Synthesis of 3-dimensional silver networks and their application in solid oxide fuel cells

The synthesis of 3-dimensional silver metal structures for use in solid oxide fuel cells (SOFCs) as current collectors and cathodes for the oxygen reduction reaction (ORR) by screen printing and sintering of Ag2O particles is presented. The microstructure of the silver thus obtained was found to depend on the processing temperature, with lower sintering temperatures resulting in greater porosity and surface area. The silver current collectors was found to undergo steam embrittlement during SOFC operation, but the embrittlement could be prevented by pre-treating the silver metal with N2 gas at high temperatures (800 °C) or with 10% H2-90% Ar at room temperatures (∼25 °C). An investigation of the polarization resistances of these silver samples by employing them as cathodes for ORR on symmetric cells indicate that the samples with greater porosity show diminished performance, confirming that the rate limiting step for the silver cathodes is oxygen transport. These silver cathodes were also compared to similarly-prepared platinum cathodes, and the silver cathodes were observed to have drastically reduced polarization resistances.