Platinum Electrodeposition in an Ionic Liquid Analogue. Solvent Stability Monitoring

The use of ionic liquid analogues as solvents has increased in order to substitute the aqueous solvents in some applications in which the side reactions are undesirable. However these solvents prepared from the mixture in the eutectic proportion of species establishing hydrogen bonds are susceptible of electrochemical reactions. The study of platinum deposition on vitreous carbon in an ionic liquid analogue (2 urea: choli ne chloride) is presented; the electrochemical study has permitted to interpret the sequence of the metal deposition process and simultaneously to analyze the behavior of the ionic liquid analogue along the process. Reduction reactions of the solvent relat ed both to the electronation of choline and hydrogen formation have been detected. Different substrata have been used in order to test the possibility and the extent of these reactions depending on the nature of material. The results indicate that the feas ible electrochemical window of the substrate/solvent is highly dependent of the kind of substrate; the negative limit is tied by the massive hydrogen reaction, reaction enhanced by the electrocatalytic character of the substrate

Co-Ni-carbon flexible composite fibres for directional magnetic actuation

Flexible microcomponents are being widely employed in the microelectronic industry; however; they suffer from a lack of complex movement. To address this problem, we have developed flexible, electrically conductive, magnetic composite fibres showing complex motion in three dimensions with the capacity to be selectively actuated. Flexible carbonbased fibres were prepared by wet-spinning and were subsequently modified by electrodepositing Co-Ni. The high aspect ratio of the fibre (40 μm diameter, 3.5 cm length) causes a directional dependence in the magnetostatic energy, which will allow for anisotropic actuation of the composite. Thus, the application of magnetic fields allows for a precise control of the movement with high reproducibility and accuracy

Proyecto de innovación docente: “eCONclase (escapando de 1984)”

En este Trabajo Fin de Máster se desarrolla y analiza la propuesta educativa denominada “eCONclase (escapando de 1984)”, que plantea el diseño y la construcción de un medio de comunicación digital, además de la realización de una colaboración en papel con la revista mensual de la localidad, en la materia de Economía de 4º de la ESO. El presente trabajo tiene la finalidad de realizar una puesta en valor de un proyecto colaborativo fundamentado en las TIC como elemento central de una propuesta didáctica innovadora donde se potencie la motivación del alumnado así como un aprendizaje más significativo. Para facilitar el hilo argumental de la asignatura se utilizará como recurso la novela distópica de George Orwell, 1984.<br /

Copper electrodeposition in a deep eutectic solvent. First stages analysis considering Cu(I) stabilization in chloride media

The aim of the present work is to study copper electrocrystallization in a Deep Eutectic Solvent (DES) (eutectic mixture of choline chloride and urea 1:2) as electrolyte, paying special attention to the influence of the liquid on the nucleation mechanism. Deposition process was studied from both Cu(II) and Cu(I) solutions. As the DES solvent is chloride rich, a parallel analysis was made in aqueous solution containing an excess of chloride to compare medium influence on nucleation mechanism. While copper (I) can be directly electrodeposited from chloride excess solutions, copper (II) electrodeposition takes place via a separate step in which Cu(II) is firstly reduced to Cu(I). A methodology is proposed for studying mechanistic aspects of the early stages of copper electrodeposition from the Cu(II) chloride solutions. For all solutions, cyclic voltammetry was used to establish the potential range at which copper electrodeposition occurred, while potentiostatic technique was used to study the nucleation mechanism. In all media, deposition follows a nucleation and three-dimensional growth controlled by diffusion. The diffusion coefficient of Cu(I) species present in the solution has been calculated from potentiostatic curves by logarithmic linear regression of j vs t−1/2 at long deposition times, whereas the same parameter for copper (II) was calculated from cyclic voltammetry, taking advantage from the process quasi -reversibility. The viability of the nucleation mechanism by Scharifker-Hills model was demonstrated by the analysis of the rising part of the j-t transients independently of the selected solution

First stages of silver electrodeposition in a Deep Eutectic Solvent. Comparative behaviour in aqueous medium

The aim of the present work was to study the viability of a deep eutectic solvent (DES) solvent (consisting in a eutectic mixture of 1 choline chloride: 2 urea) as electrolyte for the electrodeposition of silver (I), paying special attention to the influence of the liquid on the mechanism of nucleation process. As this DES solvent is rich in chloride anion, which can act as complexing agent of the silver cation, parallel analysis was made, as reference, in aqueous media, both in free-chloride solution and in excess of chloride. These studies were made to analyze the role of chloride anion on the first stages of silver electrodeposition, but also to compare as nucleation mechanism changes depending on the medium, especially when DES solvent was used. For all solutions, cyclic voltammetry was useful to establish the potential range at which silver electrodeposition occurred, while potentiostatic technique was used to study the mechanism of the process. In all media, the deposition follows a nucleation and three dimensional growth governed by diffusion. The viability of the nucleation mechanism by Scharifker-Hills model was demonstrated. The analysis of the rising parts of the j-t transients confirms the obtained results by the model. Diffusion coefficients of silver species present in the solution were calculated from linear regression of j vs t−1/2 at long deposition times

Electrochemical growth of CoNi and Pt-CoNi soft magnetic composites on an alkanethiol monolayer-modified ITO substrate

