenter: | William DeBenedetti, Cornell University |
| Authors: | W.J.I. DeBenedetti, Cornell University M.A. Hines, Cornell University E.S. Skibinski, Cornell University A. Song, Cornell University A. Ortoll-Bloch, Cornell University |
| Correspondent: | Click to Email |
The surface chemistry of TiO2 in air and solution is an important, but under-studied, topic for next-generation photovoltaics, environmental remediation, and CO2 photoreduction. Using scanning tunneling microscopy (STM), polarized infrared spectroscopy and other techniques, we will show that surprisingly stable, near-ideal organic monolayers spontaneously form on rutile (110) in a variety of environments.
First, we will show that under ambient conditions, the rutile (110) surface is terminated by a monolayer of bicarbonate, HCO3, and H formed from the reactive adsorption of CO2 and H2O — a reaction that has never been observed in ultrahigh vacuum. Contrary to conventional wisdom, this bicarbonate monolayer displaces H2O bound to the surface, remaining intact even in vacuum up to ~700 K. The spontaneous formation of a HCO3 monolayer has important implications for the mechanism of CO2 photoreduction on TiO2.
Second, we will show that near-ideal organic monolayers form when rutile (110) is immersed in a variety of aqueous solutions. As an example, highly ordered benzoate monolayers with a characteristic “paired” geometry can be formed from aqueous solutions. Using polarized infrared spectroscopy, we show that this pairing is not due to dimerization, as suggested by previous researchers. Instead, DFT simulations confirm that π-π interactions lead to long-range ordering and a tetrameric bonding geometry. The structure of these monolayers is further confirmed by disrupting the π-π interactions using a variety of fluoro-substituted precursors.