Kraushofer, F., Haager, L., Eder, M., Rafsanjani-Abbasi, A., Jakub, Z., Franceschi, G., Riva, M., Meier, M., Schmid, M., Diebold, U., & Parkinson, G. S. (2022). Single Rh adatoms stabilized on α-Fe₂O₃(11̅02) by coadsorbed water. ACS Energy Letters, 7(1), 375–380. https://doi.org/10.1021/acsenergylett.1c02405
Renewable Energy, Sustainability and the Environment; Energy Engineering and Power Technology; Fuel Technology; Materials Chemistry; Chemistry (miscellaneous)
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Abstract:
Oxide-supported single-atom catalysts are commonly
modeled as a metal atom substituting surface cation sites in a low-
index surface. Adatoms with dangling bonds will inevitably coordinate
molecules from the gas phase, and adsorbates such as water can affect
both stability and catalytic activity. Herein, we use scanning tunneling
microscopy (STM), noncontact atomic force microscopy (ncAFM), and
X-ray photoelectron spectroscopy (XPS) to show that high densities of
single Rh adatoms are stabilized on α-Fe 2 O 3 (11̅02) in the presence of
2 × 10−8 mbar of water at room temperature, in marked contrast to the
rapid sintering observed under UHV conditions. Annealing to 50 °C in
UHV desorbs all water from the substrate leaving only the OH groups
coordinated to Rh, and high-resolution ncAFM images provide a direct
view into the internal structure. We provide direct evidence of the
importance of OH ligands in the stability of single atoms and argue that
their presence should be assumed when modeling single-atom catalysis systems.
