Broadband Sum Frequency Generation Studies of Surface Intermediates Involved in Fuel Cell Electrocatalysis - Fuel Cell Catalysis: A Surface Science Approach - page 382

Figure 12.10 Analysis of SFG spectra from atop CO on Pt(111) using a CO-saturated 0.1 M
H 2 SO 4 electrolyte and a scan rate of 5 mV/s. The (2 2)23CO ! (

p

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p

)R23.482
13CO phase transition resulted in a jump in atop amplitude (a). Stark tuning (b) and peak width
versus electrode potential data (c) are also shown. (Filled circles denote linear Stark tuning behavior
while open circles correspond to deviations from linear behavior during oxidation.)

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Overall [Lagutchev et al., 2006], we investigated the CO phase transition where the
relative proportions of atop, bridge and 3-fold sites change significantly across the
phase boundary [Villegas and Weaver, 1994; Severson et al., 1995]. We found that
the SFG intensity changes for these sites were different from what was expected
solely on the basis of surface coverage densities. The explanation is that these sites
have quite different back-bonding, so the adlayer transition changes not only the