HP Chamber

The current project underway in the High Pressure Cell Chamber focuses on the reactivity of s-IrO2(110), a late transition metal oxide, and its ability to selectively oxidize light alkanes. The IrO2(110) surface is extremely good at promoting the activation of the initial C-H bond in light alkanes, which then leads to alkane dissociation at low temperatures. Our group has recently discovered that the IrO2(110) surface promotes the activation and subsequent dissociation of methane at 90 K. From this finding, it was later found that IrO2(110) can selectively oxidize ethane to ethlyene with a conversion of ~40% at ~400 K. The continuation of this study aims to increase the selectivity of the film towards partial oxidation of light alkanes by replacing the reactive surface oxygen (Obr) with chlorine atoms. By reducing the amount of available oxygen, we hope to limit the complete oxidation of light alkanes to combustion products (COx) and instead increase the yield of value added products such as ethylene.

The IrO2(110) film is very challenging to create in ultra high vacuum conditions (UHV) due to the stability of the substrate on which it is made, Ir(100) surface. In order to combat this limitation, our film is grown in a custom built high pressure cell located directly beneath our chamber, which is accessed via a re-entrance tube. Two sliding seals separate the cell and the UHV chamber which allows the main chamber to maintain UHV pressures while exposing the sample to high pressures of oxygen.

In addition to a high pressure cell, this chamber is equipped with a mass spectrometer, a low energy electron diffraction optic, and an auger electron spectroscopy optic. This provides us with a method of determining of reaction kinetics of the film as well as with a method by which to characterize the surface. We are currently designing a fourier transform infared spectroscopy system to determine reaction pathways for alkane oxidation via adsorbate chemical bonding.

Another goal of this project is to determine the reaction kinetics of the oxidation of light alkanes through the use of x-ray photoelectron spectroscopy. Further, we aim to determine whether the combustion of methane and formation of ethylene from ethane can be achieve at steady state conditions at higher pressure. To perform these experiments we travel to external synchrotron facilities that allow us to collect high resolution data at near ambient pressure conditions. Some external facilities we have traveled to include the National Synchrotron Light Source in Brookhaven, New York and MAX IV in Lund, Sweden.