Compressive Stress and Charge Redistribution during CO Adsorption Onto Pt

Abstract

Electroorganic reactions, where energy is either stored or released from chemical bonds within carbon-based molecules, are essential to help achieve a circular carbon-based economy. Central to electrochemical conversion of organic molecules is carbon monoxide (CO), which serves as both an intermediate in electrochemical CO2 reduction to hydrocarbons and electrochemical oxidation in fuel cells that operate via oxygenated hydrocarbons (e.g., ethanol, methanol). For the latter, Pt has been the predominate catalyst of choice, and substantial effort has been spent to identify the mechanistic details for complete oxidation of alcohol-based fuels. With CO conversion serving as an important if not rate-limiting step of the oxidative process, it is critical to understand the state of a catalytic surface when CO is present.The change in surface stress associated with the adsorption and oxidative stripping of CO on (111)-textured Pt is examined using the wafer curvature method in 0.1 mol/L KHCO3 electrolyte.1 The curvature of the Pt cantilever electrode was monitored as a function of potential in both CO free and CO-saturated electrolyte. 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 account 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 materials platforms for sensing and catalysis. References D. Raciti, K.A. Schwarz, J. Vinson, and G.R. Stafford, The Journal of Physical Chemistry C , 126, 4446-4457 (2022).