Influence of the Solid Oxide Electrolysis Component Characteristics on the Electrochemical Performance of SOE Cells

Four solid oxide electrolysis cells (SOEC) with different cathode microstructure and chemical composition (Ni-YSZ and Ni-GDC) and electrolyte thickness (ScSZ) have been prepared using tape casting and screen printing methods. Electrochemical performance of the single cells at various working temperatures and gas mixtures in the cathode compartment has been analyzed using cyclic voltammetry, impedance spectroscopy and other electrochemical methods. It was established that the ratio of the rate-determining steps (mass transfer, charge transfer and adsorption of intermediates and fuel products) changes from mixed kinetics process at 1 V (solid oxide fuel cell regime) towards mainly the diffusion (δ = -45°) limited process at 1.4 V (electrolysis regime).  It was shown that the total polarization resistance decreases with the replacement of Ni-YSZ to Ni-GDC. The lowest total polarization resistance (and highest current density values) has been measured for single cell consisting on the supportive ScSZ electrolyte and thin Ni-GDC cathode layer.