Adsorption and Decomposition of a Lignin β-O-4 Linkage Model, 2-Phenoxyethanol, on Pt(111): Combination of Experiments and First-Principles Calculations

To sustain the current attempts in valorizing lignin-based derivatives, this study focuses on the decomposition upon a temperature ramp of 2-phenoxyethanol, a model for the beta-O-4 linkage in lignin, on a Pt(111) surface. Under ultrahigh-vacuum conditions, benzene, hydrogen, and carbon monoxide are the main desorbing products. Although benzene is the only aromatic desorbed product at low initial molecular coverages, very small amounts of phenol can be detected at higher initial coverage. Combining X-ray photoelectron spectroscopy and temperature-programmed desorption experiments together with density functional theory calculations, a reaction mechanism is suggested, starting with the OH bond scission. Phenoxy, PhO, is proposed as a key surface intermediate that preferentially deoxygenates rather than desorbs as phenol, similarly to the case of anisole. This behavior, typical of ultrahigh-vacuum conditions, is attributed to the reducing properties of carbonaceous surface species that efficiently deoxygenate phenoxy and afford the formation of the very stable carbon monoxide.