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.