Adsorption and Decomposition of 2(5H)-Furanone on Pd(111) and Pt(111): Comparison of Ring-Opening Pathways of an Unsaturated Cyclic Ester

Abstract

The thermal surface chemistry of 2(5H)-furanone (25HF) on Pd(111) and Pt(111) was studied using high-resolution electron energy loss spectroscopy (HREELS) and temperature-programmed desorption (TPD). After adsorbing 25HF on each surface at <140 K, increasing the temperature above 300 K resulted in opening and decomposition of the furanone ring. On both surfaces, 25HF undergoes decarbonylation and dehydrogenation to form CO and H 2 as the principal desorption products. A key difference between Pd(111) and Pt(111) reactivity is the relatively high amount of CO 2 produced from Pt(111), suggesting that 25HF decomposition proceeds in part through an additional surface intermediate on Pt(111). HREELS provides further indications that the reactions proceed through distinct pathways. On Pd(111), direct decarbonylation to surface CO and ethylidyne is observed. On Pt(111), two reaction pathways are proposed. One pathway is similar to the reaction pathway for Pd(111) and produces CO during TPD, and the other proceeds through an intermediate that retains the OCO functional group and results in CO 2 as a desorption product.