Oxygen-Deficient Perovskite Sr_0.7Y_0.3CoO_2.65−δ as a Cathode for Intermediate-Temperature Solid Oxide Fuel Cells

Abstract

The oxygen-deficient perovskite Sr 0.7 Y 0.3 CoO 2.65−δ contains Co2O 6/2 (001) planes alternating with oxygen-deficient Co1O 1.15-δ planes having 0.15−δ O4 oxygen in the plane capping tetrahedral site Co1. With ordering of the O4 atoms below 300 °C, the oxide exhibits n-type polaronic conduction associated with localized high-spin 3d electronic configurations on Co 2+ in Co1 sites; a transition to itinerant-hole conduction occurs on disordering of O4 ions over the range 350 < T < 600 °C. Above 600 °C, Sr 0.7 Y 0.3 CoO 2.65−δ is a mixed oxide-ion/electronic conductor exhibiting good activity for the oxygen-reduction reaction, which makes it a competitive cathode material for an intermediate-temperature solid oxide fuel cell.