Compressive Stress and Charge Redistribution during CO Adsorption onto Pt

The change in surface stress associated with the adsorption and oxidative stripping of carbon monoxide (CO) on (111)-textured Pt is examined using the wafer curvature method in 0.1 mol/L KHCO₃ electrolyte. The curvature of the Pt cantilever electrode was monitored as a function of potential in both CO-free and CO-saturated electrolytes. Although CO adsorbs as a neutral molecule, significant compressive stress, up to -1.3 N/m, is induced in the Pt. The magnitude of the stress change correlates directly with the CO coverage and, within the detection limits of the stress measurement, is elastically reversible. Density functional theory calculations of a CO-bound Pt surface indicate that charge redistribution from the first atomic layer of Pt to subsurface layers accounts for the observed compressive stress induced by the charge neutral adsorption of CO. A better understanding of adsorbate-induced surface stress is critical for the development of material platforms for sensing and catalysis.