Compound characterization data — Fornero et al., 2026

Pt(111)
Time-resolved MS, m/z = 44 (CO₂), PCO = 1 × 10⁻⁵ mbar, PO₂ = 1 × 10⁻⁵ or 5 × 10⁻⁵ mbar, 425–500 K, 5 s CO-on and 11 s CO-off intervals, average of 110 cycles	For both O₂ pressures, a primary CO₂ production peak appeared immediately after the valve opened, followed by a decrease in CO₂ production, and a secondary CO₂ production peak appeared after the valve closed. At 1 × 10⁻⁵ mbar O₂, the initial peak was of similar magnitude at all four temperatures; the steady-state CO₂ production rate increased with temperature; higher steady-state rates led to higher secondary peaks; and the second peak shifted to later times as temperature decreased. At 5 × 10⁻⁵ mbar O₂, all CO₂ production rates increased; the first-peak increase was more prominent at lower temperatures; and all secondary peaks shifted to earlier times while retaining the same temperature ordering
Time-resolved IRRAS, PCO = 1 × 10⁻⁵ mbar, PO₂ = 1 × 10⁻⁵ or 5 × 10⁻⁵ mbar, 425–500 K, 5 s CO-on and 11 s CO-off intervals, average of 110 cycles	The full 2020–2160 cm⁻¹ spectral region showed buildup of the linearly bound CO band during CO exposure and its disappearance after valve closure; depletion became faster as either temperature or O₂ pressure increased. The CO stretching region was typically integrated over 2030–2140 cm⁻¹
Work function, 473 K	The measured work function of clean Pt(111) was 6.32 ± 0.05 eV. Using 6.10 eV as the clean-Pt(111) reference, a common correction of −0.22 eV was applied to all reported values. The corrected work function was 5.47 ± 0.05 eV under approximately 1 × 10⁻⁷ Torr CO and 5.77 ± 0.05 eV under approximately 1 × 10⁻⁷ Torr O₂
Work function, CO:O₂ = 1:22.4, O₂ feed fraction = 0.957, PO₂ = 1.12 × 10⁻⁷ Torr, 473 K	5.68 eV
Work function, CO:O₂ = 1:7.0, O₂ feed fraction = 0.875, PO₂ = 1.12 × 10⁻⁷ Torr, 473 K	5.64 eV
Work function, CO:O₂ = 1:4.8, O₂ feed fraction = 0.828, PO₂ = 1.12 × 10⁻⁷ Torr, 473 K	5.58 eV
Work function, CO:O₂ = 1:37.3, O₂ feed fraction = 0.974, PO₂ = 1.12 × 10⁻⁷ Torr, 473 K	5.68 eV
Work function, CO:O₂ = 1:14.0, O₂ feed fraction = 0.933, PO₂ = 1.12 × 10⁻⁸ Torr, 473 K	5.62 eV
Work function, CO:O₂ = 1:1.2, O₂ feed fraction = 0.545, PO₂ = 1.12 × 10⁻⁸ Torr, 473 K	5.58 eV
Work function, CO:O₂ = 4.4:1, O₂ feed fraction = 0.185, PO₂ = 1.12 × 10⁻⁸ Torr, 473 K	5.54 eV
Work function, CO:O₂ = 10:1, O₂ feed fraction = 0.091, PO₂ = 1.12 × 10⁻⁸ Torr, 473 K	5.51 eV

Au(111)
Time-resolved MS, m/z = 44, CO/O₂ pulsing protocol	A small background response and no pronounced dual-peak structure were observed

CO adsorbed on Pd(111)
IRRAS, 450 K, pulsing-valve and continuous CO dosing	The spectrum obtained with the pulsing valve at an ion-gauge reading of 1 × 10⁻⁵ mbar closely matched the continuous-dose spectrum at 1 × 10⁻⁵ mbar in peak position, approximately 1874 cm⁻¹, and absorbance