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RESEARCH PRODUCT

Protonic ceramic fuel cell : elaboration and characterization. Investigation of the BaZr0.8Y0.2O3-d electrolyte by electrochemical impedance spectroscopy

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One of the current global challenges is to find novel, clean and efficient techniques for the energy production. The use of electrochemical cells and hydrogen is one of the solutions. These cells convert the excess energy produced by conventional systems into hydrogen by steam electrolysis. The hydrogen can be stored and transformed into electricity when needed in the fuel cell mode. Among the different electrochemical cells, protonic ceramic electrochemical cells have attracted much attention due to their high efficiency at intermediate temperature (400 – 600 °C). In addition, these systems offer the advantage of not diluting the fuel in electrolysis mode. This thesis work focuses on the electricity production, i.e., on the protonic ceramic fuel cell (PCFC). The protonic conductor material BaZr0.8Y0.2O3-δ was produced at low temperature (400 °C) under a pressure of 300 bar by hydrothermal synthesis. Two variants of the process were evaluated: a batch and a continuous system. In addition to exhibit greater productivity (6 g.h-1), the continuous process allows the elaboration of a better quality material in terms of stability and conductivity (evaluated by electrochemical impedance spectroscopy). PCFCs were also produced during this work. The anode, composed of Ni and BaZr0.8Y0.2O3-δ, was elaborated by tape casting. The electrolyte (BaZr0.8Y0.2O3-δ) by reactive DC sputtering. Finally, the cathode, a BaZr0.8Y0.2O3-δ-Ba0.5Sr0.5Co0.8Fe0.2O3-δ ceramic composite, was deposited by spray using an airbrush. This manufacturing process allows the production of an electrochemical cell with a fine electrolyte (5 µm) and a columnar microstructure allowing the ohmic resistance to be lowered to 7 Ω.cm-2 at 525 °C.