Surface Diffusion of Underpotential‐Deposited Lead Adatoms on Gold Nanoelectrodes. Issue 12 (16th June 2021)

• Record Type: Journal Article
• Authors: Zhang, Baodan; Wang, Wei; Liu, Cheng; Han, Lianhuan; Peng, Juan; Oleinick, Alexander; Svir, Irina; Amatore, Christian; Tian, Zhong‐Qun; Zhan, Dongping
• Is Part Of: ChemElectroChem. Volume 8:Issue 12(2021)
• Page Start: 2282
• Page End: 2287
• Publication Date: 2021-06-16
• Subjects: underpotential deposition -- Faradaic adsorption -- surface diffusion -- nanoelectrode -- cyclic voltammetry; Electrochemistry -- Periodicals; 541.37
• DOI: 10.1002/celc.202100516
• Languages: English
• ISSNs: 2196-0216

Abstract

Abstract: A simple and readily applicable voltammetric approach is described to characterize and measure the site‐hopping surface diffusion of underpotential‐deposited (UPD) metal adatoms at nanoelectrodes. UPD refers to the deposition of atoms on foreign metal supports at potentials lower than those predicted by Nernst law for a bulk deposition. Despite its importance in several fields of catalysis, advanced nanofabrication or even atomic nanoengineering by atomic layer epitaxy, diffusion of UPD adatoms is difficult to observe at micro‐ and macroelectrodes. In fact, at electrodes of usual dimensions, UPD adatoms surface diffusion is masked by other electrochemical phenomena of greater relative amplitudes. Conversely, at nanowires electrodes sealed in glass, only an extremely small fraction of the surface of the wires is exposed to the electrolyte solution and is rapidly loaded. This allows the spillage of UPD adatoms onto the much larger area of the nanowire rod which is immune to Faradaic reactions due to its isolation from the electrochemical solution by the glass casing. Therefore, surprisingly for a UPD process, voltammetric peaks currents and integral desorption charges primarily reflect these diffusional surface processes so that the integral charges vary linearly with the inverse of the square root of the scan rate. This is easily observable and measurable with usual bench‐level electrochemical instrumentation. In this work, by using nanoelectrodes with diameters between 90 and 260 nm, we were able to establish the major involvement of this site‐hopping surface diffusion of UPD Pb adatoms on polycrystalline gold (Au) and characterize it quantitatively. The equivalent surface diffusion coefficient of UPD Pb adatoms was determined to be ∼4.4×10 −11 cm 2 s −1 at room temperature, corresponding to a Gibbs free energy activation barrier of ca. 18.72 kJ mol −1 (i. e., 0.19 eV per Pb adatom) for the reaction of inter‐sites exchange of Pb adatoms on a polycrystalline Au surface. Abstract : The diffusion kinetics of underpotential‐deposited lead adatoms on polycrystalline gold surfaces were investigated at nanoelectrodes using simple voltammetry, providing facile measurements of the corresponding site‐hopping equivalent surface diffusion coefficient, ∼4.4×10 −11 cm 2 s −1 at 25 °C, and of its associated 18.72 kJ mol −1 Gibbs free energy barrier. This attractive and simple methodology is significant for metal electrode processes, electrocatalytic interface engineering, nano‐ and atomic fabrications.