High Performance Air Electrode for Solid Oxide Regenerative Fuel Cells Fabricated by Infiltration of Nano-Catalysts

A high performance air electrode fabricated by infiltration of highly active nano-catalysts into a porous scaffold is demonstrated for high-temperature solid oxide regenerative fuel cells (SORFCs). The nitrate precursor solution for Sm_0.5Sr_0.5CoO₃ (SSC) catalyst is impregnated into a porous La_0.6Sr_0.4Co_0.2Fe_0.8O₃ (LSCF) – gadolinia-doped ceria (GDC) composite backbone, and extremely fine SSC nano-particles are uniformly synthesized by in-situ crystallization at the initial stage of SORFC operation via homogeneous nucleation induced by urea decomposition. The SSC nano-catalysts are in the size range of 40-80 nm and stable against coarsening upon the SORFC operation at 750^oC. The electrochemical performance is significantly improved by incorporation of SSC nano-catalysts in both power generation and hydrogen production modes. Systematic analysis on the impedance spectra reveals that the surface modification of the air electrode with nano-catalysts remarkably accelerates the chemical surface exchange reactions for both O₂ reduction and O^2- oxidation, which are the major limiting processes for SORFC performance.