Oxygen–Reduction Reaction on Preferred Oriented Gd0.1Ce0.9O2−δ Films

Abstract

Oxygen–reduction reaction (ORR) on Gd0.1Ce0.9O2−δ (GDC) films with preferential orientations of [100] and [111] have been investigated by using electrochemical impedance spectra combined with direct current (DC) bias. Without DC bias, apparent activation energy for ORR is 0.43 eV on GDC(100) and 1.37 eV on GDC(111). When negative bias increases from 0 to 0.250 V, apparent activation energy for ORR on either GDC(100) or (111) initially increases, attains the maximums of 1.6 eV on GDC(100) and 1.65 eV on GDC(111) and then decreases linearly with the slope of −2.18 eV/V on GDC(100) and −5.17 eV/V on GDC(111). On GDC(100), reaction rate of the key rate-determining step (RDS) exhibits oxygen pressure-dependent exponents of 0.439 under open circuit voltage (OCV) conditions and 0.379 under 0.150 V negative bias, whereas on GDC(111), reaction rate of the key RDS exhibits oxygen pressure-dependent exponents of 0.397 under OCV conditions and 0.177 under 0.150 V negative bias.