Acanthaceae Bentham G. & J.D. Hooker

Se da a conocer los géneros y especies de Acanthaceae cultivadas en el -ámbito urbano de Mendoza-San Juan-La Rioja.Fil: Martinez Carretero, Eduardo Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico - CONICET - Mendoza. Instituto Argentino de Investigaciones de Zonas Aridas; Argentina;Fil: Ganci, Carmelo.Fil: Elmida, Carina

Nanostructured electrochemical devices for sensing, energy conversion and storage

Nanostructured materials are attracting growing interest for improving performance of devices and systems of large technological interest. In this work, the principal results about the use of nanostructured materials in the field of electrochemical energy storage, electrochemical water splitting, and electrochemical sensing are presented. Nanostructures were fabricated with two different techniques. One of these was the electrodeposition of the desired material inside the channels of a porous support acting as template. The other one was based on displacement reaction induced by galvanic contact between metals with different electrochemical nobility. In the present work, a commercial polycarbonate membrane was used as template. In the field of the electrochemical energy storage, the attention was focused on lead-acid battery, and it has been found that nanostructured morphology enhances the active mass utilization up to about 80%, with consequent increase of specific energy and cycling rates to unattainable values for the commercial battery. Nanostructured Ni-IrO2 composite electrodes showed valuable catalytic activity for water oxidation. By comparison with other Ni-based electrocatalyst, this electrode appears as the most promising anode for electrochemical water splitting in alkaline cells. Also in the field of sensing, the nanostructured materials fabricated by displacement reaction showed performance of high interest. Some new results about the use of copper nanowires for H2O22 sensing will be showed, evidencing better performance in comparison with copper thin film. In this work, we will show that nanostructured electrodes are very promising candidate to form different electrochemical setups that operate more efficiently comparing to device with flat electrode materials

Flexible electrode based on gold nanoparticles and reduced graphene oxide for uric acid detection using linear sweep voltammetry

In this work, an electrochemical sensor for uric acid determination is shown with a preliminary study for its validation in real samples (milk and urine). Uric acid can be electrochemically oxidized in aqueous solutions and thus it is possible to obtain electrochemical sensors for this chemical by means of this electrooxidation reaction. Indium tin oxide coated on flexible polyethylene terephthalate substrate, modified with reduced graphene oxide and gold nanoparticles by co-electrodeposition, was used. Electrodeposition was performed at -0.8V vs SCE for 200 s. All samples were characterized by electron scan microscopy and electron diffraction spectroscopy. A careful investigation on the effect of pH was performed to understand its influence on uric acid oxidation. The detection of uric acid was using the linear sweep voltammetry. Results show that the peak current increases linearly with uric acid concentration from 10 to 1000 μM with a limit of detection of about 7.1 μM. The sensor shows high selectivity towards different interferents that can be found in the milk and urine matrix, such as chloride, calcium, sodium and ammonium ions. To prove the applicability of the proposed sensor, uric acid was quantified in real milk and urine samples with excellent results comparable to those of conventional techniques

Nanostructured electrodes for hydrogen production in alkaline electrolyzer

Ever-widespread employment of renewable energy sources, such as wind and sun, request the simultaneous use of effective energy storage systems owing to the intermittent and unpredictable energy generation by these sources. The most reliable storage systems currently under investigation are batteries and electrochemical cells for hydrogen production from water splitting. Both systems store chemical energy which can be converted on demand. The low power density is the weakness of the batteries while the high production cost limits currently the wide use of hydrogen from electrochemical water splitting. In this work, attention was focused on the use of nanostructured Ni as a cathode for electrochemical production of hydrogen from alkaline solution. The work is aimed at analysing the energy dissipation at 0.5 Acm\ue2\u88\u922, which is a value of applicative interest, for detecting one of the cause determining the high production cost. The development of electrochemical cells employing alkaline solution is currently the most promising approach in comparison with electrolysers using acidic solution which are expensive, because require precious metals as electrodes and high cost cation-selective membrane for efficiently conducting water splitting. Nanostructured Ni electrodes were fabricated through a cheap and easily scalable process, based on the Ni electrodeposition inside the pores of a commercial polycarbonate membrane acting as a template. On the contrary, a galvanic connection driving a spontaneous displacement reaction was employed for synthesising Pd nanostructured electrode which was tested for comparison purposes. Once the membrane is dissolved in an organic solution, the electrodes were initially characterized by SEM, EDS and XRD analysis. Then, electrochemical tests were performed to evaluate electrocatalytic properties of the electrodes. The tests were conducted through either cyclic or linear sweep voltammetry in 30% w/w KOH aqueous solution. Then, the nanostructured electrodes were tested under constant current density of 0.5 Acm\ue2\u88\u922. In comparison with nanostructured Pd, Ni electrodes with the same morphology and in otherwise identical conditions show a better response in terms of electrocatalytic activity. In addition, these electrodes showed satisfying stability over time through tests longer than 60 h. The analysis of energy dissipation revealed that the prevalent contribution was due to the ohmic drop)which can be reduced through a properly cell design) based on the accurate control of the parameters determining ohmic drop inside the cell

Nanostructured Ni-Co Alloy Electrodes Fabrication and Characterization for both Hydrogen and Oxygen Evolution Reaction in Alkaline Electrolyzer

