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Solid Oxide Fuel Cells (SOFCs) are nowadays one of the most promising devices for stationary clean energy production, due to their minimal Green House Gas (GHG) emissions, fuel flexibility (from hydrogen to hydrocarbons and biogas), high efficiency, and power density. They are essentially multilayer structures were a solid dense electrolyte is sandwiched between two porous electrodes. The mechanical resistance of the cell is given by the supporting element, most commonly the thick anode and the electrolyte is an yttria doped zirconia ionic conductor. The single cells are then connected through metallic plates that act as current collectors. Even if this technology is in the verge of commercialization, more work is needed to improve the lifespan and reliability of the single device. In this respect a major role is played by materials. Most of the work is at the moment devoted to reducing the temperature of operation (most commonly 800°C) using most performant materials (such as protonic conductors, ceria-based anionic conductors, etc.), reduce the amount of critical elements and improve the resistance of interconnectors and sealant. The article thoroughly revised the materials considered for the development of the single cell (electrolyte, cathode, and anode) and the cells stack (interconnector, sealant) in light of the more promising actual studied.

Tape casting is a widely used shaping technique to produce large-area, flat ceramic layers for SOFC applications. This cheap and easily scalable ceramic process generally makes use of pore forming agents in the slurry to produce elements with the desired porosity. In this work, the possibility to obtain porous La0.8Sr0.2MnO3-Ce0.8Gd0.2O2 (LSM-GDC) supporting cathode without the use of pore formers was evaluated. The reactive sintering approach was therefore considered to exploit the porosity induced by the precursor decomposition during a single thermal treatment of calcining-debonding-sintering. A stable tape casting slurry of lanthanum, strontium and manganite precursor salts and GDC powder was therefore used in order to obtain large-area, crack free green tapes where La0.8Sr0.2MnO3 phase was formed directly during the sintering step. This process allowed to obtain 10 x10 cm2 LSM-GDC tapes, 800 ?m thick, with values of porosity and mechanical strength suitable for fuel cells applications without pore former addition and in a single thermal step. To the author knowledge this is the first time that a large area supporting cathode has been produced by tape casting using the reactive sintering approach

Fuel Cell are electrochemical devices that convert the chemical energy of a fuel (generally hydrogen) and oxygen in electrical energy producing at the same time water and heat. These systems are interesting not only for the possibility of producing "clean" energy but also for the benefit linked to the high conversion efficiency. The Solid Oxide Fuel Cells (SOFC) in particular, are considered the most promising among the new systems of energy production especially for their intrinsic fuel flexibility (hydrocarbon, hydrogen, biogas, etc.). For these reasons, basic as well as technological studies focused on the improvement of the materials and production paths are of paramount importance to obtain SOFC competitive with the traditional energy production systems. Part of ISTEC research is devoted to the development of chemical synthesis able to produce tailored nano-oxides with characteristics suitable for SOFC applications. In particular soft-chemical synthesis routs were optimized to synthesize ceria and gadolinium-doped ceria nano-powders. Nano-structured powders exhibit in fact several size-dependant properties; among those, their high reactivity allows milder sintering conditions and as a consequence, better performances and lower production costs. Cerium oxide has been extensively used in a wide range of applications ranging from three way catalysts to gas sensors. When doped with gadolinum oxide, ceria becomes an alternative electrolyte for Intermediate Temperature Solid Oxide Fuel Cells (IT-SOFC). Nano-structured ceria has recently attracted extensive attention because of its properties which were found to be size, shape and orientation-dependent. Although several methods were proposed for the synthesis of ultrafine powders, most of them generally require a subsequent calcination step. This thermal treatment is known to promote the crystallisation of the amorphous phase; however it also induces aggregation, reducing the specific surface area of the powder. The aim of this work was to produce ultrafine, pure and Gd-doped CeO2 powders using standard chemical routes coupled with non-conventional heating processes. Nano-crystalline ceria and Ce1-xGdxO2- (GDC) particles were successfully produced under mild conditions with two different methods: i) applying infrared heating to a common sol-gel process (IR-SG); ii) assisting with microwaves a polyol precipitation method (MW-PP). The correlation of the synthesis parameters with the thermodynamic and kinetic factors involved, allowed the control of fundamental properties such as size distribution, purity and morphology. Nano-structured ceria of particle size in the micron range with complex morphology and high specific surface area was prepared by adjusting the MW-PP synthesis conditions (temperature, time and templating agents). These mesoporous aggregates were found to be active in the catalytic oxidation of toluene. Moreover the GDC obtained through the optimization of the IR-SG parameters exhibited values of ionic conductivity higher than the ones showed by commercial and conventional sol-gel produced powders of similar composition

The climate change, the decreasing of petroleum supplies and the abrupt increase of the energy demand due to the emerging countries and to an energy-hungry society, has driven the interest towards new energy and more efficient devices of energy production. Only a strong acceleration of alternative devices of energy production and an increase of renewables, can succeed in reducing pollution, improving the climate and at the same time assuring the energetic autonomy and competitiveness. In this scenario, electrochemical cells show several economic and environmental advantages compared to the conventional industrial processes. Fuel cells are an excellent alternative to the conventional systems of energy production in terms of CO2 emissions, low noise and flexibility of fuels and generated power. Solid oxide fuel cells (SOFC) in particular, are one of the most promising energy devices for their high efficiency, modularity, low emissions and the possibility to be directly fuelled with natural gas, GPL and alcohols. Lot of efforts are however necessary to develop commercially available generators and to increase their stability lowering at the same time their costs. These hurdles can be partially overcome lowering the operating temperature but also using more economic and easily scalable manufacturing techniques. These objectives can be reach deepened the knowledge on the relationships between SOFC materials and the main industrial production processes (tape casting and screen printing) necessary to obtain cell of dimensions close to the commercial ones with easily scalable processes. In this work the main issues related to tape casting and screen printing of nanopowders for SOFC ceramic devices is presented. Nano-powders represent the forefront of materials for SOFC. Nano-structured powders exhibit in fact important size-dependant properties such as high catalytic activity, low sintering temperatures and therefore high performances. Aim of this study is to find the correlation that link the process parameters with the nano-materials properties in order to enhance the performances and the durability both of the materials and of the final device. One of the most critical issue is to produce homogeneous and stable ceramic suspensions of nanopowders. The process optimization can be obtained merging the surface and morphological properties of the nanopowders considered (shape, dimensions' distribution, surface area, etc.) to its behavior in suspension (viscosity, zeta potential, etc.) either organic of water-based, in order to obtain a well dispersed and homogenous system. With this kind of control, it is possible to produce large area reliable devices with the necessary reproducibility and reliability