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En el presente trabajo se analizó el efecto de la eficiencia de inhibición del acero 1045, modificado superficialmente con electrodepósitos de zinc sintetizados en un disolvente eutéctico profundo (DES), constituido por cloruro de colina con urea (conocido como reline) y cloruro de zinc al aplicar diferentes potenciales. La evaluación electroquímica fue realizada por curvas de polarización potenciodinámicas para obtener la densidad de corrosión y la eficiencia de inhibición de los diferentes electrodepósitos de zinc. Las superficies del acero 1045 fueron caracterizadas mediante microscopía óptica para evaluar las modificaciones debidas al proceso de corrosión en el medio ácido.

En este trabajo se presenta un estudio fundamental de las primeras etapas involucradas en el proceso de formación y crecimiento de núcleos metálicos electrodepositados sobre substratos de diferente naturaleza, a partir de disoluciones acuosas de sus iones. Dicho estudio se basa principalmente en el análisis de transitorios potenciostáticos de corriente, obtenidos en cada sistema, a través de modelos teóricos previamente publicados en la literatura; y otros desarrollados, en el transcurso de este trabajo de investigación. Se pone especial atención a la influencia de las propiedades fisicoquíxnicas de la disolucicm (p.e. concentración de la especie electroactiva, esfera de coordinación del ion metálico, temperatura del baño electolitico) sobre los mecanismos y la cinética del electrodepósito (determinación de velocidades de nucleación, densidad de sitios activos de \ nucleación sobre la superficie de los substratos, tamaño del núcleo crítico). Para interpretar las formas complejas de algunos transitorios obtenidos a lo largo de esta tesis, no d.escritas por ninguno de los formalismos teóricos hasta ahora publicados, se plantean modelos de mecanismos de depósito que involucran, tanto la presencia simultánea de diferentes modos de nucleación, como de la evolución de reacciones redox (p. e. evolución de hidrógeno) sobre la superficie de los núcleos recién formados. Los mecanismos propuestos en este trabajo, describen con detalles (ecuaciones matemáticas) dichos procesos complejos, ofreciendo en todos los casos un andisis cuantitativo del fenómeno.

Low temperature fuel cell technology is set to occupy a central role in powering society in the near future. Several challenges emerge in the preparation of electrocatalysts to improve the operation, use and commercialization of fuel cells. Bi-metallic nanostructures are potential materials to use as electrocatalysts in this application. This research studies the electrocatalytic activity of palladium-copper nanostructures supported on graphene oxide as electrocatalysts for the formic acid oxidation reaction (FAOR). The Pd-Cu nanostructures were synthesized through the impregnation method using tetrachloropalladium acid and sodium borohydride. The Pd and Cu precursors were mixed in appropriate quantities to obtain Pd:Cu molar 1:1 ratios. The Pd-Cu nanostructures were characterized via X-rays diffraction, XRD, transmission, TEM, and scanning electron, SEM, microscopies. The electrocatalytic activity of the Pd-Cu nanostructures was evaluated for the FAOR. Figure 1 shows the cyclic voltammetries used to determine the electroactive area using the CO adsorption/desorption. The FAOR is shown in Figure 1B, where Pd-Cu is the electrocatalyst displaying the largest anodic current density as compared with Pd and commercial Pd. Figure 1

This research work studied Cu electrodeposition over a glassy carbon electrode (GC) using deep eutectic solventes (DESs) instead of conventional aqueous media to subsequently assess the electrodeposit catalytic properties during nitrates reduction. These are nitrogen’s most reduced form, typically present in residual waters from chemical industries, from human consumption and from agriculture, which represent a significant contamination problem; they are not at all easy to eliminate through conventional methods used in water treatment plants, because they can reach potable water sources provoking in humans the incidence of severe illnesses, like cancer among others. It has been shown, that catalysts based in Pd, Pt and Cu metal phases reduce the nitrate ions, where the Cu ones have been studied because of their attractive catalytic properties. There are various forms of synthesizing the Cu catalysts, where electrodeposition leads to better control of Cu nucleation and growth. Cu electrocristalization was carried out from DES to compare the influence of the medium over the nucleation and growth mechanism. The eutectic mixtures used were prepared from choline chloride as the ionic species while the hydrogen bond donnors were urea and ethylene glycol. Both the DES were prepared in a 1:2 molar ratio, taking particular care to establish the influence of the resulting liquid at the early stages of electrodeposition, which was studied from Cu (II) solutions. It was shown that its electrodeposition takes place through a separte stage during which Cu (II) reduces first to Cu (I). All media studied led to demonstrate that electrodeposition follows a nucleation and 3D diffusion controlled growth. The Cu (II) diffusion coefficient, the A (nucleation frequence) and N0 (number density of active sites) parameters were estimated from potentiostatic plots using the Heerman and Tarallo model. The nitrates reduction at different concentrations was studied via differential pulse voltammetry to determine analytical parameters, like sensibility, detection and quantification limits. The Cu-modified glassy carbon electrodes and a Cu bar served to reduce the nitrates, immersed in 100 mM NaCl supporting electrolyte at pH=1.4 set with HClO4 analytical grade, adding different KNO3 concentraciones. It was shown that in acid medium the nitrates ion can be quantified reliably. Figure 1

In the last decades, fuel cells have been considered as an alternative power source for electric portable devices. Direct formic acid fuel cells (DFAFC) have attracted particular interest, since formic acid is safe, environmentally-friendly and non toxic. Also, it exhibits high-energy density and fast oxidation kinetics compared with other fuels, such as methanol and ethanol [1]. Palladium electrocatalysts supported on different carbon materials have been widely used for the formic acid oxidation reaction (FAOR). However, further research is still necessary as Pd deactivates during the FAOR. In order to overcome this limitation, Pd-Metal alloys have been proposed [3-5]. Pd, and PdFe nanoparticles supported on the carbon nanofibers with and without functionalization (NFC and NFCox) have been used for the FAOR in acid media. Electrocatalysts were synthesized by the borohydride reduction method with a metal loading of 20 wt.%. The morphology, composition and structural properties of the electrocatalysts were studied by transmission electron microscopy (TEM), scanning electron microscopy-energy dispersive X-ray (SEM-EDX) and X-ray diffraction (XRD). The ROAF was evaluated in acid media in a conventional three-electrode cell by means of cyclic voltammetry (VC) and chronoamperometry (CA). The electrochemical behavior of Pd-based electrocatalysts for the FAOR showed that the functionalization of carbon nanofibers (NFCox) increased the electrocatalytic activity of Pd and PdFe electrocatalysts compared with the same electrocatalysts supported on NFC, as shown in Figure 1. X. Yu, P. Pickup, Journal of Power Sources,. 182(124-132) (2008) K. Jiang, H. Xuan, S. Zou, W. Bin, Phys. Chem. Chem. Phys., 16(20360-20376) (2014) H. Meng, F. Xie, J. Chen, P. Kang, Journal of Materials Chemistry., 21(11352-11358) (2011) D. Morales, J. Ledesma, L. Godinez, H. Rodríguez, L. Álvarez, L. Arriaga, Journal of Power Sources., 195(461-465) (2010) L. Zhang, L. Wan, Y. Ma, Y. Chen, Y. Zhou, Y. Tang, T. Lu, Applied Catalyst B: Environmental., 138-139(229-235) (2013). Figure 1