AVS 62nd International Symposium & Exhibition
    Surface Science Wednesday Sessions
       Session SS+AS+EN-WeA

Paper SS+AS+EN-WeA10
The Adsorption and Desorption of Small Hydrocarbons on Rutile TiO2(110)

Wednesday, October 21, 2015, 5:20 pm, Room 113

Session: Metals, Alloys & Oxides: Reactivity and Catalysis
Presenter: Long Chen, Pacific Northwest National Laboratory
Authors: L. Chen, Pacific Northwest National Laboratory
R.S. Smith, Pacific Northwest National Laboratory
B.D. Kay, Pacific Northwest National Laboratory
Z. Dohnalek, Pacific Northwest National Laboratory
Correspondent: Click to Email
The interaction of small hydrocarbons with metal and metal oxide surfaces is important for a wide range of applications including heterogeneous catalysis, atmospheric chemistry, geochemistry and chemical sensing. In this work, temperature programmed desorption (TPD) and molecular beam techniques are used to study the adsorption and desorption kinetics of small hydrocarbons (C1 - C4) on rutile TiO2(110) surface. In addition to n-alkanes, 1-alkenes (ethylene, propylene and 1-butylene) and 1-alkynes (acetylene, propyne and 1-butyne) were included to follow the effect of the nature of the carbon-carbon bond on hydrocarbon binding. We show that the sticking coefficients for all the hydrocarbons studied here are close to unity (> 0.95) at an adsorption temperature of 60 K. Similar to previous studies on metal and metal oxide surfaces, for n-alkanes on TiO2(110) we find a linear increase in desorption energy with chain length. In contrast, for 1-alkenes and 1-alkynes, a roughly linear relationship between desorption energy and chain length is also observed at low coverages, but with a much smaller slope, suggesting that the additional CHx segments either interact less efficiently with the substrate or destabilize the bonding of the unsaturated carbon-carbon bond. Further, we also determined the absolute saturation coverages of each hydrocarbon on the five-fold coordinated titanium sites (Ti5c). We show that except for CH4, the saturation coverages of the same type of hydrocarbons on Ti5c sites are nearly independent of the chain length, and that the saturation coverages of 1-alkynes consistently exceed those of n-alkanes and 1-alkenes, contrary to what one would expect based on their sizes.