Research output: Contribution to Journal/Magazine › Journal article › peer-review
Research output: Contribution to Journal/Magazine › Journal article › peer-review
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TY - JOUR
T1 - Electrochemistry at Ru(0001) in a flowing CO-saturated electrolyte-reactive and inert adlayer phases
AU - Alves, O. B.
AU - Hoster, H. E.
AU - Behm, R. J.
PY - 2011
Y1 - 2011
N2 - We investigated the electrochemical oxidation and reduction processes on ultrahigh vacuum prepared, smooth and structurally well-characterized Ru(0001) electrodes in a CO-saturated and, for comparison, in a CO-free flowing perchloric acid electrolyte by electrochemical methods and by comparison with previous structural data. Structure and reactivity of the adsorbed layers are largely governed by a critical potential of E = 0.57 V, which determines the onset of O(ad) formation on the CO(ad) saturated surface in the positive-going scan and of O(ad) reduction in the negative-going scan. O(ad) formation proceeds via nucleation and 2D growth of high-coverage Oad islands in a surrounding CO(ad) phase, and it is connected with CO(ad) oxidation at the interface between the two phases. In the negative-going scan, mixed (CO(ad) + O(ad)) phases, most likely a (2 x 2)-(CO + 2O) and a (2 x 2)-(2CO + O), are proposed to form at E <0.57 V by reduction of the O(ad)-rich islands and CO adsorption into the resulting lower-density O(ad) structures. CO bulk oxidation rates in the potential range E > 0.57 V are low, but significantly higher than those observed during oxidation of pre-adsorbed CO in the CO-free electrolyte. We relate this to high local CO(ad) coverages due to CO adsorption in the CO-saturated electrolyte, which lowers the CO adsorption energy and thus the barrier for CO(ad) oxidation during CO bulk oxidation.
AB - We investigated the electrochemical oxidation and reduction processes on ultrahigh vacuum prepared, smooth and structurally well-characterized Ru(0001) electrodes in a CO-saturated and, for comparison, in a CO-free flowing perchloric acid electrolyte by electrochemical methods and by comparison with previous structural data. Structure and reactivity of the adsorbed layers are largely governed by a critical potential of E = 0.57 V, which determines the onset of O(ad) formation on the CO(ad) saturated surface in the positive-going scan and of O(ad) reduction in the negative-going scan. O(ad) formation proceeds via nucleation and 2D growth of high-coverage Oad islands in a surrounding CO(ad) phase, and it is connected with CO(ad) oxidation at the interface between the two phases. In the negative-going scan, mixed (CO(ad) + O(ad)) phases, most likely a (2 x 2)-(CO + 2O) and a (2 x 2)-(2CO + O), are proposed to form at E <0.57 V by reduction of the O(ad)-rich islands and CO adsorption into the resulting lower-density O(ad) structures. CO bulk oxidation rates in the potential range E > 0.57 V are low, but significantly higher than those observed during oxidation of pre-adsorbed CO in the CO-free electrolyte. We relate this to high local CO(ad) coverages due to CO adsorption in the CO-saturated electrolyte, which lowers the CO adsorption energy and thus the barrier for CO(ad) oxidation during CO bulk oxidation.
KW - CARBON-MONOXIDE
KW - ACID-SOLUTIONS
KW - ADSORBATE INTERACTIONS
KW - OXIDATION REACTION
KW - ONLINE DEMS
KW - LEED-IV
KW - PT-RU
KW - ELECTROOXIDATION
KW - SURFACE
KW - OXYGEN
U2 - 10.1039/c0cp01001d
DO - 10.1039/c0cp01001d
M3 - Journal article
VL - 13
SP - 6010
EP - 6021
JO - Physical Chemistry Chemical Physics
JF - Physical Chemistry Chemical Physics
SN - 1463-9076
IS - 13
ER -