Improved electrochemical activity and stability of LaNi_0.6Fe_0.4O_3-δ cathodes achieved by an in-situ reaction

A simple strategy has been exploited to synergistically improve the oxygen reduction reaction (ORR) activity and stability of LaNi_0.6Fe_0.4O_3-δ (LNF) cathodes for solid oxide fuel cells (SOFCs) via in-situ infiltration of a Ba_0.5Sr_0.5CoO_3-δ (BSC) precursor on the LNF backbone. The chemical compatibility, electrochemical performance, morphology, and stability of the as-prepared composite electrodes were systematically investigated. BSC infiltration at appropriate loadings was found to be beneficial for the reduction of the polarization resistance of the LNF electrode. BSC overload resulted in an increase of the adsorption resistance, which deteriorated the ORR performance of the LNF cathode. The calcination temperature of the BSC precursor was found to be a key parameter for the morphology as well as the electrochemical performance of the hybrid composite cathode. For the cathode calcined at 900 °C, BSC nanoparticles diffused into the LNF scaffold through high temperature reaction sintering. Moreover, the stability tests at 750 °C for 80 h in air revealed that the LNF cathode coated with a hybrid La(Ba,Sr)Ni(Fe,Co)O_3-δ thin film through in-situ reaction sintering was far more stable than the counterpart infiltrated with nanoparticles. This strategy via surface modification through an in-situ high temperature reaction may be extended to other electrode systems for SOFCs.