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

La₂NiO_4+δ(LNO) infiltration in La_0.6Sr_0.4Co_0.2Fe_0.8O_3-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 La₂NiO_4+δ(LNO) covered La_0.6Sr_0.4Co_0.2Fe_0.8O_3-δ (LSCF)materials. The ECR experiment was performed at 700^oC 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 La_0.6Sr_0.4Co_0.2Fe_0.8O_3-δ (LSCF)/La₂NiO_4+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.