In Situ Scanning Tunneling Microscopy of Underpotential Deposition of Copper at Pt(100) Electrodes Coated with an Iodine Monolayer

Abstract

Reported here are in situ scanning tunneling microscopy (STM) results of underpotential deposition (UPD) of copper at an iodine-modified Pt(100) electrode. The cyclic voltammograms reveal that an iodine adlayer strongly adsorbed on Pt(100) resulted in a 350 mV delay of Cu deposition with respect to that of a bare Pt(100) electrode. High-quality in situ STM imaging reveals the atomic structures of the iodine adlayers before and after the deposition of Cu adatoms. Depending on the dosage of iodine vapor to an annealed Pt(100) electrode, two ordered structures of the iodine adatoms are formed and are characterized as ( 2 × 5 2)R45°and ( 2 × 9 2)R45°with coverage of 0.6 and 0.55, respectively. The predominant interadsorbate interaction results in adsorption of iodine at either symmetric 4-fold or asymmetric sites. Since the Cu deposit displaces the iodine adatoms on Pt(100), the iodine adatoms with weaker surface bonding are replaced first, leading to anisotropic deposition. Regardless of the initial iodine structures on Pt(100), deposition of Cu results in a c(2 × 2) structure. The deposition and dissolution processes are reversible with respect to the Cu adatoms but the iodine overlayer undergoes irreversible reconstruction from ( 2 × 5 2)R45°to c(2 × 2). In situ STM atomic imaging at the onset of bulk Cu deposition also reveals protruding islands with ordered c(2 × 2) structure of iodine adatoms, suggesting a pseudomorphic structure of the 2nd Cu adlayer.

In situ scanning tunneling microscopy study of cobalt thin film electrodeposited on Pt(111) electrode

“…The Pt(1 1 1) electrode was immersed from the quenching tube with a thin film of water on top, which protected this Pt electrode from adsorption of contaminants in the ambient. The STM cell was equipped with a Pt counter and a Pt quasi-reference electrodes [27][28][29]. All potentials reported here are converted into a scale of a Ag/AgCl electrode.…”

In Situ STM Imaging of Bis-3-sodiumsulfopropyl-disulfide Molecules Adsorbed on Copper Film Electrodeposited on Pt(111) Single Crystal Electrode

“…The Pt(111) electrodes used for STM and voltammetric experiments were made from a polycrystalline Pt wire. , The obtained Pt(111) bead electrode was fist annealed with a hydrogen torch, followed by quenching in hydrogen-saturated Millipore water. Pt wires were used as the counter and quasi-reference electrodes in the STM environment. − All potentials reported here are converted into the scale of a Ag/AgCl electrode. Prior to the deposition of a Cu film, the potential of Pt(111) was scanned negatively at 50 mV/s to −0.3 V (onset of hydrogen evolution) from the open-circuit potential (OCP) of ∼0.7 V. This potential sweeping removed the thermal oxide produced in the annealing-and-quenching pretreatment.…”

Role of Lithium Iodide Addition to Lithium Thiophosphate: Implications beyond Conductivity

“…The solution-based electrodeposition of metals has been extensively studied academically as well as provided industrial solutions for practical devices. , One interesting and applicable avenue of research has been the use of surface modifiers to affect the structure and morphology of deposited metals, for example, surfactants, organic molecules, and halide salts . In liquid-based electrochemical deposition, iodine adsorption on metal surfaces is well known to influence the kinetics of crystallization and the morphology of metal growth and has been frequently utilized to form compact, uniform films. − For solid-state electrodeposition, several research teams have shown that modification of the lithium-metal surface has significantly improved the galvanic cycling properties using solid-state electrolytes; − however, iodine adsorption has not been evident during the solid-state deposition of lithium metal nor has its influence on cell failure. Understanding the electrochemical interphase is a vital step to engineering practical SSBs.…”