Lanthanum silicate-based layered electrolyte for intermediate-temperature fuel cell application

An oxide ion (O2−) conducting membrane cell, based on lanthanum silicate oxyapatite (La9.33+xSi6O26+1.5x, LSO), exhibiting low ohmic and polarization resistances in the intermediate-temperature region (~873 K) was developed. As a solid electrolyte, highly conductive Mg-doped LSO, La9·8(Si5·7Mg0.3)O26.4 (MDLS), modified with another kind of non-conductive lanthanum silicate, La2SiO5 was employed. Two kinds of silicate layers were successively spin-coated on a Ni-MDLS porous anode support, followed by thermal treatment aimed at improving ionic conductivity as well as densification of MDLS through solid state reactive diffusion. In addition, the Gd-doped CeO2, (Ce0.9Gd0.1)O1.95 (GDC) electrolyte layer, which plays an important role to prevent a reaction between the electrolyte and cathode materials, was spin-coated on the modified MDLS electrolyte. Finally, the cathode layer of porous (La,Sr)(Co,Fe)O3-δ was screen printed on the electrolyte layers. The resulting cell obtained from this study showed good fuel cell performance with a maximum power density of 94 mW cm−2 at 873 K, when operated with argon-diluted hydrogen and pure oxygen gasses. •Oxide ion conducting cell with low ohmic and polarization resistances was developed.•Dense lanthanum silicate film grows through solid state reactive diffusion.•Interfacial impurity phase was detected using synchrotron radiation microbeam XRD.