A study on the electrocatalytic performances of nickel–cobalt alloys for hydrogen evolution in alkaline media has been carried out. After preparing, by electrodeposition on aluminium net supports, ...Ni–Co alloys of various compositions ranging from 0 to 100% Ni, the alloys were examined by polarization measurements, to evaluate their discharge potential and Tafel parameters. Moreover a durability test has been done on the alloys showing, among all, the best performance. The hydrogen over-potential appears to be lower in the case of Ni concentrations ranging between 35 and 59 weight percent. The synergism among the nickel catalytic properties, having low hydrogen over-potential and high hydrogen adsorption of cobalt, is best realized in this conditions and allow obtaining a largest value of exchange current density.
•Indium electrodeposition on Cu, Ti and Al supports by using sulfate solution.•Voltammetric analysis of indium electrodeposition for Cu, Ti and Al supports.•Determination of electron transer rate ...constant (k0) for inidum electrodeposition.•Routhness factor determination and Tafel analisys.•Higher electrocatalytic response for indium reduction on Cu followed by Ti and Al.
Indium electrowinning process from sulfate solution on copper, titanium and aluminum cathodes (Cu, Ti and Al) were studied using the methods of cyclic voltammetry (CV) and chronoamperometry (CA). Voltammogram features indicated the irreversible behavior of indium discharge on each cathode. The heterogeneous charge transfer rate constant (k0) has been evaluated on Cu, Ti and Al cathodes and their values were 7.1·10−5 cm/s, 6.2·10−5 cm/s and 5.4·10−5 cm/s, respectively. The indium ions electro-reduction seems to be quite different on these diverse cathodic supports: a nucleation process appears on Cu and Al cathodes, while is absent on Ti cathode due to the hydrogen evolution overlapping at high cathodic overpotentials. CV and CA techniques allowed to calculate the diffusion coefficient (D0) of indium ion in sulfate solution. Furthermore, calculating the roughness coefficient (φ) by CV technique on each metal surface, it was possible to establish the real surface area of Cu, Ti and Al cathodic supports. The charge transfer coefficient values (α) calculated by Tafel curves agreed those obtained by CV results, while the k0 value and the exchange current density (i0) showed a similar trend for each cathode. By these results, the exchange current density was equal to 1.20 mA/cm2, 0.30 mA/cm2 and 0.075 mA/cm2 for Cu cathode Ti and Al cathodes, respectively. The findings of this investigation can provide an understanding of the indium electrowinning process on three different support electrodes (Cu, Ti and Al) from sulfate solution.
•Electrode modification by electrosynthesized PEDOT as sensing layer.•Analysis does not require a pretreatment of the sample.•Standard additions method on real samples prevents interferences of other ...compounds.•Linearity range wider than methods already present in literature.
A novel method using PEDOT (poly(3,4-ethylenedioxy) thiophene) modified electrode was developed for the determination of caffeic acid (CA) in wine. Cyclic voltammetry (CV) with the additions standard method was used to quantify the analyte at PEDOT modified electrodes. PEDOT films were electrodeposited on Platinum electrode (Pt) in aqueous medium by galvanostatic method using sodium poly(styrene-4-sulfonate) (PSS) as electrolyte and surfactant. CV allows detecting the analyte over a wide concentration range (10.0nmoll−1–6.5mmoll−1). The electrochemical method proposed showed good statistical and analytical parameters as linearity range, LOD, LOQ and sensitivity.
In this study Ni–Co alloys have been activated during hydrogen electrochemical production by adding Mo ions into the alkaline electrolyte. After dissolving different amounts of sodium molybdate in ...the Na(OH) electrolyte, Ni–Co alloys were used as cathodes for hydrogen evolution reaction. Afterwards a comparison between hydrogen overvoltage measured on Ni–Co alloys with and without in situ activation has been made. The in situ activation clearly shows an improvement of electrocatalytic properties of Ni–Co alloys for hydrogen evolution reaction. Depending on the alloy the best conditions are reached with different amounts of sodium molybdate in the electrolyte. The values of exchange current density for Ni–Co alloys without Mo, are an average of about 4.1 10−6 A/cm2, while by using in situ activation, these values are about 3.5·10−4 A/cm2. Therefore, exchange current density presents a value nearly one hundred-fold higher when molybdate ions are present in solution. Moreover, two Tafel slope values have been determined for HER on Ni–Co alloys with and without Mo in situ activation. Those Tafel slope values are different, so as their range of both overvoltage and current density, probably highlighting a different kinetic mechanism.
•The in situ activation with Mo improves Ni–Co alloys as catalysts for alkaline HER.•Electrocatalytic activity of an alloy is also related to its composition.•Molybdenum presence gives to the electrode electrochemical stability.
Xylanase and β-glucanase combination (XG) hydrolyzes soluble non-starch polysaccharides that are anti-nutritional compounds. This study aimed to evaluate the effects of increasing levels of XG on ...intestinal health and growth performance of nursery pigs.
Forty pigs (6.5 ± 0.4 kg) were assigned to 5 dietary treatments and fed for 35 d in 3 phases (11, 9, and 15 d, respectively). Basal diets mainly included corn, soybean meal, and corn distiller's dried grains with solubles, contained phytase (750 FTU/kg), and were supplemented with 5 levels of XG at (1) 0, (2) 280 TXU/kg xylanase and 125 TGU/kg β-glucanase, (3) 560 and 250, (4) 840 and 375, or (5) 1,120 and 500, respectively. Growth performance was measured. On d 35, all pigs were euthanized and jejunal mucosa, jejunal digesta, jejunal tissues, and ileal digesta were collected to determine the effects of increasing XG levels and XG intake on intestinal health.
