Pt/C containing different platinum loadings for use as electrocatalysts in alkaline PBI-based direct glycerol fuel cells

This study shows the influence of the Pt percentage in Pt catalysts (Pt/C) on their application in Direct Glycerol Fuel Cells (DGFC). Catalysts with 20, 30, 40 and 60% Pt were prepared by formic acid reduction. X-Ray Diffraction (XRD) confirmed the formation of Pt fcc nanocrystals (with average sizes between 3 and 4 nm). Thermogravimetric analysis (TGA) corroborated the Pt loadings and the Transmission Electron Microscopy (TEM) images show a homogeneous distribution of the Pt nanoparticles, with larger particles at higher Pt percentages. Electrochemical measurements reveal that higher Pt percentages promote the activity of the glycerol electroxidation reaction, resulting in lower onset potentials, higher current densities and reduced poisoning of the Pt surface. Single cell tests confirm these results, with greater maximum power density at higher Pt percentages, although the glycerol crossover effect starts to become significant in the 60% Pt/C catalyst, owing to the reduced thickness of this catalytic layer. A final product selectivity analysis indicates that tartronate is the preferential glycerol electroxidation product, along with glycerate and oxalate in lower proportions, with minor amounts of glycolate and mesoxalate. In general, a thicker catalytic layer is associated with the formation of more oxidized products.     

Morphological, optical and photocatalytic properties of TiO2–Fe2O3 multilayers

Morphological, optical and photocatalytic properties of TiO₂, Fe₂O₃ and TiO₂–Fe₂O₃ samples (formed by 1, 3 and 5 coatings) were studied. The layers were deposited on glass substrate by the sol–gel method. The catalytic activity of the samples was studied by the photodecomposition of methylene blue (MB) under visible light illumination. The FTIR results indicate that all samples present surface OH radicals that are bound either to the Ti or Fe atoms. This effect is better visualized at larger number of coatings in the TiO₂–Fe₂O₃/glass systems. Also, two mechanisms are observed during the photodecomposition of the MB.     

Different ratios of carbon sources in the fermentation of cheese whey and glucose as substrates for hydrogen and ethanol production in continuous reactors

The fermentation of glucose, cheese whey and the mixture of glucose and cheese whey were evaluated in this study from two inocula sources (sludge from a UASB reactor for swine wastewater treatment and poultry slaughterhouse) for hydrogen production in continuous anaerobic fluidized bed reactors (AFBR). For all fermentations, a hydraulic retention time (HRT) of 6 h and a substrate concentration of 5 g COD L⁻¹ were used. In glucose fermentation, the maximum hydrogen yield (HY) was 1.37 mmol H₂ g⁻¹ COD. The co-fermentation of the cheese whey and glucose mixture was favorable for the concomitant production of hydrogen and ethanol, with yields of up to 1.7 mmol H₂ g⁻¹ COD and 3.45 mol EtOH g⁻¹ COD in AFBR2. The utilization of cheese whey as a sole substrate resulted in an HY of 1.9 mmol H₂ g⁻¹ COD. Throughout the study, ethanol fermentation was evident.     

Biological hydrogen production by Anabaena sp. - Yield, energy and CO2 analysis including fermentative biomass recovery

This paper presents laboratory results of biological production of hydrogen by photoautrotophic cyanobacterium Anabaena sp. Additional hydrogen production from residual Cyanobacteria fermentation was achieved by Enterobacter aerogenes bacteria. The authors evaluated the yield of H₂ production, the energy consumption and CO₂ emissions and the technological bottlenecks and possible improvements of the whole energy and CO₂ emission chain.The authors did not attempt to extrapolate the results to an industrial scale, but to highlight the processes that need further optimization.The experiments showed that the production of hydrogen from cyanobacteria Anabaena sp. is technically viable. The hydrogen yield for this case was 0.0114 kgH₂/kg_biomass which had a rough energy consumption of 1538 MJ/MJH₂ and produced 114640 gCO₂/MJH₂. The use of phototrophic residual cyanobacteria as a substrate in a dark-fermentation process increased the hydrogen yield by 8.1% but consumed 12.0% more of energy and produced 12.1% more of CO₂ showing that although the process increased the overall efficiency of hydrogen production it was not a viable energy and CO₂ emission solution. To make cyanobacteria-based biofuel production energy and environmentally relevant, efforts should be made to improve the hydrogen yield to values which are more competitive with glucose yields (0.1 kgH₂/kg_biomass). This could be achieved through the use of electricity with at least 80% of renewables and eliminating the unessential processes (e.g. pre-concentration centrifugation).     

