Formation and thermal stability of subsurface deuterium in Ni(110)

• Published in: Surface science 2018-08, Vol.674, p.69-72
• Main Authors: Yang, Yuxin, Hofman, Michelle S., Koel, Bruce E.
• Format: Article
• Language: English
• Subjects: Adatoms; Catalysis; Catalysts; Desorption; Deuterium; Deuterium atom; Deuterium ion; Electrons; Hydrogen; Hydrogen storage; Ions; Substrates; Subsurface deuterium; Surface stability; Temperature effects; Temperature programmed desorption; Thermal stability
• ISSN: 0039-6028; 1879-2758
• DOI: 10.1016/j.susc.2018.04.001

•The uptake and thermal desorption of deuterium on a Ni(110) surface has been measured using incident gaseous D2 molecules, D atoms, and D2+ ions.•Molecular D2 exposures on a Ni(110) surface at 90 K under UHV conditions does not populate subsurface deuterium binding states, but incident D atoms and D2+ ions do.•The temperature of the D2 thermal desorption peak arising from subsurface deuterium is dependent on the energy of the incident deuterium species.•The thermal stability and D2 TPD peaks from subsurface D atoms are nearly the same at Ni(110) and Ni(111) surfaces. A unique feature of plasma-enhanced catalysis compared to thermal catalysis is the presence of reactive hydrogen radicals and ions in the gas phase above the catalyst surface. The uptake and subsequent thermal desorption of deuterium on a Ni(110) surface have been measured using incident gaseous D2 molecules, D atoms, and D2+ ions. Molecular D2 exposures on Ni(110) at 90 K form adsorbed D adatoms at the surface, but do not populate subsurface deuterium binding states under UHV conditions. In contrast, such subsurface states on Ni(110) are readily populated at 90 K by incident D atoms and D2+ ions. Subsurface D atoms recombine to desorb as D2 gas in temperature programmed desorption (TPD) measurements to create new characteristic subsurface-derived D2 thermal desorption peaks near 175 K for incident D atoms and 190–260 K, depending on the energy of the incident D2+ ions used, along with a new peak at 435 K for incident ions. While there are small differences for adsorbed D adatoms on Ni(110) and Ni(111) surfaces regarding their thermal stability and subsequent D2 TPD curves, the thermal stability and D2 TPD peaks from subsurface D atoms are nearly the same for these two substrates. This information will be helpful for a fuller understanding of the role of subsurface hydrogen and its reactivity in hydrogenation for plasma-enhanced catalysis over Ni-based catalysts. [Display omitted]