The Oxygen Transport Properties of La2NiO4+ δ Infiltrated La0.6Sr0.4Co0.2Fe0.8O3- δ By Electrical Conductivity Relaxation

Abstract

La2NiO4+ δ(LNO) infiltration in La0.6Sr0.4Co0.2Fe0.8O3- δ (LSCF) cathodes have performed excellent cell electrochemical properties in our previous work. However, the effect of the infiltration phase on oxygen transport properties is still lacking and the mechanism for the enhancement of electrochemical properties is unclear. In this work, the electrical conductivity relaxation (ECR) is used to characterize the oxygen transport properties in La2NiO4+ δ(LNO) covered La0.6Sr0.4Co0.2Fe0.8O3- δ (LSCF)materials. The ECR experiment was performed at 700oC in different oxygen particle pressure in the range of 0.21 to 0.02 atm. The ECR data suggested that there are fast oxygen transport path along the hetero-structured interface La0.6Sr0.4Co0.2Fe0.8O3- δ (LSCF)/La2NiO4+ δ(LNO). The interface oxygen exchange coefficient k was estimated by assuming the invariable oxygen flux and the ignorable oxygen diffusion in LNO layer due to its minimal relative thickness. The calculated k value was 7.94-3.31 cm﹒s-1, which is larger than that value of the surface of single LSCF or LNO by 3-4 times. XPS analysis shown that Co and Sr diffused from LSCF into LNO layer and an additional low energy state Co peak appeared after ECR measurement resulting from Co disproportionate reaction probably, which are the possible reasons for the enhancement of surface and interface exchange coefficients.