Fig. 1. A cyclic voltammogram of Pt(111) in 0.5 M H₂SO₄, sweep rate 50 mV s⁻¹, T=25 °C.

Fig. 2. Relationship between the coverages of hydrogen and CO in the adlayer of the two co-adsorbed species as measured from cyclic voltammetry. 0.5 M H₂SO₄, T=25 °C. Solid line is a least-squares fit of the data for θ_CO<0.33, dashed line is an extrapolation of the fit to zero hydrogen coverage.

Fig. 3. Current transients of the oxidation of saturated CO adlayers on Pt(111), step potential is (a) 0.955, (b) 0.93, (c) 0.905, (d) 0.88, (e) 0.855, (f) 0.83, (g) 0.805, (h) 0.78, (i) 0.755, and (j) 0.73 V. Enlarged transient (g) is shown to indicate the pre-peak, current plateau and the main peak.

Fig. 4. Logarithm of the current in the plateau region vs. the step potential.

Fig. 5. Logarithm of the time of the main peak vs. the step potential. Solid line is the mean-squares fit of the experimental data, dashed line is a linear extrapolation of the fit.

Fig. 6. Current transient for CO adlayer oxidation on Pt(111), the step potential was 0.805 V. Experimental data (diamonds), fit by mean-field approximation (Eq. (6)) (solid line), fit by the progressive nucleation and growth model (dashed line). Only few experimental data points are depicted for the sake of clarity.

Fig. 7. Normalized current transients for CO adlayer oxidation on a contaminated Pt(111) surface after long experimentation (solid line) and on clean Pt(111) (dashed line), step potential was 0.805 V in both cases. Inset shows the corresponding voltammetric profile of this particular contaminated Pt(111) surface in 0.5 M H₂SO₄.

Fig. 8. Dependence of the apparent rate constant, determined by fitting the experimental data with Eq. (6), on the potential. Only the highest relative experimental errors are indicated.

Fig. 9. Current transients of the oxidation of sub-saturated CO adlayers on Pt(111), the step potential is 0.805 V, initial CO coverages are: (a) 0.04 (solid line), 0.18 (dotted line), 0.27 ML (dashed line); and (b) 0.31 (thin solid line), 0.43 (dotted line), 0.49 (dashed line), 0.58 ML (thick solid line).