Hydrogen adsorption and diffusion on Pt {111} and PtSn {111}

Abstract

PtSn {111} forms two ordered surface alloys namely p(2 6 2) and (!3 6 !3R30u) and such bimetallic catalysts are often used in industrially catalysed reactions, such as hydrogenations, to improve performance although the reasons behind the improvements are generally not well understood. In this study density functional theory calculations have been performed for hydrogen adsorption at various sites on Pt {111} and the ordered PtSn {111} surfaces in order to characterise the differences between the pure and doped surfaces. The structural, bonding, electronic and vibrational characteristics of each system are presented indicating that there are no significant bonding differences when adsorption occurs at platinum sites on the surface. Where adsorption occurs at a tin site on the doped surface the adsorption energy is negative or the adsorption site changes to one involving only platinum atoms. Nudged elastic band calculations were used to determine the barrier to diffusion of the hydrogen atoms on the surface. The diffusion calculations show significant differences in the mobility of hydrogen providing a possible explanation for the changes in catalytic action on tin doping of platinum.

SiC-based MIS gas sensor for high water vapor environments

“…5a. According with Langmuir's isotherm an exponent n equal to 2 indicates that the adsorption of hydrogen is dissociative (i), which is consistent with studies of the hydrogen adsorption on Pt surfaces in dry atmospheres reported in the literature [29][30][31][32][33][34].…”

Weakly-bound hydrogen on defected Pt(111)

“…The diffusion of atomic hydrogen into the subsurface of smooth, but not on defected, Pt(111) surfaces has been suggested experimentally [23,47] and theoretically [48,49].…”

Tuning the chemical activity through PtAu nanoalloying: a first principles study

“…Apparently, one can notice a systematic increase in the adsorption energy in the order of 0.08 eV as a function of increasing Pt/Au ratios having a lowest value of 0.43 eV corresponding to Au 201 H and a highest value of 1.11 eV corresponding to Pt 201 H. The adsorption energy obtained for Pt 201 H from this work is apparently higher (nearly three times) than that of the bridgePtPt site on a Pt111 surface reported in ref. 19. The experimental values of H adsorption on Pt111 scatters between 0.30 and 0.99 eV.…”