The Morphology and Electrochemical Properties of Pt and GDC Nano Composite Films Using Co-Sputtering Method

Wednesday, 8 October 2014: 09:20
Expo Center, 2nd Floor, Gama Room (Moon Palace Resort)
Y. H. Lee (Seoul National University, School of mechanical and aerospace engineering), S. W. Cha (Mechanical and aerospace engineering department, Seoul National University), G. Y. Cho (School of mechanical and aerospace engineering, Seoul national university), S. Ji (Graduate School of Convergence Science and Technology (GSCST), Seoul National University), J. Park (Seoul National University, School of mechanical and aerospace engineering), and I. Chang (Graduate School of Convergence Science and Technology, Seoul National University)
Solid oxide fuel cell (SOFC) has a potential of next generation energy conversion device for high energy conversion rate and clean emission. However it requires high temperature above 800oC due to low kinetics of electrolyte and electrode materials. Lowering operating temperature to 400~600oC allows high system stability, various material selection, fast start-up and convenient sealing. There were several studies to lower the operating temperature with structural and material approach. Among these, application of nano fabrication to electrode and electrolyte is one of the most promising candidates because thickness of electrolyte and TPB density of electrodes are strongly affects to the cell performance. 

Up to now, several structures and materials for low temperature operation have been presented however, PVD based nano-porous Pt is dominantly used for cathode because conventional mixed conducting oxides shows poor electronic conduction and large overpotential at a certain temperature between 400~600oC. 

Pt electrodes for LT-SOFCs are usually fabricated by physical vapor deposition (PVD) to increase TPB density because it can easily control grain and pore size into nanometer scale. However increased surface energy and mobility of nano sized Pt accelerates coarsening even at a low temperature operation.

 In a metallurgical research area, several methods to enhance heat resistance of metals and one of the most effective methods are known as dispersion hardening. By uniform dispersion (<1% by weight) of thermally stable oxide nano particles (<50nm) in to metals, it prevents thermal degradation even in a high temperature.

In this research we used GDC as a dispersion oxide material to enhance physical and electrochemical property of Pt because it has high ionic conductivity and electronic conductivity among oxide electrolytes.

Pt & GDC nano composite electrodes were fabricated under co-sputtering using Pt and GDC target. 50mtorr of argon background gas pressure was maintained during sputtering and various sputtering power between 50~200W on Pt and GDC were applied to differentiate the composition.

Fabricated electrodes are treated at 500oC for an hour to characterize morphological change and analyzed by electron scanning microscopy. Finally, fabricated electrodes are applied into YSZ pellet and evaluated electrochemical properties.