Effects of organic additives, such as benzoic acid (BA) and poly(ethylene glycol)s (PEGs), on the initial stage of the zinc electrodeposition have been investigated at iron electrodes using cyclic voltammetry, electrochemical quartz crystal microbalance measurements and in situ electrochemical scanning tunneling microscopy in an acidic zinc chloride solution in efforts to gain a molecular-level understanding of their roles. BA is adsorbed strongly at the sites of more negative potentials on the electrode, although it is randomly adsorbed on the iron surface at around an open circuit potential. Its role seems to control the deposition rate at the dendritic sites by blocking the active surface via adsorption. On the contrary, PEGs are adsorbed more or less evenly with a well-ordered structure on the iron surface and appear to desorb in the underpotential deposition region of zinc ions, which helps inhibit proton reduction by effectively blocking the electrode surface.

Organic conducting polymers have been studied extensively due to fundamental interests in reaction mechanisms as well as for their possible applications to practical devices including energy storage devices, electrochemical/chemical sensors, electrochromic devices, and others. 1-3 Most applications require repeated injection and removal of charges from bulk polymers via doping and dedoping processes. Some applications including sensors or electronic devices may eventually require nanosized polymer wires or dots. For this reason, nanosized conducting polymer wires have been prepared electrochemically using hollowed templates made from polycarbonates with neutron beams 4,5 or chemically using the zeolites. 6,7 The polymer wires were then obtained by dissolving polycarbonates or zeolites. Conducting polymer wires thus prepared generally had enhanced conductivity compared to that of bulk polymers. 5,7,8 Conducting polymers were generally grown on metal electrodes by potentiodynamic, potentiostatic, or galvanostatic methods. 3 Depending on the state of electrode surfaces, the overpotential for oxidation of monomer molecules is determined, which affects their film quality; an example includes oxidation of aniline for the preparation of polyaniline. Aniline requires a large overpotential at metal electrodes but once the polymer is formed on the electrode surface, the organic film usually reduces the overpotential for oxidation of monomer molecules, leading to what is called "autocatalytic mechanism." 3,9 When organic molecules lowering the aniline overpotential are adsorbed on the metal electrodes, the quality of polyaniline formed on the electrodes is generally improved to a great deal. 10 In rare cases, however, modified electrodes have been used to prepare conducting polymers.Recently, we reported use of cyclodextrin (CD) covered electrodes for performing molecular-size selective electrochemistry of a few quinone compounds. 11 The cavities created by thiolated CDs adsorbed on gold electrodes act as either an array of ultramicroelectrodes or anchoring sites depending on properties of molecules examined. It occurred to us that the CD-modified electrodes could be used as those offering anchoring sites for monomer molecules, which could lead to a possibility of growing polymers to our specification.We carried out our current study to (i) see how the polymerization site modification would affect the polymer growth, (ii) find whether or not the cavity-containing compounds such as CDs can be used as molecular templates for electrochemical polymerization/growth of conducting polymers, and (iii) explore the possibility of preparing nanosized single-stranded polymer wires using electrodes with appropriately modified surfaces. In this work we used thiolated ␤-CD molecules to modify the gold surfaces. ␤-CD has a cavity diameter of about 7.8 Å, which is large enough to serve as an anchoring site for monomer molecules such as pyrrole. 12 Experimental Pyrrole (Aldrich, 98%) was used after distillation over zinc powder and stored in...

Effects of ethoxylated ␣-naphtholsulfonic acid ͑ENSA͒ on the initial stages of tin plating have been studied on iron electrodes in an acidic stannous sulfate solution containing phenolsulfonic acid as a supporting electrolyte using potentiodynamic polarization, electrochemical quartz crystal microbalance ͑EQCM͒, scanning probe microscopy ͑SPM͒, and electrochemical impedance spectroscopy techniques. The smallest exchange current density and a larger transfer coefficient are observed at a typical ENSA concentration used in industrial plating baths, i.e., 0.013 M. The SPM imaging and EQCM measurements show that ENSA molecules form a compact structure by interacting with neighboring molecules at the iron surface, which controls the mass transport for Sn͑II͒ reduction. The EQCM studies indicate that the ENSA molecules remain stably adsorbed on the electrode surface at considerably high overpotentials. The ENSA molecules present in both the tin layers and the solution are found to slow the hydrogen evolution reaction at, as well as the corrosion process of, the tin-plated electrode, acting as an anticorrosion agent in commercial tin plating baths.

