Pronounced Strain Effects on Oxygen Dissociation; Pt- or Au-Dispersed Pr₂Ni(Cu, Ga)O₄ for Active Cathode of Solid Oxide Fuel Cells

The correlation between lattice strain induced by metal dispersion into grain and the cathodic overpotential is studied for increasing oxygen-dissociation activity and improving power density of solid oxide fuel cells (SOFC) at decreased temperature. Pt or Au dispersion in Pr_1.90Ni_0.71Cu_0.21Ga_0.05O_4+d (PNCG) is prepared and the 3D tensile strain is successfully induced after sintering by a mismatch in thermal expansion coefficient. Due to higher hardness and melting temperature, Pt dispersion into bulk of PNCG introduces larger tensile strain than that by Au at the same amount. In particular, at 1 mol% Pt dispersion, large tensile strain of 0.67% is induced. Overpotential of 1 mol% Pt-PNCG cathode is 8 times smaller (35 mV) than that of PNCG (270 mV) at 800 °C and 300 mA cm⁻², and it is found that the cathodic overpotential of PNCG is decreased with tensile strain on both Pt and Au dispersion. This cathodic activity enhancement appears to be related with the increased diffusivity of oxide ion in PNCG. In this study, cathodic overpotential is more significantly influenced by the induced tensile strain comparing with the intrinsic catalytic activity of the dispersed metal.