Enhanced Catalysis under 2D Silica: A CO Oxidation Study

Abstract

Interfacially confined microenvironments have recently gained attention in catalysis, as they can be used to modulate reaction chemistry. The emergence of a 2D nanospace at the interface between a 2D material and its support can promote varying kinetic and energetic schemes based on molecular level confinement effects imposed in this reduced volume. We report on the use of a 2D oxide cover, bilayer silica, on catalytically active Pd(111) undergoing the CO oxidation reaction. We “uncover” mechanistic insights about the structure–activity relationship with and without a 2D silica overlayer using in situ IR and X‐ray spectroscopy and mass spectrometry methods. We find that the CO oxidation reaction on Pd(111) benefits from confinement effects imposed on surface adsorbates under 2D silica. This interaction results in a lower and more dispersed coverage of CO adsorbates with restricted CO adsorption geometries, which promote oxygen adsorption and lay the foundation for the formation of a reactive surface oxide that produces higher CO2 formation rates than Pd alone.

In situ preparation of a ferric polymeric aluminum chloride–silica gel nanocatalyst by mechanical grinding and its solid-phase catalytic behavior in organic synthesis

“…In conclusion, this study provides a successful strategy for the preparation of a a new composite silica gel–alumina–ferrate Lewis acid catalyst 41,54 and its efficient catalytic synthesis of organic chemicals. This strategy has effectively achieved the in situ chemical bonding reconstruction of conventional inorganic polymeric water treatment agents with a unique compositional structure and electronic properties with silica gel under solvent-free mechanical grinding, and easily prepared a new solid acid catalyst with high activity and stability, the PLASC catalyst.…”

“…This simple and gentle in situ reactive self-assembly mechanism on silica gel interfaces developed by the present method effectively regulates the microenvironment of the interface of the catalyst material, thus making the catalyst highly active and stable in organic solid-phase milling reactions and an efficient tool for the preparation of catalysts by mildly regulated chemical reactions. 54 Thus, this scheme is a new strategy for developing mild, energy-efficient, environmentally friendly and sustainable high-efficiency silicate-based complex acid catalysts.…”

Following the Kinetics of Undercover Catalysis with APXPS and the Role of Hydrogen as an Intercalation Promoter

“…In particular, we expect pulsing experiments to provide a better understanding of the limitations in catalyst reactivity induced by mass transport limitations. Ultimately, we hope that pulsing experiments will become a compelling method for tracking the underlying reason for the increased undercover activity reported below several 2D materials. ,,,, …”

“…The reactivity of the catalytic support can be enhanced due to the confinement of the adsorbates, which results in the modification of the relevant electronic states. This phenomenon has been studied for multiple reactions in a variety of systems ,,, such as graphene-covered nanoparticles, , covered polycrystalline surfaces, for solution-phase reactions, and under a variety of 2D materials other than graphene. − Moreover, with such novel model systems, one can obtain a fundamental atomic-scale understanding of confined chemistry, similar to the approach developed by Ertl for noncovered catalytic surfaces …”

“…Such understanding is in fact also highly relevant for confined catalytic systems in general, as such systems can suffer from mass transport limitations. While multiple groups have demonstrated lower activation energy for 2D covered surfaces, ,,,,− ,, studies specifically addressing mass transport limitations hardly exist in the literature.…”