We have used high-energy X-ray photoelectron spectroscopy and diffraction (XPS/XPD), low-energy electron diffraction (LEED), high-resolution electron energy loss spectroscopy (HREELS) and temperature-programmed desorption (TPD) to determine the molecular orientation, long-range order, vibrational freequencies, and desorption temperatures for formic acid and its decomposition products on TiO2(110). Molecular adsorption occurs at coverages approaching one monolayer, producing a weakly ordered (2x1) surface structure. High-energy XPD reveals that the formate binds rigidly in a bidentate fashion through the oxygens to Ti cation rows along the [001] direction with an O-C-O bond angle of 126 +- 4 degrees. During TPD some surface protons and formate anions recombine and desorb as formic acid above 250 k. However, most of the decomposition products follow reaction pathways leading to H2O, CO and H2CO desorption. Water is formed in TPD below 500 K via the abstraction of lattice oxygen by deposited acid protons.
Revised: May 7, 2019 |
Published: February 1, 1998
Citation
Chambers S.A., M.A. Henderson, Y.J. Kim, and S. Thevuthasan. 1998.Chemisorption Geometry, Vibrational Spectra, and Thermal Desorption of Formic Acid on TiO2 (110).Surface Review and Letters 5, no. 1:381-385.PNNL-SA-27794.doi:10.1142/S0218625X98000700