Sun and wind as power sources are becoming more and more relevant owing to the progressive abandoning of the fossil fuels [1,2]. Additionally, worldwide public authorities are encouraging the use of renewable energies by promoting laws and guidelines [3,4]. In this scenario, a fundamental role can play hydrogen that besides being a valuable energy carrier, it can also act as a storage medium to balance the discontinuity affecting the renewable energy sources production [5]. As a consequence, cheap and abundant availability of hydrogen is crucial. Electrochemical water splitting is likely one of the most valuable technique to produce hydrogen because the process is environmentally friendly being electron a reagent, which, unfortunately, enhances the cost. The minimum energy requested is 39.67Wh per g of hydrogen. This value increases more or less owing to the electrodes overvoltage that depends on the current density passing through the electrolyzer. One approach to improve the performance of a water splitting electrochemical cell is based on the development of nanostructured electrodes distinguishing for low cost and high electrocatalytic activity. By template electrosynthesis, we have fabricated Ni nanowires featured by very high surface area. In previous works, we have shown that water-alkaline electrolyzer with Ni nanowires electrodes covered by nanoparticles of IrO2 as an anode and Pd as a cathode have good and stable performance also at room temperature [6-7]. In this work, the attention has been focused on the fabrication of nickel-cobalt electrodes. In particular, starting from aqueous solutions containing both elements at different concentrations, alloyed electrodes with different compositions were fabricated through electrodeposition into a template. The chemical and morphological features of these nanostructured electrodes will be presented and discussed. Furthermore, electrochemical and electrocatalytic tests aimed to establishing the best alloy composition were carried out for both hydrogen and oxygen evolution reaction. Then, long term test conducted at a constant current density in aqueous solution of potassium hydroxide (30% w/w) will be also reported

Ni and Ni-Pd nanostructures electrodes for water-alkaline electrolyses

Hydrogen production by water electrolysis (WE) is a very promising technology because it is a pollution free-process specially if renewable energy are employed. Up to day, the cost of hydrogen production by WE is higher than other available technologies, making WE not competitive. Many efforts have been made to improve WE performance, through the use of electrodes made of transition metal alloys (Pt2Mo, TiPt) as a cathode or pyrochlore type oxide (Tl2RuxIr2-xO7) as an anode [1]. In the field of water-alkaline electrolyzer, the development of cheap nanoporous nickel electrodes with high electrocatalytic features is one of the potential approaches to increase the WE performance [2]., A facile method for obtaining nanostructured electrodes is template electrosynthesis. Through this method, we have fabricated electrodes formed of Ni nanowires that have a very high surface area. In a preliminary work, we have shown that alkaline electrolyzer assembled with IrO2 nanoparticles covering Ni nanowires, acting as an anode, and a Ni sheet, acting as cathode, shows very good and stable performance also at room temperature [3]. In this work, the attention was focused on the fabrication of electrodes for hydrogen evolution reaction (HER). In particular, through metal displacement deposition, we have deposited nanoparticles of Pd on Ni nanowires electrodes with the aim to enhance the electrocatalytic performance of Ni nanowires shown in Figure 1. The results on the growth and characterization of nanostructured composite electrodes will be presented and discussed. Preliminary test on the electrolyzer performances, carried out at constant current in 30% w/w aqueous solution of potassium hydroxide, will be also reported

Fabrication of Nanostructured Ni and Ni-IrO2 electrodes for wateralkaline electrolyzer

In the field of water-alkaline electrolyzer, the develop of nanoporous nickel electrodes with low cost and high electrocatalysis efficiency is one of the potential approaches to increase their performance [1]. To obtain nanostructured electrodes, a facile approach is that of template electrosynthesis. With this method we have obtained electrodes made of nanowires of Ni that have a very high surface area. These electrode were obtained by a two-step procedure allowing to obtain an ordered array of Ni nanowires that completely covering the surface of current collector made of the same material. Besides, by amperostatic deposition we have covered these electrode with nanoparticles of IrO2 electrocatalyst. In this work, the results on the growth and characterization of these nanostructured electrode will be presented and discussed. Ni NWs were obtained by pulsed potential deposition into polycarbonate membranes [2]. IrO2 electrocatalyst was deposited on Ni NWs by different electrochemical techniques, like cyclic voltammetry and potentiostatic deposition [3]. For comparison, IrO2 electrocatalyst was also deposited on a Ni flat substrate. All electrodes were characterized by SEM, EDS, and XRD analyses. Moreover, the preliminary test on the electrochemical performances, carried out at constant current in 1M aqueous solution of potassium hydroxide, will be also reported. [1] D. Pletcher, X. Li Intern. J. Hydrogen energy 36 (2011) 15089. [2] R. Inguanta, S. Piazza, C. Sunseri Electrochem. Acta 53 (2008) 5766. [3] E. Ahlberg, P. Steegstra Electrochem. Acta 68 (2012) 206

Fabrication and characterization of nanostructured Ni and Pd electrodes for hydrogen evolution reaction (HER) in water-alkaline electrolyzer

In the field of water-alkaline electrolyzer, the development of nanoporous low cost nickel electrodes is one of the potential approaches to increase electrocatalytic activity. Template electrodeposition is a facile and cheap technique for obtaining Ni nanowires (NWs) with high surface area. These nanostructures were fabricated by a two-step procedure. In the first step, a Ni compact layer was deposited on one side of the template where a gold film was previously sputtered, while, in the second-step, an ordered array of Ni-NWs was obtained by electrodeposition inside the template channels. The NWs were firmly connected to the underlying Ni layer, acting as a current collector. In order to enhance the catalytic activity, Pd nanoparticles were deposited onto the NW surface by metal displacement. All electrodes were characterized by Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS). The comparison between the two types of electrodes revealed that the composite electrode (Ni+Pd) shows better electro-catalytic features, which quickly decay under operation, so that after 5 min. of polarization at a constant current in 30% w/w aqueous solution of potassium hydroxide, the other electrode performs better

Dispositivo elettrolizzatore migliorato

Un dispositivo di elettrolizzatore migliorato per la produzione elettrolitica di idrogeno allo stato gassos