TiO2 Synthesis by Pechini Method and Application in Dye-Sensitized Solar Cells

Dye-sensitized solar cells (DSSC) are devices to solar energy conversion, which present low production costs and high photoelectrochemical stability. The aim of this study was to investigate the synthesis of TiO2 by Pechini methodology, using C12H28O4Ti and TiCl3 as precursors, and their application in solar cell sensitized by N719 dye. The characterization techniques employed were Scanning Electron Microscopy (SEM), UV-VIS Spectroscopy, X-ray diffraction (XRD), photochronoamperometry, j-V Curves and EIS plots. The results demonstrated a high crystallinity and surface area to particles obtained with C12H28O4Ti as precursor. The highest photoconversion energy efficiency reached was to TiO2 using C12H28O4Ti with PCE= 4.17±0.13% with photoelectrochemical parameters of jsc= 5.53 ±0.08, Voc= 0.78±0.07 FF=0.58±0.05 and less resistive to charge transport with τe= 53 ms. DOI: http://dx.doi.org/10.17807/orbital.v13i2.144

Study of the Influence of Nb2O5 in ZnO Solar Cells

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%. DOI: http://dx.doi.org/10.17807/orbital.v10i3.110

Application of Zinc Oxide Nanospheres for Hybrid Solar Cell

Poly(3-alkylthiophenes), P3AT, are organic polymers formed by conjugate structures with conductive properties. Zinc oxide (ZnO) has been used as an electron acceptor in hybrid solar cells because it offers electron transport properties and can be synthesized by methods in which the variation of synthesis parameters allows morphological control. Different ZnO morphologies allow for distinct properties in terms of electronic transport at the interface of solar cells. ZnO particles were synthesized by the co-precipitation method. ZnO films were deposited by spin-coating in Fluorine Tin Oxide (FTO) and then immersed in solutions containing poly (3-hexylthiophene) (P3HT) or poly (3-octylthiophene) (P3OT) polymers. The cell was assembled in the form of a sandwich consisting of: FTO/ZnO,P3AT/Iˉ,I3ˉ/Pt/FTO. UV-vis measurements were performed for bandgap calculation, scanning electron microscopy (SEM), X-ray diffraction (XRD), and J-V curves. The ZnO/P3HT cell presented the best values of J, V and η, indicating an improvement in the electronic transfer processes, with a value of η = 0.56%. DOI: http://dx.doi.org/10.17807/orbital.v13i2.145

Influence of Deposition Methodology and Heating Treatment on Dye Sensitized Solar Cell with Natural Extract

In this study, it was investigated the photovoltaic parameters of Dye Sensitized Solar Cells (DSSC) and the thin coating morphology of TiO2 by Doctor Blading and Spin Coating methods, sintered at 450 ºC and 450 ºC with a heating rate of 0.4 ºC s-1, using a natural dye extract from Hibiscus. These properties were studied by scanning electron microscopy (SEM), photochronoamperometry and curves j-V. It was demonstrated that all solar cells produced are photosensitive with an excellent charge injection. The cell with a better energy conversion (jsc = 0.53 mA cm-2; Voc= 0.471 V and FF= 0.518), uniform and flawless morphology was obtained to cell coated by Doctor Blading method, with a heat treatment of 450 ºC/0.4 ºC s-1. DOI: http://dx.doi.org/10.17807/orbital.v10i3.110

Ascorbic Acid as Antioxidant for Soybean Biodiesel

The intensive use of fossil fuels has had consequences coming from the instability of the reserves, due to the finitude of the resource, as well as the environmental impacts that the use of these fuels entails, such as the increasement of greenhouse gases. In this way, a promising alternative found to attenuate such problems is the production of biofuels, such as biodiesel, in which are used raw materials from renewable sources. They contribute to decrease dependence on oil and reduce the greenhouse effect. However, after biodiesel is produced, it is subject to degradation reaction when in contact with air, light, and temperature, which promotes the reduction of its quality. To slow down the degradation reaction, antioxidants are added to the biodiesel, providing greater oxidation stability. Antioxidants are substances that retard oxidation and can be natural, such as ascorbic acids or synthetic substances. Thus, this work aimed to evaluate the efficiency of ascorbic acid as an antioxidant in soybean biodiesel. Oxidative stability tests were performed and it was observed that the best concentration of ascorbic acid in soybean biodiesel, as antioxidant, is 27.5 g L-1. DOI: http://dx.doi.org/10.17807/orbital.v10i3.109

