Portugaliae
Electrochimica Acta

Extensive quantities, like electrode reaction rates and double layer parameters, have to be referred to the unit real surface of the electrode, in order to compare the activity of different electrode materials and / or different preparation methods for the same material. The purpose of this paper is to review three methods usually used for the estimation of the real surface of CO3O4 and NiCO2O4 thin film electrodes. Two of them, capacitance ratio and voltammetric charge, are based on the voltammetric technique whereas the third one, Zn2+ ion adsorption (ZIA), is based on the ionic interaction at the solid-liquid interface. The applicability, advantages and limitations of the three methods are compared.

The influence of some chalcones on the corrosion of nickel in 1 N nitric acid solution has been studied using weight loss and galvanostatic polarization techniques. In general, at constant acid concentration, inhibitor efficiency increases with increase of concentration of inhibitor and decreases with rise in temperature. Polarization studies reveal that the compounds behave as cathodic inhibitors. The effect of temperature on corrosion inhibition has been studied and activation energy has been evaluated. The adsorption of the inhibitor on the nickel surface is found to obey the Frumkin adsorption isotherm. Some thermodynamic parameters are calculated and discussed.

Propylene carbonate (PC) and -butyrolactone (GBL) are important dipolar aprotic solvents good to prepare electrolyte solutions of lithium perchlorate applicable to rechargeable high energy batteries, as we have shown before [1-5]. In this work solution conductances of LiClO4 and (C2H5)4NBr in those solvents were measured at temperatures ranging from -30 ºC to +25 ºC. Limiting molar conductivities and association constants were evaluated through Viana and Calado [6] and Fuoss and Hsia’s equations [7]. Some thermodynamic functions resulting from (KA, T) variations are obtained and the results are discussed on this basis. The accuracy and precision of the results is high and they are where possible comparable to others previously published [8, 9].

Octadecanethiol self-assembled monolayer (OCSAM), which was first employed as one sensitizer for TiO2 nanoporous film electrode in the oxidation of methanol, was firstly investigated using electrochemical and photoelectrochemical methods. The photocurrent generated by using TiO2 nanoporous film electrode modified by OCSAM (18SH/ TiO2) is about 1.95 times larger than that without modification. In addition, the maximum absorption peak has shifted towards the infrared region for about 30nm when the TiO2 nanoporous film electrode modified with OCSAM. This paper has testified that the increased photocurrent could not be attributed to the photooxidation of octadecanethiol or the ethanol solvent simply. It was proposed that the change of surface structure of TiO2 nanoporous film electrode should be responsible for the phenomenon in some degree.

The surface analysis using interferometry studies clearly indicates that the oxidation cycling at high frequency at aluminium electrode in the 0.1M NaClO4 containing 10 mM sodium tetraphenylborate solution yields selective dissolution of faces other than (111) by forming pyramidal shape voids that is not due to the simultaneous dissolution and redeposition as in the case of Pt. It is also confirmed that surface smoothing and flattening on the aluminium surface is due to flattening process and the formation of voids are due to electrochemical dissolution.