Electrodeposition of actives species on carbonaceous materials for energy applications

The thesis work focuses on the electrosynthesis of active species on carbonaceous materials, their characterization and energy applications. Two protocols of electrochemical synthesis that lead to two forms of hexacyanoferrate copper (CuHCF) with different composition and structure, were applied. The procedure used is a “two–step” method that involves the deposition of metallic copper and the subsequent anodization in the presence of ferricyanide ion, using as support graphite sheet, carbon cloth and carbon toray paper. Another protocol was that of electrosynthesis of double layer hydroxide (LDH) containing cobalt as bivalent cation and aluminium or iron as trivalent metal, using as support graphite sheet, carbon cloth, carbon toray paper and nickel foam. After studying the correlation between the electrodeposition time and the masses obtained, the specific capacities of the deposited materials were calculated.The last used protocol was the electrochemical synthesis of nickel hexacyanoferrate on nickel foam. All the film obtained were electrochemically characterized by cyclic voltammetry. SEM – EDX and XRD analyses were performed on some samples in order to obtain morphological and chemical informations. Some tests were conducted using the supports or some of the electrodeposited samples as cathodes in lithium–air batteries, to understand their potential as sources of energy. After performing oxygen and argon cyclic voltammetries, controlling in what way the potential change at different current density and carrying out full discharge at constant current density, it was found that the carbon tissue was the one that produced the best results. It was decided to study in deep the behaviour of this support when active species are electrodeposited above it. As a parallel work, attempts were made to obtain porous carbon from hair, with the intention of using it as a support, in a slurry for example, for testing electrodepositions of active species mentioned above

Photopolymerization of ionic liquids in flexible microporous aramids for ion conductive solid polyelectrolytes

This work presents the preparation of novel solid polymer electrolytes based on flexible microporous aramids filled with photopolymerized ionic liquids and lithium salt. The materials combined a high ionic conductivity with the mechanical and thermal characteristics of the aramids, including also good flexibility and handleability. First, a simple casting process was followed to obtain microporous aramids with an interconnected channel morphology. In a second step, this channel structure was filled with a solution of non-commercial photopolymerizable ionic liquid, commercial ionic liquids and the lithium salt, followed by UV irradiation to obtain the conducting aramids. Ionic conductivity of the materials was studied at 25 °C, and also in the temperature range between −50 to 90 °C, together with SEM analyses of the filled porous structure and thermal properties, to fully characterize the photopolymerization process of the ionic liquids inside the porous structure. The materials showed high ionic conductivity values together with excellent thermal and mechanical properties, indicating their viability as flexible and thermally stable solid electrolytes.FEDER (Fondo Europeo de Desarrollo Regional) and both the Spanish Ministerio de Economía, Industria y Competitividad (MAT2017-84501-R and MAT2017-88923-P), the Consejería de Educacion-Junta ´ de Castilla y Leon ´ (BU306P18) and the Spanish Ministerio de Ciencia e Innovacion ´ (PID2019-108583RJ-I00/AEI/10.13039/501100011033)

Thin layer films of copper hexacyanoferrate: Structure identification and analytical applications

Thin films of copper hexacyanoferrate (CuHCF) have been reproducibly electrodeposited on conductive substrates according to two different potentiostatic methods, here denoted as A and B. For both methods two consecutive steps are involved, the first being the electrodeposition of a thin Cu layer, the second its partial dissolution and formation of CuHCF in presence of hexacyanoferrate anion, giving as result a two layers film (CuHCF on Cu metal). The main difference, instead, consists in the applied potential values and their application times, featuring Method A lower potentials but longer processing times. Structural insights have been achieved by means of X-ray Diffraction (XRD) and X-ray Absorption Fine Structure (XAFS) measurements, from which we can deduce the presence of Prussian blue (PB) impurities in Method A, while Method B leads to a pure CuHCF phase. Two analytical applications have been considered, ion exchange and H2O2 sensing. Ion exchange has been first assayed and, although CuHCF-A shows a higher stability towards multivalent cations, CuHCF-B is suitable for small hydrated ions. PB impurities in CuHCF-A boost its sensing towards H2O2, making it more adapted to this employment