Reinaldo Simões Gonçalves

Room temperature dialkylimidazolium ionic liquid-based fuel cells

The non-Bronsted acid–base room temperature imidazolium ionic liquids, such as 1-n-butyl-3-methylimidazolium tetrafluoroborate (BMI.BF4), are out-standing electrolytes for fuel cells. A 67% overall cell efficiency is achieved using these liquids as supporting electrolytes for a commercially available alkaline fuel cells (AFC) at room temperature operating with air and hydrogen at atmospheric pressure.

Electrochemical studies of propargyl alcohol as corrosion inhibitor for nickel, copper, and copper/nickel (55/45) alloy

Abstract The electrochemical behaviour of copper, nickel and copper/nickel (Cu55/Ni45) alloy in 0.50 M H2SO4 in the absence and presence of propargyl alcohol has been studied. The results indicate that the electrochemical behaviour of the copper/nickel alloy is similar to that of nickel. The interaction between the electrode surface and the organic compound is a relatively fast process and depends on the adsorption potential and alcohol concentration. Anodic currents associated with the electrooxidation of the metals decrease in the presence of propargyl alcohol. Differences in inhibition experience by the three electrodes are discussed in terms of cyclic voltammetry, potentiometry and impedance measurements.

Preparation, cation-anion interactions and physicochemical properties of ether-functionalized imidazolium ionic liquids

A set of 1-alkyl ether (and 1-alkyl)-3-methylimidazolium ionic liquids 2-4 ([CxOyMIm]+[Anion]- or [CxMIm]+[Anion]-, where MIm = 3-methylimidazolium; CxOy = 1-alkyl ether, C7O3 = -(CH2)2O(CH2)2O(CH2)2OCH3 (A), C3O1 = -(CH2)2OCH3 (B); Cx = 1-alkyl, C10 = C10H21 (C), C4 = C4H9 (D); and [Anion]- = H3CSO3- (2), BF4- (3) or PF6- (4)) was prepared and characterized. The cation-anion hydrogen bonding strength showed to be mainly anion dependent and decreased in the order H3CSO3- > BF4- > PF6-. All methanesulfonate ionic liquids 2 possessed a strongly deshielded H2 imidazolium ring proton. 1-Alkyl ether functionalized ionic liquids showed higher densities in comparison to their 1-alkyl equivalents. The salts 2a-b, 3a-d and 4a-b are room-temperature ionic liquids. All 1-alkyl ether functionalized ionic liquids (except 4b) are completely amorphous. The widest liquid ranges were obtained with the tetrafluoroborate ionic liquids due to their late solidification and excellent thermal stability. These data provide important information for the understanding of their application scope and the preparation of task-specific ionic liquids.

Electrochemical Behavior of Vitreous Glass Carbon and Platinum Electrodes in the Ionic Liquid 1-n-Butyl-3-Methylimidazolium Trifluoroacetate

The 1-n-butyl-3-methylimidazolium trifluoroacetate ionic liquid electrochemical windows have been investigated at vitreous carbon and platinum disc electrodes under static and dynamic conditions. The electrochemical window abruptly decreases by changing vitreous carbon (4.50 V) by platinum electrode (2.50 V). Electrode rotation and potential sweep rate did not affect the current-potential profiles but alter the current values of both anodic and cathodic peaks. The adsorption of imidazolium cation involved in the charge transfer process during the cathodic sweep rate was evidenced, mainly at low electrode rotation.

Electrochemical investigation of ascorbic acid adsorption on low-carbon steel in 0.50 M Na2SO4 solutions

Abstract The influence of the presence of ascorbic acid on the electrochemical behavior of low-carbon steel in 0.50 M Na 2 SO 4 aqueous solutions is described. The data confirm the inhibitory effect of ascorbic acid on the corrosion processes of this metal. It was observed that the incidence of monochromatic light may affect the electrochemical behavior of the electrode in this medium as well as the interaction between the electrode and ascorbic acid. The action of light is attributed to the complex interaction of several photosensitive phenomena.

