Wen-Bin Cai

Dynamics of the dissolution of an underpotentially deposited Cu layer on Au(111): a combined time-resolved surface-enhanced infrared and chronoamperometric study

It is well known that an ordered phase consisting of 2/3 monolayer (ML) of Cu and 1/3 ML of sulfate is formed by the underpotential deposition of Cu on Au(111) in sulfuric acid. Dynamic processes involved in the dissolution of the ordered phase for a potential step have been investigated by time-resolved surface-enhanced infrared absorption spectroscopy (SEIRAS) and chronoamperometry. The results demonstrate that the dissolution occurs through two successive steps. The initial step involves the desorption of 1/3 ML of Cu and 1/3 ML of sulfate via a Langmuir-type kinetics and the remaining 1/3 ML of Cu is desorbed in the subsequent step via a nucleation-and-growth kinetics. The observation is partly consistent with dynamic Monte Carlo simulations reported in the literature.

A comparison of surface-enhanced infrared and surface-enhanced Raman spectra of pyrazine adsorbed on polycrystalline gold electrodes

The adsorption of pyrazine at a polycrystalline Au film electrode has been investigated using in situ surface-enhanced infrared absorption spectroscopy (SEIRAS), chronocoulometry, and ac impedance. Combining the SEIRA data and the thermodynamic data (the surface charge density of the electrode and the relative Gibbs surface excess of pyrazine), pyrazine was found to adsorb on the surface with a vertical end-on configuration via one N atom. The SEIRA spectra were compared with published surface-enhanced Raman (SER) spectra of pyrazine in order to clarify the reason for the breakdown of the Raman selection rule in the SER spectra. The activation of originally Raman-forbidden modes in the SER spectra is well explained by a photo-driven charge-transfer mechanism. The charge-transfer is deduced to be from filled metal states near the Fermi level to the first and second excited states of pyrazine. It is emphasized that the comparative SEIRA and SER studies are important for a better understanding of the electrochemical interface.

Surface-Enhanced Infrared Spectroscopic Study of a CO-Covered Pt Electrode in Room-Temperature Ionic Liquid

ATR-SEIRAS is extended for the first time to study potential-induced surface and interface structure variation of a CO-covered Pt electrode in a room-temperature ionic liquid of N-butyl-N-methyl-piperidinium bis((trifluoromethyl)sulfonyl)imide (or [Pip14][TNf2]). Owing to a wide effective potential window of [Pip14][TNf2], a gradual conversion from bridged COad (COB) to terminal COad (COL) is observed in response to positively going potentials, suggesting that [Pip14](+) may be involved in a strong electrostatic interaction with the COad. This site conversion enables the ratio of the apparent absorption coefficient of COL to that of COB to be determined. Also, the spectral results reveal the potential-dependent COad frequency variations as well as the potential-induced interfacial ionic reorientation and movement at the Pt/CO/[Pip14][TNf2] interface.

Electrochemical studies of polyaspartic acid and sodium tungstate as corrosion inhibitors for brass and Cu30Ni alloy in simulated cooled water solutions

Purpose – The aim of this paper is to study the inhibition effect of environmentally friendly inhibitors; polyaspartic acid (PASP), Na2WO4 and the complex of PASP and Na2WO4 for brass and Cu30Ni alloy (B30) corrosion in simulated cooled water solutions.Design/methodology/approach – The inhibiting effect was investigated in simulated cooled water solutions by potentiodynamic polarization (DC) and electrochemical impedance spectroscopy.Findings – The results indicated that PASP and Na2WO4 both had an inhibition effect. A desirable inhibition effect was shown for brass and B30 corrosion at a PASP concentration of 15u2009mg/L. The best inhibition effects for Na2WO4 appeared at 10u2009mg/L for B30 corrosion and at 20u2009mg/L for brass, respectively. The combination of PASP and Na2WO4 showed a synergistic effect. The optimum ratio of PASP to Na2WO4 was 6:1 at the total inhibitor concentration of 20u2009mg/L.Originality/value – This paper has for the first time showed that the two environmentally friendly inhibitors PASP and N...