Design and synthesis of model and practical palladium catalysts using atomic layer deposition

Abstract

We investigated the “one-batch” synthesis of model and practical palladium catalysts using atomic layer deposition (ALD). Two types of model catalysts and one type of powder-based nanocatalyst were synthesized simultaneously by ALD under viscous flow conditions. In addition, Pd/TiO₂(110) model catalysts were prepared by the identical ALD process but under ultrahigh vacuum conditions. Because of the self-limiting surface reaction that defines ALD, the local structure of all the Pd catalysts were essentially the same as confirmed by a suite of microscopic and spectroscopic characterization techniques. A comprehensive understanding of the Pd-based catalysts was achieved by applying both surface science probes and advanced synchrotron techniques, and by strategically selecting the catalyst substrate best suited for each characterization. Both X-ray absorption spectroscopy and X-ray resonant photoelectron spectroscopy suggested that Pd only weakly interacted with the TiO₂ support. The one-batch synthesis approach facilitated by ALD can potentially bridge the “synthesis gap” between model catalysts and practical catalysts.