Infiltration of electrocatalysts into ionic conducting backbones (e.g. Sr – doped LaCoO3 (LSC) into Ce0.9Gd0.1O1.95 (CGO)) is becoming a widely popular means of preparing composite cathodes for SOFCs. The high surface area nanoparticle grains of the electrocatalyst obtained using the method enhances the available area for oxygen surface exchange. However, during long term operation, the nanoparticles exhibit significant grain growth and subsequent loss of percolation thus increasing both the ohmic (Rs) and polarization (Rp) resistance. Here, we present a way to mitigate the problem by doping the CGO backbone with Pr through infiltration into the structure followed by firing. The Pr – modified CGO backbone is then infiltrated with LSC. The electrochemical performance of the infiltrated cathodes with and without Pr modification in the backbone was studied by impedance spectroscopy on symmetric cells during 1000 h operation and under varying firing temperatures. It is found that the cathodes with Pr – modified backbones exhibit lower Rp and are more tolerant to heat temperature treatments as evidenced by the lesser increase in Rp and Rs at 600 °C after heating at a maximum temperature of 900 °C (without Pr: Rp from 0.094 to 0.45 Ω cm2, Rs from 0.74 to 0.79 Ω cm2; with Pr: Rp from 0.051 to 0.32 Ω cm2, Rs from 0.74 to 0.71 Ω cm2). The improved performance and heat treatment tolerance is thought to originate from the imparted electronic conductivity into the CGO backbone by introducing Pr.
Proceedings of 38th International Conference and Expo on Advanced Ceramics and Composites (icacc-38), 2014
Infiltration; Cathode; Solid Oxide Fuel Cells
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38th International Conference and Expo on Advanced Ceramics and Composites, 2014