Natural convection in a partially open square cavity with internal heat source: An analysis of the opening mass flow

A steady buoyancy-driven flow of air in a partially open square 2D cavity with internal heat source, adiabatic bottom and top walls, and vertical walls maintained at different constant temperatures is investigated numerically in this work. A heat source with 1% of the cavity volume is present in the center of the bottom wall. The cold right wall contains a partial opening occupying 25%, 50% or 75% of the wall. The influence of the temperature gradient between the verticals walls was analyzed for Ra_e = 10³–10⁵, while the influence of the heat source was evaluated through the relation R = Ra_i/Ra_e, investigated at between 400 and 2000. Interesting results were obtained. For a low Rayleigh number, it is found that the isotherm plots are smooth and follow a parabolic shape indicating the dominance of the heat source. But as the Ra_e increases, the flow slowly becomes dominated by the temperature difference between the walls. It is also observed that multiple strong secondary circulations are formed for fluids with a small Ra_e whereas these features are absent at higher Ra_e. The comprehensive analysis is concluded with horizontal air velocity and temperature plots for the opening. The numerical results show a significant influence of the opening on the heat transfer in the cavity.     

Hydrogen production through anaerobic co-digestion of food waste and crude glycerol at mesophilic conditions

Hydrogen production from mesophilic anaerobic co-digestion of food waste (FW) and crude glycerol (GLC) was investigated in this study. Batch experiments were carried out at 35 °C for 36 h to assess the effect of supplementation of different glycerol concentrations (1%, 3% and 5% (v/v)) on dark fermentation of FW. The maximum hydrogen yield (180 mLH₂/gVS) was obtained at 5% GLC while the maximum specific production rate (around 13 mLH₂/(gVS.h)) was similar for all experiments with glycerol addition. Besides contributing to increase H₂ productivity, the presence of glycerol reduced the microorganisms acclimation time (Lag phase) in comparison to the control tests conducted without this co-substrate. In addition, the increment of glycerol concentration also enhanced volatile fatty acids generation and favoured the production of 1,3-propanediol (1,3-PDO). In the experimental conditions studied (i.e., 1–5% (v/v) of GLC), the results revealed that co-digestion of FW and GLC is promising and can be potentially used to maximize energy production while contributing to the management and treatment of these wastes.     

Is there an association between lateral preference and delinquent behavior?

Results of recent research suggests an association between left lateral preference and delinquent behavior. In this study the lateral preferences of 881 seven-year-old children were determined using behavioral indicators of hand and foot use. Mixed-handedness was associated with parent-reported problem behavior scores and self-reported delinquency scores at ages 13 and 15. However, preference for left hand and foot use was found to be unrelated to the delinquency measures. The distribution of lateral preferences in an identified delinquent group was not significantly different from the distribution in the sample remainder. The lack of an association between left preference and delinquency may be accounted for by an increased cultural acceptance of individual preference. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Vibrational properties and infrared dielectric features of Gd2CoMnO6 and Y2CoMnO6 double perovskites

Gd₂CoMnO₆ and Y₂CoMnO₆ double perovskite ceramics were obtained from the polymeric precursors method and investigated by X-ray diffraction, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), Raman and Fourier Transform Infrared (FTIR) spectroscopies. Our results show that these samples present similar structural and vibrational characteristics that are fully compatible with a monoclinic structure belonging to the P2₁/n space group, with ordered Co²⁺ and Mn⁴⁺ cations. Infrared-reflectivity spectroscopy was employed to investigate the polar phonon features and to determine the intrinsic dielectric response of the materials. In particular, the extrapolated dielectric constants at the lower frequency infrared limit showed to be independent on the particle size, and were determined as ${\epsilon \prime }_{\mathit{intr}}\approx 17.8$ and 16.0, for Gd₂CoMnO₆ and Y₂CoMnO₆, respectively. Otherwise, it is shown that for smaller RE radius the FTIR bands become more evidenced, due to a higher octahedral rotation and lower $<$Co-O-Mn$>$ angle into the distorted monoclinic structure.     

Co-authorship networks and research impact in large research facilities: benchmarking internal reports and bibliometric databases

Scientometrics - In this paper, we address the main differences of the scientific production between internal and external researcher groups of a synchrotron radiation facility. Through the...