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Structure Revealing H/D Exchange with Co-Adsorbed Hydrogen and Water on Gold
A fundamental understanding of the interactions between
coadsorbed
water and hydrogen on metallic surfaces is critical to many chemical
processes including catalysis and electrochemistry. Here, we report
on the strong and intricate interactions between coadsorbed H/D and
water on the close-packed (111) surface of gold. Deuterium isotopic
labeling shows H/D exchange in H–D<sub>2</sub>O and D–H<sub>2</sub>O systems, indicating water dissociation and suggesting a
nonrandom scrambling process by revealing the origin of hydrogen evolution
(from surface H atoms or from water molecules) during annealing. In
this reaction, the protonation of the H-bonding ice network (i.e.,
the formation of (H<sub>2</sub>O)<sub><i>n</i></sub>H<sup>+</sup>) is energetically favorable and is responsible for water
dissociation. Density functional theory (DFT) modeling suggests that
the thermodynamics and structure of the protonated clusters are predominant
factors for yielding the traceable H<sub>2</sub> desorption features
from the surface interaction with H atoms, providing insights into
reaction mechanisms