To assess the possibility of controlling
the desorption temperature
of palladium-absorbed hydrogen (Habs) through surface structural
manipulation, we investigated coadsorption systems of H and CO on
Habs-charged Pd(110) surfaces through temperature-programmed
desorption, low-energy electron diffraction, and H-depth profiling
by nuclear reaction analysis (NRA). A CO coverage of 0.5 ML lifts
the H-induced (1 × 2) pairing-row (PR) reconstruction on Habs precharged Pd(110), and, as on clean Pd(110), heating Pd(110)
(1 × 1) holding 0.3–1.0 ML of CO gives rise to a missing-row
(MR) structure. Whereas Habs desorbs through surface defects
of clean, PR-reconstructed Pd(110) at 160 K, CO coadsorption onto
Habs-loaded Pd(110) gives rise to three new high-temperature
shifted Habs desorption modes at 200, 270, and 375 K that
are assigned to different exit sites for resurfacing Habs atoms at regular terraces of the individual Pd(110) structures,
i.e., the (1 × 2) PR, bulk-terminated (1 × 1), and (1 ×
2) MR reconstruction, respectively. Our results thus manifest the
ability to control the Habs desorption temperature through
surface restructuring in well-defined CO coverage regimes. Furthermore,
the long-speculated transfer of chemisorbed H into the Pd interior
upon CO coadsorption is confirmed directly by NRA, revealing also
that all Habs diffuses into the Pd bulk at 200 K.