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Renewable energy sources have received much attention in recent years due to concerns about global climate and environmental changes. Solar energy appears to be a promising alternative, especially dye-sensitized solar cells (DSSC), which, according to the literature, can achieve a power conversion efficiency in excess of 11%, depending on the semiconductor oxide used in their fabrication. The aim of this paper is to investigate the performance of DSSCs using cerium oxide (CeO2), titanium oxide (TiO2), and commercial dye N719. CeO2 was obtained using the Pechini and precipitation methods. The characterization techniques employed were x-ray diffraction, Raman spectroscopy, scanning electron microscopy, ultraviolet-visible spectroscopy, dynamic light scattering, and photoelectrochemical measurements. The results indicate that the efficiency of the DSSC CeO2/TiO2 obtained using the precipitation method was about 20% higher than that of the DSSC TiO2. [ABSTRACT FROM AUTHOR]

The solar cells of semiconductors oxides have been largely studied. The zinc oxide (ZnO) and niobium oxide (Nb2O5) used in this work presented important physical-chemical characteristics in use of photovoltaic devices. The Nb2O5 presents the capacity of minimizing effects of charge recombination in the process of energetic conversion of solar cells. The oxides used in this work were characterized by the technique X-ray diffraction. The solar cells containing 5% of Nb2O5 presented of best results in a relationship of the electron transfer process, reaching the efficiency of 0.42%. [ABSTRACT FROM AUTHOR]

Hybrid solar cells of semiconductor oxides and conductive polymers have been broadly studied. Poly(3-octylthiophene) (P3OT), is an organic polymer formed by conjugated structures with conductive properties, photoluminescence, a relatively high charge mobility and stability. Zinc oxide (ZnO) has been used as an electron acceptor in this cell type because it offers great electron transport properties, simple manufacturing techniques, non-toxicity, variation and morphologic control. Different ZnO morphologies allow distinct properties in terms of electronic transport in solar cell interfaces. The objective of this paper was to evaluate whether ZnO with its different morphologies can improve the anchorage of P3OT and influence the conductive properties of hybrid solar cells of ZnO/P3OT. ZnO particles were synthetized by co-precipitation with Zn(NO)·6HO in concentrations of 0.05, 0.10 and 0.15 mol L. The morphology was evaluated by scanning electron microscopy (SEM), and the suspension was evaluated by thermogravimetric analysis and differential scanning calorimetry and X-ray diffraction. Cells containing the working electrode (ZnO/P3OT) were evaluated by open circuit potential (V) and electrochemical impedance spectroscopy (EIS). The SEM images showed three morphologies: spherical ZnO (ZnOE), hexagonal ZnO (ZnOH) and ZnO without defined morphology (ZnOM) due to the variation of the precursor salt concentration. Cells with different morphologies presented medium values of V = −0.438 ± 0.027 V. The EIS indicated that ZnOM/P3OT cells have lower values of charge transfer resistance and higher values of capacitance at intermediate frequencies. ZnOM/P3OT solar cells presented the best results in relation to the electron transfer processes. [ABSTRACT FROM AUTHOR]

The adsorption of organic substances in metals and in different media has been attributed to different effects, such as the carbon chain size, type or number of hetero-atom in the molecule structure, reactivity, the steric effect, among others. The objective of this work is to study the electrochemical indole behavior for AISI 430 stainless steel (SS), when changing the study media from H2SO4 1 mol L-1 to HCl 1 mol L-1. The experimental techniques used are as follows: the open-circuit potential, anodic and cathodic potentiodinamic polarization, electrochemical impedance spectroscopy, optical microscopy and scanning electron microscopy. These results suggest that the adsorption of indole in the presence of SO4-2 is lower than in the medium containing Cl, which is justified by the indole action as a weak acid, because it has only a single pair of electrons, which is displaced and takes part in the π-electron aromatic system; thus the first step of the indole reaction in acid media is the protonation and generation of an indole cation. [ABSTRACT FROM AUTHOR]

Self-assembly molecules (SAM - Self Assembly Monolayer) are corrosion inhibitors, due to their capacity to organize on surfaces, forming thin films. SAM presents a high affinity to aluminum oxide. However, the interactions between the oxide layer and SAM are not always satisfactory; therefore the oxide formed on the surface presents heterogeneities that hinder SAM film formation. The aim of this work was to study the corrosion protection of aluminum AA 2024-T3 associated with SAM, after treatment with alkaline degreasing. The electrochemical characterization was carried out by electrochemical impedance spectroscopy and anodic potentiodynamic polarization in Na2SO4 0,5 mol.L-1 in pH 4,0. The superficial morphology was investigated by optic microscopy. The results showed that SAM promoted greater aluminum protection when this was pretreated with degreasing. [ABSTRACT FROM AUTHOR]

Amino acids and self assembled monolayers (SAM's) have been studied as to their inhibiting action on the corrosion of metallic materials. The objective of this work is to study the electrochemical behavior of the cisteincisteine, the diphosfonate and the mixture of both in inhibiting the action of corrosion on stainless steel 304 in HCl 1 molL-1. As the following techniques were used: open circuit potential (OCP), potenciostatic anodic polarization (AP), chronoamperometry (CA), electrochemical impedance spectroscopy (EIS) and optical microscopy (OM). The results of CA showed that cisteine has a double effect, catalytic and inhibiting, in function of the immersion time of the metallic part in the electrolytic solution. AP curves have shown lesser current density for the system containing cisteine + diphosfonate, suggesting an inhibiting synergic action. These results have been confi rmed by EIS and OM. [ABSTRACT FROM AUTHOR]

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