The influence of Annona muricata L. peel extract as a potent source of natural antioxidant on soybean oxidation stability: A influência do extrato de Annona muricata L. peel como uma potente fonte de antioxidante natural na estabilidade da oxidação da soja

Antioxidants are an alternative to prevent or retard biodiesel degradation. Soursop (Annona muricata L.) is a native tropical fruit with important antioxidant activity, besides high concentration of phenolic compounds. Peels form about 20 % of the soursop fruit composition and are usually discarded as a waste product. In this study the antioxidant potential of different peel extracts was evaluated by oxidative stability when used as an additive into soybean biodiesel. All samples were analyzed by the Rancimat® 873, using 32 experimental design. The tests were performed with biodiesel B100 with solutions extracted in different conditions, such as pH and residue concentrations. Results demonstrated that all experiments were able to increase significantly the induction period (IP), when compared to a pure biodiesel control sample, and showed similar efficiency with synthetic antioxidants (BHT). Among all experiments, each neutral and alkaline extractions presented induction periods over 8 h, achieving and surpassing the minimum allowed by European standard. However, the highest IP was found to be 10.30 h, with 3 g L-1 in neutral extraction.  Results corroborate that soursop peel has a high antioxidant capacity and efficiency to improve the oxidation stability, and could be used as an inexpensive natural antioxidant to biodiesel

Optimisation of the alcoholic fermentation of aqueous jerivá pulp extract

The objective of this research is to determinate the optimum conditions for the alcoholic fermentation process of aqueous jerivá pulp extract using the response surface methodology and simplex optimisation technique. The incomplete factorial design 3³ was applied with the yeast extract, NH4H2PO4 and yeast as the independent variables and the alcohol production yield as the response. The regression analysis indicated that the model is predictive, and the simplex optimisation generated a formulation containing 0.35 g L-1 yeast extract, 6.33 g L-1 yeast and 0.30 g L-1NH4H2PO4 for an optimum yield of 85.40% ethanol. To validate the predictive equation, the experiment was carried out in triplicate under optimum conditions, and an average yield of 87.15% was obtained. According to a t-test, no significant difference was observed (on the order of 5%) between the average value obtained and the value indicated by the simplex optimisation technique.The objective of this research is to determinate the optimum conditions for the alcoholic fermentation process of aqueous jerivá pulp extract using the response surface methodology and simplex optimisation technique. The incomplete factorial design 3³ was applied with the yeast extract, NH4H2PO4 and yeast as the independent variables and the alcohol production yield as the response. The regression analysis indicated that the model is predictive, and the simplex optimisation generated a formulation containing 0.35 g L-1 yeast extract, 6.33 g L-1 yeast and 0.30 g L-1 NH4H2PO4 for an optimum yield of 85.40% ethanol. To validate the predictive equation, the experiment was carried out in triplicate under optimum conditions, and an average yield of 87.15% was obtained. According to a t-test, no significant difference was observed (on the order of 5%) between the average value obtained and the value indicated by the simplex optimisation technique.

CARACTERIZAÇÃO DE FILMES FINOS A BASE DE ESTANHO DOPADOS COM NIÓBIO PARA CÉLULAS SOLARES

As células fotovoltaicas constituídas de filmes finos de óxidos metálicos são promissoras para a conversão de energia solar em energia elétrica devido ao custo reduzido e as vantagens ambientais.  O objetivo deste trabalho é a produção de filmes finos a base de estanho pelo método Pechini visando à aplicação em células solares. Os filmes obtidos foram caracterizados por Microscopia Eletrônica de Varredura (MEV), Espectroscopia de Energia Dispersiva (EDS), Difração de Raios X (DRX) e Espectroscopia de Impedância Eletroquímica (EIE). Os resultados de MEV e EDS indicaram que resinas com viscosidade alta geram filmes pouco homogêneos. Os diagramas de impedância indicaram que o filme sobre o substrato de ITO aumenta a resistência do sistema