An investigation of the oxygen reduction reaction mechanism of La0.6Sr0.4Co0.2Fe0.8O3 using patterned thin films

Lanthanum strontium cobalt iron oxide (La0.6Sr0.4Co0.2Fe0.8O3) thin films deposited by pulsed laser deposition on single crystal yttria stabilised zirconia (YSZ) substrates were lithographically patterned to produce geometrically well defined micro-cathodes. LSCF cathode designs varying in surface area between 0.038 cm2 and 0.267 cm2 were electrochemically tested for investigation of the oxygen reduction reaction. A gold current collector geometry was used whilst controlling the LSCF surface area and three-phase boundary lengths. The oxygen surface exchange reaction was identified as the rate limiting step between 400 °C and 500 °C. Below 400 °C, the ASR appeared to be more sensitive to changes at the LSCF surface, possibly due to slower reaction kinetics but the effect of the surface pathway could not be deemed negligible. However, the effect of the microfabrication processing on the oxygen surface exchange properties of the patterned LSCF micro-cathodes cannot be deemed negligible. Degradation in performance scaled inversely with the patterned LSCF feature size.