Rapid porosity formation of silver under SOFC conditions in methane-oxygen mixed gas

Solid silver (Ag) is widely used current collector for solid oxide fuel cells (SOFCs). Here, its structure stability is examined in methane-oxygen mixed gas at a furnace temperature range of 600–750 °C. Rapid porosity formation is observed for solid Ag samples, especially in the presence of Ni/yttria-stabilized zirconia (YSZ) anode materials. This is mainly attributed to simultaneous diffusion of hydrogen, carbon monoxide and oxygen into Ag bulk, followed by subsequent interaction resulting in the formation of water and carbon dioxide gas. The obtained results demonstrate that partial oxidation of methane and the formation of hydrogen and carbon monoxide play an important role in the rapid porosity formation of Ag under the above specified operating conditions. Furthermore, the porosity formation of Ag samples is closely related to methane-oxygen-ratio (R_mix) and operating temperatures.