• Energy Research

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Increasing energy autonomy and lowering dependence on lithium-based batteries are more and more appealing to meet our current and future needs of energy-demanding applications such as data acquisition, storage, and communication. In this respect, energy harvesting solutions from ambient sources represent a relevant solution by unravelling these challenges and giving access to an unlimited source of portable/renewable energy. Despite more than five decades of intensive study, most of these energy harvesting solutions are exclusively designed from ferroelectric ceramics such as Pb(Zr,Ti)O3 and/or ferroelectric polymers such as polyvinylidene fluoride and its related copolymers, but the large implementation of these piezoelectric materials into these technologies is environmentally problematic, related with elevated toxicity and poor recyclability. In this work, we reveal that fully biobased non-isocyanate polyurethane-based materials could afford a sustainable platform to produce piezoelectric materials of high interest. Interestingly, these non-isocyanate polyurethanes (NIPUs) with ferroelectric properties could be successfully synthesized using a solvent-free reactive extrusion process on the basis of an aminolysis reaction between resorcinol bis-carbonate and different diamine extension agents. Structure-property relationships were established, indicating that the ferroelectric behavior of these NIPUs depends on the nanophase separation inside these materials. These promising results indicate a significant potential for fulfilling the requirements of basic connected sensors equipped with low-power communication technologies.

[ES] En este trabajo, se estudia la influencia de la forma del electrodo elemental y la microestructura del contacto electrodo-electrolito, del electrodo de gas a difusión interna en celdas de combustible de óxido sólido (SOFC). Se determina la influencia de la microestructura del contacto electrodo electrolito sobre la resistencia efectiva del electrolito, la influencia de la forma del contacto de un grano elemental de un electrodo poroso suponiendo que sea aproximadamente una semiesfera sobre la reacción del electrodo y finalmente la influencia de la microestructura del contacto electrodo - electrolito en la respuesta a un control difusivo puro del electrodo. De los resultados obtenidos se pueden extraer conclusiones sobre la influencia de la microestructura del contacto y forma del electrodo en la reacción de oxígeno en este tipo de electrodos de gas. [EN] In this work we have studied the elemental electrode shape and electrode - electrolyte contact microstructure influence of Internal diffusion (ID) gas electrode in solid oxide fuel cells (SOFC). First the influence over the electrolyte effective resistance is studied. Then the influence of the shape of the elemental contact grain of ID electrode is also studied. Finally the influence of the electrode - electrolyte contact microstructure in the electrode response for a pure diffuse control is modelled. From the obtained results, conclusions on the contact microstructure and electrode shape influence over the oxygen reaction of this kind of gas electrodes are commented. R. Jiménez quiere agradecer al Consejo Superior de Investigaciones Científicas la beca postdoctoral que hizo posible la realización de este trabajo. Peer reviewed

Simple and cost-effective procedures for the direct integration of ferroelectric perovskite oxides into Ni structures are necessary to realize related multifunctional metallic microelectromechanical systems, such as dual-source energy harvesters. This is especially difficult in the case of lead-containing morphotropic phase boundary materials for high piezoelectric response because the two components are thermodynamically incompatible and the formation of NiOx or perovskite oxide reduction takes place depending on the processing conditions. We show here that low-temperature solution processing is an effective means to kinetically limit nickel oxidation, capable of providing BiFeO3–PbTiO3 films on Ni plates at only 500 °C. Bulk-like ferroelectric properties and a distinctive magnetoelectric response were attained. This perovskite system, not explored before on Ni, has a much larger switchable polarization than the widely studied Pb(Zr,Ti)O3, and it is shown here to present an excellent downscaling behavior of ferroelectric properties until the verge of the nanoscale.

Three-dimensional microchannelled nanocomposite electrodes fabricated by ice-segregation induced self-assembly of chitosan-dispersed multiwall carbon nanotubes are shown to provide a scaffold for growth of electroactive bacteria for use as acetate-oxidizing bioanodes in bioelectrochemical systems. The hierarchical structure provides a conductive surface area available for G. sulfurreducens colonization, with a flow through configuration along the electrode providing a substrate for bacterial colonization and bio-electrochemical processes. This configuration, whilst resulting in sub-monolayer biofilm coverage over the three-dimensional surface, is capable of providing acetate oxidation current densities of up to 24.5 A m−2, equating to a volumetric current density of 19 kA m−3, in the flow-through configuration. Such bioanodes, when operated in non-optimized flow-through microbial fuel cell configuration, provide a maximum power density of 2.87 W m−2, which is equivalent to 2.0 kW m−3 volumetric power density.