Adsorption States of N2/H2Activated on Ru Nanoparticles Uncovered by Modulation-Excitation Infrared Spectroscopy and Density Functional Theory Calculations

David S. Rivera Rocabado, Tomohiro G. Noguchi, Shio Hayashi, Nobutaka Maeda, Miho Yamauchi, Takayoshi Ishimoto

Research output: Contribution to journalArticlepeer-review

3 Citations (Scopus)

Abstract

The adsorption states of N2 and H2 on MgO-supported Ru nanoparticles under conditions close to those of ammonia synthesis (AS; 1 atm, 250 °C) were uncovered by modulation-excitation infrared spectroscopy and density functional theory calculations using a nanoscale Ru particle model. The two most intense N2 adsorption peaks corresponded to the vertical chemisorption of N2 on the nanoparticle's top and bridge sites, while the remaining peaks were assigned to horizontally adsorbed N2 in view of the site heterogeneity of Ru nanoparticles. Long-term observations showed that vertically adsorbed N2 molecules gradually migrated from the top sites to the bridge sites. Compared to those adsorbed vertically, N2 molecules adsorbed horizontally exhibited a lower dipole moment, an increased N-N bond distance, and a decreased N-N bond order (i.e., were activated), which was ascribed to enhanced Ru-to-N charge transfer. H2 molecules were preferentially adsorbed horizontally on top sites and then rapidly dissociated to afford strongly surface-bound H atoms and thus block the active sites of Ru nanoparticles. Our results clarify the controversial adsorption/desorption behavior of N2 and H2 on AS catalysts and facilitate their further development.

Original languageEnglish
Pages (from-to)20079-20086
Number of pages8
JournalACS nano
Volume15
Issue number12
DOIs
Publication statusPublished - Dec 28 2021

All Science Journal Classification (ASJC) codes

  • Materials Science(all)
  • Engineering(all)
  • Physics and Astronomy(all)

Fingerprint

Dive into the research topics of 'Adsorption States of N2/H2Activated on Ru Nanoparticles Uncovered by Modulation-Excitation Infrared Spectroscopy and Density Functional Theory Calculations'. Together they form a unique fingerprint.

Cite this