(532dx) Dynamic Evolution of Metal Nanoparticles in Bifunctional Systems for Catalytic Chemical Upgrading

In recent years, a growing interest in the maximization of material efficiency within catalytic systems has become the driving force towards investigating and developing atomically dispersed single atom catalysts, both for environmental and economic motives. Precious noble metals, in particular, are rare, expensive, and non-renewable, inorganic materials. Thus, intricate design of systems that pursue the utmost noble metal atom utilization is key. Remarkable progress has been made in the development of synthetic routes that allow for the direct preparation of atomically dispersed species. From the strong electrostatic adsorption (SEA) method for the synthesis of supported single-atom catalysts, to the preparation of single-atom alloys via galvanic replacement, a myriad of successful synthethic strategies have emerged. ^1,2 An interesting alternative towards the formation of single-site materials is the modification of conventionally prepared metal-metal oxide catalysts through controlled oxidative and reductive treatments.

In this work, we present the development of a catalytic system in which supported and encapsulated Pd nanoparticles (NPs) in reducible metal oxides (MO) can be redispersed into small clusters and atomically dispersed species under specific treatment conditions. The catalysts were prepared by previously reported synthesis methods³ and were then treated under controlled gaseous environments to induce redispersion of the NPs into atomically dispersed species. Hence, we combined controlled synthesis and detailed characterization to shed light on the dynamical picture of the Pd-MO₂ catalytic interfaces under specific parameters both for supported and encapsulated structures. Our findings indicate that the reductive step of the treatment plays a major role in the redispersion of NPs, where temperature, time, and reduction agent become highly relevant factors. The treated materials were then probed for reactions involved in the production of value-added chemicals.

1. Nano Today 34, 100917 (2020).
2. J. Am. Chem. Soc. 139, 14150–14165 (2017).
3. Catal. Sci. Technol. 12, 1476–1486 (2022).