In situ formation of catalytically active graphene in ethylene photo-epoxidation.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 30076295.
- Also identified by DOI 10.1038/s41467-018-05352-9 and PMC identifier 6076287.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
Ethylene epoxidation is used to produce 2 × 10<sup>7</sup> ton per year of ethylene oxide, a major feedstock for commodity chemicals and plastics. While high pressures and temperatures are required for the reaction, plasmonic photoexcitation of the Ag catalyst enables epoxidation at near-ambient conditions. Here, we use surface-enhanced Raman scattering to monitor the plasmon excitation-assisted reaction on individual sites of a Ag nanoparticle catalyst. We uncover an unconventional mechanism, wherein the primary step is the photosynthesis of graphene on the Ag surface. Epoxidation of ethylene is then promoted by this photogenerated graphene. Density functional theory simulations point to edge defects on the graphene as the sites for epoxidation. Guided by this insight, we synthesize a composite graphene/Ag/α-Al<sub>2</sub>O<sub>3</sub> catalyst, which accomplishes ethylene photo-epoxidation under ambient conditions at which the conventional Ag/α-Al<sub>2</sub>O<sub>3</sub> catalyst shows negligible activity. Our finding of in situ photogeneration of catalytically active graphene may apply to other photocatalytic hydrocarbon transformations.