Engineering the Nano/Microstructure of Solid Oxide Fuel Cell Cathodes

Solid Oxide Fuel Cells (SOFCs)are high-temperatureelectrochemical devices that have the capacity to convert the inherent chemical energy of fuels (i.e, H₂, CO, hydrocarbons) into electrical energy. SOFCs are composed ofan anode where the fuel is electro-oxidized, an electrolyte that transports oxygen ions, and a cathode thatelectrochemically reduces gas-phase O₂ from air to oxygen ions, O^-2.In order to achieve structural stability of SOFCs at elevated, operating temperatures, the ion-conducting electrolyte oxide material is in corporated in both the anode and cathode compartments of the cell. The commonly utilized approaches for synthesizing button-cell SOFCs involve ball milling of the electrode electrocatalysts with the ion-conducting electrolyte oxide (i.e., yttria stabilized zirconia(YSZ)), and formation of the electrodes based on dry-pressing or tape casting the mixture into thin films. While these methods have led to structurally stable SOFCs, they provide limited flexibility on the incorporation of different electrocatalysts (only the ones that arestable and compatiblewith YSZ at high sintering temperatures of larger than 1000C that can be used), and lead to electrocatalyst structures that are fairly large in size (micron) with low catalytically active surface area.In this contributing, we described a method for preparing SOFC cathodes thatallow for flexibility over the cathode electrocatalyst and preservation of its nanostructure. This method relies on a controlled synthesis ofthecathode electrocatalysts with a desired nanostructure and its incorporation in a microporous scaffold of the ion-conducting oxide.We show that the developed cathode structures lead to an enhanced triple phase boundary (interface between the electrocatalyst and the ion-conducting electrolyte) and enhanced electrochemical performance.