Self-acceleration in the decomposition of acetic acid on Rh{111}: a combined TPD and laser induced desorption study

• Published in: Surface science Vol. 340; no. 1; pp. 23 - 35
• Main Authors: Hoogers, G., Papageorgopoulos, D.C., Ge, Q., King, D.A.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 10-10-1995
• Subjects: Carboxilic acid; Chemisorption; Laser induced thermal desorption (LITD); Low index single crystal surfaces; Rhodium; Surface chemical reaction; Thermal desorption spectroscopy; Chemisorption; Rhodium; Low index single crystal surfaces; Thermal desorption spectroscopy; Surface chemical reaction; Carboxilic acid; Laser induced thermal desorption (LITD)
• ISSN: 0039-6028; 1879-2758
• DOI: 10.1016/0039-6028(95)00673-7

Adsorption of acetic acid at 130 K on Rh{111} produces the following phases: multilayers (130–200 K); a mixed acetate/hydrogen monolayer (220–280 K); an acetate monolayer after desorption of hydrogen (> 300 K); and decomposition of acetate into hydrogen and carbon dioxide (∼ 400 K). Room temperature saturation of the clean surface and 200 K saturation of the surface with preadsorbed oxygen and/or potassium leads to sharp H
2 and CO
2 temperature-programmed-desorption (TPD) peaks, which are characteristic of self-accelerating processes. Oxygen is found to stabilize the acetate, causing it to decompose at a higher temperature; potassium destabilizes the acetate, and
O
K
mixtures have an intermediate effect. The results in the absence of co-adsorbed species are discussed in terms of a simple two-step empty-site-creation autocatalytic mechanism for systems in which most of the surface is initially fully saturated with adsorbate species. This mechanism is verified by laser-induced thermal decomposition and desorption. In the presence of co-adsorbates (O and/or K), mixed acetate-coadsorbate dense phases formed on the surface cause the acetate to decompose in an autocatalytic manner, and both electronic interactions as well as site blocking influence the desorption temperature.