This work is aimed at developing a protocol based on surface limited redox replacement (SLRR) of underpotentially deposited (UPD) Pb layers for the growth of epitaxial and continuous Pt thin films on polycrystalline and single crystalline Au surfaces. Different from previously reported papers using SLRR in multiple immersion or flow cell setups, this work explores the one-cell configuration setup as an alternative to improve the efficiency and quality of the growth. Open circuit chronopotentiometry and quartz-crystal microbalance experiments demonstrate steady displacement kinetics and a yield that is higher than the stoichiometric Pt(II)−Pb exchange ratio (1:1). This high yield is attributed to oxidative adsorption of OHad taking place on Pt along with the displacement process. Also, ex situ scanning tunneling microscopy surface characterization reveals after the first replacement event the formation of a dense Pt cluster network that homogenously covers the Au surface. The Pt films grow homogenously wit...

From Au to Pt via Surface Limited Redox Replacement of Pb UPD in One‐Cell Configuration

This work is aimed at developing a protocol based on surface limited redox replacement (SLRR) of underpotentially deposited (UPD) Pb layers for the growth of epitaxial and continuous Pt thin films on polycrystalline and single crystalline Au surfaces. Different from previously reported papers using SLRR in multiple immersion or flow cell setups, this work explores the one-cell configuration setup as an alternative to improve the efficiency and quality of the growth. Open circuit chronopotentiometry and quartz-crystal microbalance experiments demonstrate steady displacement kinetics and a yield that is higher than the stoichiometric Pt(II)-Pb exchange ratio (1:1). This high yield is attributed to oxidative adsorption of OH(ad) taking place on Pt along with the displacement process. Also, ex situ scanning tunneling microscopy surface characterization reveals after the first replacement event the formation of a dense Pt cluster network that homogenously covers the Au surface. The Pt films grow homogenously with no significant changes in the cluster distribution and surface roughness observed up to 10 successive replacement events. X-ray diffraction analysis shows distinct (111) crystallographic orientation of thicker Pt films deposited on (111) textured Au thin films. Coarse energy dispersive spectroscopy measurements and finer X-ray photoelectron spectroscopy suggest at least 4 atom % Pb incorporating into the Pt layer compared to 13 atom % alloyed Cu when the growth is carried out by SLRR of Cu UPD.

http://ma.ecsdl.org/content/MA2011-01/26/1558.full.pdf

From Au to Pt via Surface Limited Redox Replacement of Pb UPD in One Pot Configuration

In its simplest manifestation, the electrochemical quartz crystal microbalance (EQCM) is a relatively new device for executing a classical technique, electrogravimetry. The advantages it brought were in situ applicability (notwithstanding prior misconceptions regarding damping by a contacting fluid), exceptional sensitivity and dynamic capability, thereby permitting real-time monitoring of changes in surface populations of species during electrochemically driven processes. The basis of the method relies on the storage and dissipation of energy injected into the interfacial region by a high frequency (megahertz) acoustic wave; the latter is generated by a piezoelectric (generally quartz) resonator. From modest early aspirations, largely associated with the deposition/dissolution of simple adsorbates and thin metal films, the technique has expanded in three strategic respects: materials, phenomena and methodology. In the first instance, extension to thick electroactive films (notably metal oxides and polymers) has generated considerable insight. Second, the sensitivity of the EQCM to viscoelastic phenomena, stress and interfacial slip has been recognized. Considerable attention has been given to viscoelastic processes in redox and conducting polymers: these have been parameterized in terms of shear moduli, whose variation with polymer structure and imposed conditions provides insight into polymer dynamics. Procedures exist for characterizing film stress in harder materials, but this is less well exploited. Interfacial slip remains a poorly understood area. Third, application in the context of diverse electrochemical control functions and integration with other in situ techniques provide many as yet unexploited opportunities. The extent to which these are realised will probably depend on the level of interpretation of the resultant data, which presently underuses the library of modelling protocols available.

The EQCM: electrogravimetry with a light touch

In situ measurements of water adsorption on a platinum electrode by an electrochemical quartz crystal microbalance

Composite polypyrrole films switchable between the anion- and cation-exchanger states

In situ underpotential deposition study of lead on silver using the electrochemical quartz crystal microbalance: Direct evidence for lead(II) adsorption before spontaneous charge transfer

Une microbalance electrochimique a cristal de quartz est utilisee pour etudier le depot de Pb(II) sur des electrodes d'or et d'argent dans des solutions de borate pour des pH de 8 a 10,5

Expulsion of borate ions from the silver/solution interfacial region during underpotential deposition discharge of lead(II) in borate buffers

Electrochemical quartz crystal microbalance (EQCM) studies of the underpotential deposition (UPD) of bismuth(III) at silver were performed in borate buffers in the pH range 8–10. A bismuth borate species is adsorbed at positive rational potentials. At more negative potentials the adsorbed species is reduced to UPD bismuth(o) and there is a concomitant decrease in electrode mass. The surface reduction process corresponds to the expulsion of four BO–2 anions from the interface according to the reaction Bi(BO–2)4+ 3e = Biupd+ 4BO–2. The EQCM technique has been demonstrated to be well suited to study the mechanism of underpotential deposition of metals and the stoichiometry of adsorbed surface complexes.

Expulsion of borate ions from the silver/solution interfacial region during underpotential deposition discharge of BiIII in borate buffer

In situ studies using the electrochemical quartz crystal microbalance (EQCM) have provided unique means for demonstrating the existence of adsorbed anionic lead species at silver and also for tracking anion expulsion during the underpotential deposition (UPD) discharge process. UPD studies of lead(II) at silver were carried out over the pH range 1 to 13. In perchloric acid solutions and acetate buffers, where only cationic and uncharged lead(II) species exist in solution, the UPD process is accompanied by an increase in the mass of the electrode. However, in borate buffers and sodium hydroxide solutions, where anionic lead(II) species predominate, the UPD process is accompanied by a decrease in electrode mass. This mass decrease is caused by the reduction of adsorbed, negatively charged lead(II) species to UPD Pb(0) and concomitant expulsion of the negatively charged ligand, borate or hydroxide. The potential of zero charge of silver is very negative so that the electrostatic adsorption of anionic lead(II) species is strongly favored, while cationic and uncharged lead(II) species, such as lead acetate, do not adsorb.

In situ Underpotential Deposition Study of Lead on Silver Using the Electrochemical Quartz Crystal Microbalance. Direct Evidence for Lead(II) Adsorption Before Spontaneous Charge Transfer.

Kenneth Kanige

Papers

In situ underpotential deposition study of lead on silver using the electrochemical quartz crystal microbalance: Direct evidence for lead(II) adsorption before spontaneous charge transfer

Expulsion of borate ions from the silver/solution interfacial region during underpotential deposition discharge of lead(II) in borate buffers

Expulsion of borate ions from the silver/solution interfacial region during underpotential deposition discharge of BiIII in borate buffer

In situ Underpotential Deposition Study of Lead on Silver Using the Electrochemical Quartz Crystal Microbalance. Direct Evidence for Lead(II) Adsorption Before Spontaneous Charge Transfer.