The electrochemical characteristics of Ta 2 O 5-IrO 2 electrodes prepared from different chemical compositions and coating methods were observed by using cyclic voltammetry, potentiostatic polarization, galvanostatic polarization and scanning electron microscopy. The efficiency for chloride oxidation and oxygen evolution processes was not only influenced by the chemical composition but also by the surface morphology of the oxide electrode which was susceptible to the ratio of the two components and the coating method. Ta 2 O 5 (50)-IrO 2 (50) electrodes revealed the highest catalytic activity for the chloride ion oxidation and oxygen evolution reaction because they had the largest effective surface area. The durability of the oxide electrodes in the accelerated life tests was improved as the thickness of the oxide layer increased and the ratio of [IrO 2 ] to [Ta 2 O 5 ] approached 80/20.

Effects of organic additives such as benzoic acid ͑BA͒ and poly͑ethylene glycols͒ ͑PEGs͒ on the initial stages of zinc electroplating were investigated at an iron electrode using cyclic voltammetry, energy-dispersive spectroscopy, soft X-ray absorption spectroscopy, and electrochemical impedance spectroscopy in an acidic zinc chloride solution. BA mainly contributed to the roughness control of the zinc layer with a relatively weak interaction with zinc ions. However, PEG molecules raise the overpotential for reduction of both zinc ions and protons by effectively blocking the electrode surface. Soft X-ray absorption spectroscopic results confirmed that the iron oxide layer was reduced to metallic iron by electrodeposited zinc prior to zinc bulk deposition. Impedance measurements helped reveal the roles of BA and PEG molecules during the zinc deposition on the surface and also in determining the corrosion behavior of zinc plated iron. Zinc electroplating has been widely used in the steel industry for the protection of steel products in corrosive environments. Various organic compounds have been proposed as additives for zinc electroplating and extensively studied to obtain durable, uniform, and compact zinc coatings for corrosion prevention of steel products. [1][2][3][4][5] These organic molecules or mineral impurities added to the electroplating solution were known to exert crucial influences on the qualities and corrosion characteristics of the electrodeposits.6-9 The effects of the organic molecules on the bulk electrodeposition process itself and the physical characteristics of the electrodeposited layers have been examined by voltammetric, radiometric, and electrochemical impedance spectroscopic studies. 10-16The initial electrodeposition process was reported to affect the mechanical properties of electrodeposits. 1,7 When the work function of a metal being electrodeposited is lower than that of the substrate metal, the electrodeposition may occur at a potential more positive than the equilibrium potential, a phenomenon called underpotential deposition ͑UPD͒.17 On the basis of the Kolb-Gerischer relation, 18,19 an underpotential shift (⌬E) of 0.15-0.20 V is estimated for the zinc UPD on an iron substrate. Effects of adanions, as well as the pH of the solution, on the kinetics of the zinc UPD, hydrogen adsorption, and resulting morphology of the deposit have been investigated extensively at noble metal electrodes using electrochemical and scanning tunneling microscopy techniques. 20-29 Also, zinc UPD has been studied at iron or steel electrodes in connection with the hydrogen evolution reaction. 30,31 Despite all these studies, the way in which additives affect the substrate/zinc layer/electrolyte interfaces during the initial electrodeposition on the iron electrode is poorly understood. In this work, we study the effects of the organic molecules primarily on the initial stages of zinc electrodeposition, employing various electrochemical and spectroscopic techniques. The roles played by the organic molecules ...