Enhancing Au/TiO2 Catalyst Thermostability and Coking Resistance with Alkyl Phosphonic-Acid Self-Assembled Monolayers.

Metal oxide-supported Au catalysts, particularly those with small Au nanoparticles, catalyze a variety of reactions including low-temperature CO oxidation and selective hydrogenation of alkynes. However, the facile nature of Au particle growth at even moderate temperatures poses significant challenges to maintaining catalyst activity under reaction conditions. Here, we present a method to reduce the rate of sintering and coke formation in TiO2-supported Au catalysts via the deposition of alkyl-phosphonic acid (PA) self-assembled monolayers. After surface modification with PAs, the resultant catalysts exhibited significantly improved resistance to Au sintering. PA deposition strongly suppressed CO oxidation rates, consistent with poisoning of active sites. In contrast, modification with PAs significantly improved the rate of C2H2 hydrogenation on Au/TiO2. The enhanced activity was accompanied by a dramatically improved resistance to accumulation of surface carbonaceous species.