Relato de uma experiência: recuperação e cadastramento de resíduos dos laboratórios de graduação do Instituto de Química da Universidade Federal do Rio Grande do Sul

An experience aiming to promote a residue interchange and recovery between the teaching laboratories of the Chemistry Institute of this University is described. At the present, several residues interchange have already appeared as advantageous. To make the work easier, a software has been developed in order to keep a record of all the residues generated by the teaching laboratories. Standard labels have been developed for the residues in order to organize them. The software and the label design are described.

Anilinepropylsilica xerogel used as a selective Cu (II) adsorbent in aqueous solution

The metal ion adsorption properties of the microporous hybrid anilinepropylsilica xerogel were studied using divalent copper, zinc, and cadmium ions in aqueous solutions in concentrations ranging from 10(-4) up to 5x10(-3) moll(-1). At low concentrations the surface of the solid phase presents selectivity for Cu (II), even in competitive conditions. This preferential sorption ability for copper in relation to zinc and cadmium ions was interpreted by considering the xerogel morphology.

Alcoholic Mentha extracts as inhibitors of low-carbon steel corrosion in aqueous medium

This paper presents experimental evidence of the ability of alcoholic Mentha extracts to inhibit the corrosion of low-carbon steel in aqueous acid solutions. Alcoholic extracts of Mentha spicata L., Mentha x gentilis L., Mentha crispa L., Mentha piperita L., and Mentha x piperita L. were tested. The corrosion inhibition capability of these extracts was confirmed by means of weight loss experiments, cyclic voltammetry, chronoamperometry, polarization curves, and electrochemical impedance spectroscopy.

Assessment of caffeine adsorption onto mild steel surface as an eco-friendly corrosion inhibitor

The adsorption and corrosion-inhibition properties of caffeine as an eco-friendly corrosion inhibitor for mild steel in acid medium were investigated by electrochemical and spectroscopic techniques. Polarization experiments indicated that caffeine behaves as a cathodic-type inhibitor. Impedance data showed that surface coverage increased with caffeine concentration in the range of 1.0 to 10.0 mmol L-1. The maximum inhibition efficiency obtained was 92.4%. The adsorption of the corrosion inhibitor was consistent with the Frumkin adsorption isotherm with a free energy of adsorption of -66.1 kJ mol-1. Contact angle measurements revealed the formation of a hydrophobic protective film, while scanning electron microscopy, energy dispersive spectroscopy and fluorescence experiments clearly verified the presence of caffeine on the surface.

Evidence of a polymeric film formation from furfural electrooxidation on platinum platinized electrode in acetonitrile

Abstract A polymeric film formed from furfural (2‐furancarboxaldehyde) dissolved in acetonitrile was observed on Pt/Pt electrodes. Three different electrochemical methods such as cyclic voltammetry (CV), chronopotentiometry, and chronoamperometry were used to grow the film. The polymeric film was perfectly visible on the electrode surface, however, scanning electron microscopy (SEM) photographs were taken in order to confirm the presence of the film. The structure of the polymer according to the data obtained from IR spectroscopic data is also presented. The influence of the film on the electrochemical behavior of the platinum electrode was characterized by comparing the I(E) curves in aqueous 0.50 mol/L H2SO4 solutions. After recovering the voltammograms confirm the modification of the electrode surface. Basically, a strong inhibition of hydrogen reduction/oxidation was observed in the cathodic potential range. However, at potentials more positive than 1.10 V (SCE) the stability of the film was poor, suggesting a degradation of the polymer. The electrochemical impedance spectroscopy (EIS) responses of modified Pt/Pt electrodes coated with polyfurfural were also placed in aqueous sulfuric acid. The presence of the film on the electrode surface was characterized by a capacitive behavior at low frequencies.