Interactions of incident H atoms with metal surfaces

Michelle S. Hofman, Dwayne Z. Wang, Yuxin Yang, Bruce E. Koel

Research output: Contribution to journalReview articlepeer-review

5 Scopus citations

Abstract

Atomic hydrogen is a highly reactive species of interest because of its role in a wide range of applications and technologies. Knowledge about the interactions of incident H atoms on metal surfaces is important for our understanding of many processes such as those occurring in plasma-enhanced catalysis and nuclear fusion in tokamak reactors. Herein we review some of the numerous experimental surface science studies that have focused on the interactions of H atoms that are incident on low-Miller index metal single-crystal surfaces. We briefly summarize the different incident H atom reaction mechanisms and several of the available methods to create H atoms in UHV environments before addressing the key thermodynamic and kinetic data available on metal and modified metal surfaces. Generally, H atoms are very reactive and exhibit high sticking coefficients even on metals where H2 molecules do not dissociate under UHV conditions. This reactivity is often reduced by adsorbates on the surface, which also create new reaction pathways. Abstraction of surface-bound D(H) adatoms by incident H(D) atoms often occurs by an Eley-Rideal mechanism, while a hot atom mechanism produces structural effects in the abstraction rates and forms homonuclear products. Additionally, incident H atoms can often induce surface reconstructions and populate subsurface and bulk absorption sites. The absorbed H atoms recombine to desorb H2 at lower temperature and can also exhibit higher subsequent reactivity with adsorbates than surface-bound H adatoms. Incident H atoms, either directly or via sorbed hydrogen species, hydrogenate adsorbed hydrocarbons, sulfur, alkali metals, oxygen, halogens, and other adatoms and small molecules. Thus, H atoms from the gas phase incident on surfaces and adsorbed layers create new reaction channels and products beyond those found from interactions of H2 molecules. Detailed aspects of the dynamics and energy transfer associated with these interactions and the important applications of hydrogen in plasma processing of semiconductors are beyond the scope of this review.

Original languageEnglish (US)
Pages (from-to)153-189
Number of pages37
JournalSurface Science Reports
Volume73
Issue number4
DOIs
StatePublished - Aug 2018

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Chemistry(all)
  • Condensed Matter Physics
  • Surfaces and Interfaces
  • Surfaces, Coatings and Films
  • Metals and Alloys
  • Materials Chemistry

Keywords

  • Absorption
  • Adsorption
  • Eley-Rideal mechanism
  • Hot atom mechanism
  • Hydrogen
  • Metal surfaces

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