Synthesis and characterization of nanocomposite Ni-YSZ anodes by water-in-oil micro-emulsion for solid oxide fuel cells

Abstract

Homogeneously distributed nanocomposite Nickel oxide-yttria stabilized zirconia (NiO-YSZ) powders were synthesized by water-in-oil (W/O) micro-emulsion method for solid oxide fuel cells. The particles synthesized by W/O micro-emulsion procedure with the calcination temperature of 500 oC, showed fine microstructures with a particle size less than 50 nm. Electrochemical performances were improved by the nanocomposite anode synthesized by micro-emulsion, compared with the results obtained by the conventional anode. The maximum power density of a single cell with micro-emulsion synthesized Ni-YSZ anode showed a higher maximum power density, 359 mW cm-2, compared with that of a single cell composed of conventional Ni-YSZ anode, 204 mW cm-2, at the operating temperature of 850 oC. The electrode resistance of a single cell fabricated by micro-emulsion had a value of 0.44 Ω cm2, which was much smaller than the value of conventional cell, 1.14 Ω cm2, at the same operating temperature with I-V analysis. The enlarged TPB length obtained by the microemulsion synthesized Ni-YSZ anode composed of uniformly distributed nano-grains might be the reason of the improved electrochemical performance of a single cell. Further studies were done to optimize the micro-emulsion procedures for improved cell performances. Three types of micro-emulsion synthesized NiO-YSZ powders, W10N10, W5N15, W0N20, with different alkali concentrations, were discussed. Particle size of W0N20 decreased to 30nm compared with the value of W10N10, around 40nm. Moreover, specific surface area of W0N20 drastically increased to 42.27 m2/g, from the value of W10N10, 14.98 m2/g. However, the maximum power density of a single cell was not affected by the alkali concentrations. The electrode resistance of a single cell with W0N20 showed a higher value of 0.65 Ω cm2, compared with the value of a single cell with W10N10, 0.44 Ω cm2, at the open circuit voltage with the operating temperature of 850 oC, although the particle size of W0N20 is smaller than that of W10N10. The reduced TPB length caused by the agglomeration of too small particles might be the reason of the electrochemical performances of single cells. ⓒ 2017 DGIST