Interfacial structure of atomically flat polycrystalline Pt electrodes and modified Sauerbrey equation. Issue 33 (5th July 2017)

• Record Type: Journal Article
• Authors: Kim, Jutae; Urchaga, Patrick; Baranton, Stève; Coutanceau, Christophe; Jerkiewicz, Gregory
• Is Part Of: Physical chemistry chemical physics. Volume 19:Issue 33(2017)
• Page Start: 21955
• Page End: 21963
• Publication Date: 2017-07-05
• Subjects: Chemistry, Physical and theoretical -- Periodicals; 541.3
• DOI: 10.1039/c7cp02528a
• Languages: English
• ISSNs: 1463-9076

Abstract

Abstract : Interfacial mass changes increase linearly with surface roughness and their analysis yields the interfacial structure of atomically flat polycrystalline Pt electrodes. Abstract : The electrochemical quartz-crystal nanobalance (EQCN) measures in situ mass changes associated with interfacial electrode processes. Real electrodes are not atomically flat, thus their surface roughness affects the conversion of frequency variations (Δ f ) to mass changes (Δ m ) associated with electrochemical processes. Here, we analyze Δ m associated with the electrochemical H adsorption/desorption and surface oxide formation/reduction on Pt electrodes of gradually increasing surface roughness using the EQCN and cyclic-voltammetry in an aqueous H2 SO4 solution. These two interfacial processes are ideal to probe changes in the electrochemically active surface area. The surface roughness of Pt-coated resonators is fine-tuned through Pt electrodeposition and examined using atomic force microscopy. The results acquired using Pt electrodes of increasing roughness factor (1.61 ≤ R ≤ 13.0) reveal a linear relationship between Δ m and R . Extrapolation of this relationship to R = 1.00 leads to the determination of Δ m associated with H adsorption/desorption and oxide formation/reduction on an atomically flat polycrystalline Pt electrode. The values of Δ m associated with these processes are analyzed in terms of the number of H, O, water, and ionic species interacting with each Pt atom of the electrode surface. We find that the charge densities associated with these electrochemical processes and mass variations do not scale up by the same factor. This leads to a modified version of the Sauerbrey equation for Pt electrodes, which takes into account the intrinsic surface roughness.