CoNi and Pt-CoNi magnetic layers on indium-tin oxide (ITO) substrates modified by an alkanethiol self-assembled monolayer (SAM) have been electrochemically obtained as an initial stage to prepare semiconducting layer-SAM-magnetic layer hybrid structures. The best conditions to obtain the maximum compactness of adsorbed layers of dodecanethiol (C12-SH) on ITO substrate have been studied using contact angle, AFM, XPS and electrochemical tests. The electrochemical characterization (electrochemical probe or voltammetric response in blank solutions) is fundamental to ensure the maximum blocking of the substrate. Although the electrodeposition process on the SAM-modified ITO substrate is very slow if the blocking of the surface is significant, non-cracked metallic layers of CoNi, with or without a previously electrodeposited seed-layer of platinum, have been obtained by optimizing the deposition potentials. Initial nucleation is expected to take place at the pinhole defects of the C12-SH SAM, followed by a mushroom-like growth regime through the SAM interface that allows the formation of a continuous metallic layer electrically connected to the ITO surface. Due to the potential of the methodology, the preparation of patterned metallic deposits on ITO substrate using SAMs with different coverage as templates is feasible

Influence of the composition and crystalline phase of electrodeposited CoNi films in the preparation of CoNi oxidized surfaces as electrodes for urea electro-oxidation

Oxidized species of CoNi have been obtained by means of electrodeposition of CoNi films and posterior electro-oxidation, to obtain electrodes able to be catalysts of oxidative reactions in alkaline medium. The products of electro-oxidation formed, which depend on the composition and the crystal phase of CoNi deposits, have been identified; for this, Co-fcc, Co-hcp, Co7Ni3-fcc, Co7Ni3-hcp, Co5Ni5-fcc and Ni-fcc films have been electrodeposited and oxidized. The influence of the crystalline phase of the films in the nature of the superficial oxides formed has been demonstrated: the electrodes prepared from CoNi-fcc films contained _-CoxNi(1−x)(OH)2, while those prepared from Co7Ni3-hcp films contained Co2NiO4and _- CoxNi(1−x)(OH)2. The catalytic behaviour of the electro-oxidized electrodes for urea electrooxidation was evaluated. Separate tests were performed to differentiate the influence of the composition and the crystalline structure of the initial films and, therefore, of the different oxidized species formed. The electrodes prepared by electro-oxidation of the Co7Ni3-hcp films show better electro-catalytic performance for urea's oxidation than those obtained by oxidation of the Co7Ni3-fcc, because they induce higher intensity, lower onset potential and lesser simultaneous oxygen evolution, becoming a good anode for ureelectro-oxidation in urea electrolysis for hydrogen production or waste water treatmen

Facile electrochemical synthesis, using microemulsions with ionic liquid, of highly mesoporous CoPt nanorods with enhanced electrocatalytic performance for clean energy

We have established a facile and generalizable electrochemical synthesis of metallic mesoporous nanorods in the nanochannels of commercial polycarbonate membranes using microemulsions containing ionic liquids. Herein, we report the preparation of magnetic CoPt nanorods with various meso or nanopores distributions, depending on the microemulsion type (ionic liquid in-water (IL/W), bicontinuous (β) or water-in-ionic liquid (W/IL)). The synthesized porous nanorods show a much enhanced electrocatalytic activity for methanol oxidation in comparison with compact Pt nanorods (up to 12 times) or Pt/C electrocatalyst (Pt nanoparticles or commercial black platinum). Therefore, the synthesized CoPt mesoporous nanorods could be excellent catalysts in direct methanol fuel cells (DMFC's), as they have high surface areas, large pore volumes and high corrosion stability, and they exhibit promising catalytic properties

Synthesis and stability of Pt3Co and Pt0.7≤X≤1Co films voltammetrically activated in acidic medium for methanol fuel cell application

Pt-Co thin films have been prepared by means of electrodeposition method, due to the interest of this alloy as catalyst in acid fuel cells. As the stability of the catalyst is fundamental to consider its applicability, the behavior of the films as a function of the composition during voltammetry activation in acidic medium has been studied. The Pt3Co films show high stability, maintaining their morphology, X-ray diffraction profile, composition and high surface area, and show good catalytic behaviour for methanol electro-oxidation in acidic medium. However, the Pt0.7≤x≤1Co films present low stability and evolve during the test to flatter films of lower effective area and Pt3Co stoichiometry, by losing cobalt. Only Pt-Co electrodeposited films of defined compositions show the enough stability and properties to be used as good materials for electro-oxidation processes in acidic media

Alginate electrodeposition onto three-dimensional porous Co-Ni films as drug delivery platform

Three-dimensional porous Co-Ni films/alginate hybrid materials have been successfully prepared by electrodeposition to be used as a steerable magnetic device for drug delivery. Firstly, 3D porous Co-Ni films were prepared as substrates for the subsequent electrodeposition of the alginate biopolymer. Cyclic voltammetry, galvanostatic and potentiostatic studies were performed to establish the best conditions to obtain porous Co-Ni films. The electrochemical experiments were carried out in an electrolyte containing the metal salts and ammonium chloride at low pHs. In a second stage, the electrochemical deposition of alginate as a biocompatible polymer drug delivery carrier was performed. The characteristics of the alginate matrix were investigated in terms of electrochemical properties, morphology and drug release. The hybrid material obtained showed soft-magnetic behavior and drug release indicating its suitability to be used as a steerable magnetic drug delivery device