Optimization of Ni-YSZ solid oxide fuel cell anodes by surface laser melting

Abstract

A cermet composed of a metallic component (nickel) and a ceramic matrix (yttria stabilized zirconia) is commonly used as the anode for solid oxide fuel cells (SOFC). In the present work we intend to improve the performance of Ni–YSZ anodes by surface laser melting. Symmetrical cells, consisting of two NiO–YSZ anodes (∼20 μm thickness) separated by a relatively thin YSZ electrolyte (∼500 μm) were fabricated by convectional ceramic techniques. Subsequently, laser melting treatments of both anodes were performed using a CO2 laser system, producing a NiO–YSZ eutectic lamellar microstructure. Laser power of 100 W and processing rates of 1 mm s−1 were determined as the optimum processing conditions. Symmetrical processed plates (eutectic sample) were electrically characterized by impedance spectroscopy (EIS), and the results were compared with non-processed plates (ceramic sample). Preliminary EIS results showed that the polarization resistance at higher temperatures (in the range of 900 °C) is about 0.5 Ω cm2 for both the eutectic and the ceramic sample. However, at lower temperatures (in the range of 800 °C) the polarization resistance for both samples differs considerably (2.9 and 1.6 Ω cm2 for the ceramic and eutectic sample, respectively). These experiments confirmed that optimization of the microstructure by laser surface treatment plays a crucial role in the electrochemical properties of the anode cermets.