Paper IS-FrM8
In Situ DRIFTS of TiO₂ Nanoparticles

Friday, November 11, 2016, 10:40 am, Room 101C

This project describes recent work focused on the surface chemistry of TiO₂ nanoparticles. These materials are commonly used in photocatalytic systems, where light induced reactions take place at the interface between the nanoparticle and an adsorbed sensitizing molecule. There are two primary classes of photocatalytic reactions: an adsorbate is excited by the light and interacts with the substrate, or the substrate is excited by the light and transfers an electron to the molecule. In both types of catalysis, it is the interaction of the adsorbate with the nanoparticle that truly drives the entire system. To optimize these catalytic processes, a better understanding of the interactions between the nanoparticles and the adsorbate is needed. In situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) is well suited for analyzing the surface reactions on TiO₂ nanoparticles. These powders are mostly transparent to the infrared and the multi-bounce nature of the diffuse reflectance helps to increase the signal from these low coverage reactions. This project explores, on a molecular level, the reactions between acetic acid and TiO₂ nanoparticles using in situ DRIFTS as a function of both temperature and relative humidity. To better understand the reactivity, different crystal structures of TiO₂, including anatase, rutile, and the commercially available P25 are investigated. Using DRIFTS and a high-temperature reaction chamber, we monitor surface changes when the TiO₂ is exposed to water and acetic acid. It is important to first understand how water alone reacts with the surface, creating a surface hydroxyl layer. After the reactivity between water and TiO₂ nanoparticles is clarified, the reaction of acetic acid with the surface of TiO₂ nanoparticles is investigated under a variety of different water coverages to better understand the role surface hydroxyls play in the reaction between acetic acid and TiO₂ nanoparticles.