Synthesis and characterization of NdBaMn_1.5-xCo_0.5Nb_xO_5+δ (x=0, 0.1, 0.2) as cathode materials for IT-SOFCs

摘要

The effect of Nb substitution on structural characteristics, thermal expansion behavior, electricalproperties and catalytic activity for oxygen reduction reaction (ORR) of the layered perovskite oxidesNdBaMn1.5-xCo0.5NbxO5+δ (x=0, 0.1, 0.2) has been investigated. After doping with Nb at B-site, thethermal expansion coefficient (TEC) value of NdBaMn1.5-xCo0.5NbxO5+δ increases slightly. The averageTEC of NdBaMn1.5Co0.5O5+δ, NdBaMn1.4Co0.5Nb0.1O5+δ and NdBaMn1.4Co0.5Nb0.2O5+δ are 12.89×10-6K-1, 13.55×10-6K-1 and 13.38×10-6K-1, respectively, which are much lower than that of Co-basedlayered perovskites. The electrical conductivity of NdBaMn1.5-xCo0.5NbxO5+δ (x=0, 0.1, 0.2) samplesdecrease slightly with Nb content increasing due to the reduction of charge carriers. The doping of Nbgreatly benefits the catalytic activity for oxygen reduction reaction. The adsorption/desorption of themolecular oxygen, bulk or surface oxygen diffusion processes during the ORR are improved by Nbdoping. The Rp of NdBaMn1.4Co0.5Nb0.2O5+δ is 0.07Ωcm2 at 800°C which is triple lower than that ofNdBaMn1.5Co0.5O5+δ (0.21 Ωcm2 at 800°C ). NdBaMn1.4Co0.5Nb0.1O5+δ and NdBaMn1.4Co0.5Nb0.2O5+δsamples exhibit low thermal expansion and high catalytic activity as promising cathode materials forIT-SOFCs.