Increasing XG intake tended to quadratically decrease (P = 0.059) viscosity of jejunal digesta (min: 1.74 mPa·s at 751/335 (TXU/TGU)/kg). Increasing levels of XG quadratically decreased (P < 0.05) Prevotellaceae (min: 0.6% at 630/281 (TXU/TGU)/kg) in the jejunal mucosa. Increasing XG intake quadratically increased (P < 0.05) Lactobacillaceae (max: 40.3% at 608/271 (TXU/TGU)/kg) in the jejunal mucosa. Increasing XG intake quadratically decreased (P < 0.05) Helicobacteraceae (min: 1.6% at 560/250 (TXU/TGU)/kg) in the jejunal mucosa. Increasing levels of XG tended to linearly decrease (P = 0.073) jejunal IgG and tended to quadratically increase (P = 0.085) jejunal villus height to crypt depth ratio (max: 2.62 at 560/250 (TXU/TGU)/kg). Increasing XG intake tended to linearly increase the apparent ileal digestibility of dry matter (P = 0.087) and ether extract (P = 0.065). Increasing XG intake linearly increased (P < 0.05) average daily gain.
A combinational use of xylanase and β-glucanase would hydrolyze the non-starch polysaccharides fractions, positively modulating the jejunal mucosa-associated microbiota. Increased intake of these enzyme combination possibly reduced digesta viscosity and humoral immune response in the jejunum resulting in improved intestinal structure, and ileal digestibility of nutrients, and finally improving growth of nursery pigs. The beneficial effects were maximized at a combination of 550 to 800 TXU/kg xylanase and 250 to 360 TGU/kg β-glucanase.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Nickel–cobalt alloys having settled composition can be produced by electrolysis after optimising process operative conditions. In this work nickel–cobalt coatings on 1050 Al net, obtained by ...electrodeposition under galvanostatic conditions, were investigated. Ni–Co coatings were electrowon, from an acidic sulphate bath containing 40
g/L Ni and Co in the range 0.1–16
g/L, at 60
°C temperature and 300
A/m
2 average current density. The experimental results highlight a linear correlation between bath and deposit Co/Ni ratio, with slope change for Co concentration in the electrolyte higher than 3
g/L. Morphology, structure and electrochemical properties are strictly correlated among themselves and with the composition of the coating.
► Ni–Co coatings with settled composition were produced by electrolysis. ► Linear correlation between bath and deposit Co/Ni ratio is shown. ► Morphology, structure, electrochemical properties and coating composition are strictly correlated. ► Ni–Co alloys with 40–65% Co are the best cathodic material for HER in alkaline media. ► Cubic structure and finer globular morphology give the best catalytic properties.
•Indium electrowinning using sulfate solution on different metal cathode.•Using Ni, SS, Ti, Cu and Al as cathodes.•Effectiveness of the metal cathode on indium electrowinning.•Relevance order of the ...cathodes has been determinated•Higher performances are presented by Ni and SS cathodes for indium electrowinning.
Electrowinning represents a promising methodology for recovery of strategical, scarce metals. In this study, an indium electrowinning process using a sulfate electrolyte on stainless steel, nickel, titanium, aluminum and copper (SS, Ni, Ti, Al and Cu) cathodes was investigated. Firstly, cyclic voltammetry carried out at 15 mV/s scanning rate and 25 °C temperature evaluated the suitability of electrolyte and the surface reactivity on different metal cathodes. Subsequently, indium was deposited using a current density of 25 A/m2 for 22 h at 40 °C and pH 2.3. After electrowinning process, analysis of specific energy consumption (SEC), current efficiency (CE) morphological (SEM/EDX), and crystallographic (XRD) tests on obtained deposits were performed. Cyclic voltammetry results revealed that the chemical reagents of solution stabilize the indium reduction reaction, while Ni cathode showed the highest current intensity for reduction reaction followed by SS, Ti, Cu, and Al. With a significant CE and SEC performance, Ni and SS cathodes reached around 93 % CE and 1.67 kW h/kg SEC, respectively. Referring to Ti cathode, other optimization tests should be performed to enhance obtained results. After deposition process, different surface morphologies and different crystallinity degree can be observed for each deposit, being common the presence of surface defects. The findings of this investigation allowed to determine the most suitable cathode for indium electrowinning from sulfate electrolyte.
Solution template wetting is a common technique used to fabricate elongated polymer nanostructures; however, the parameters controlling the resulting morphology remain unclear. The purpose of this ...investigation was to elucidate the effects of process variables on the types of nanostructures obtained and to understand the physical mechanisms associated with structure development. 1 wt% polystyrene-THF solutions were infiltrated into commercial and homemade anodized aluminum oxide (AAO) templates. The wetting interaction between the AAO template and the polymer solution was examined through contact angle measurements. In general, for moderate dipping times (<18 h), the morphology of the nanopolymer was rod-like at low molecular weights, while tubes were observed at high molecular weight, even at this low concentration. Nanorods were obtained for all molecular weights for extended dipping times. The data suggest that phase separated layers may grow sequentially from the pore walls and yield nanotubes if the growth is interrupted or produce nanorods for unhindered deposition over long periods.
Drops of a suspension of individual single‐walled carbon nanotubes in F68 Pluronic surfactant dry on glass substrates to form a “crust” at the free surface. The crust is extremely thin (∼ 100 nm) and ...consists of an entangled mesh of nanotubes and Pluronic. The convective flow associated with the drying preferentially assembles the nanotube‐Pluronic micelles into a hexagonal arrangement, as revealed by birefringent patterns (see Figure and Cover).
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