PERFORMANCE OF A NOVEL HELIUM-STIRRED SOLID OXIDE FUEL CELL WITH MOLTEN METAL ANODE FOR ELECTRICITY GENERATION AND OXYGEN DISSOLUTION IN MOLTEN METAL

Abstract

 A novel helium-stirred solid oxide fuel cell (SOFC) with a molten metal anode for electricity generation and oxygen dissolution in a molten metal was investigated. This SOFC configuration employs conventional cathode and electrolyte but incorporates a molten metal contained in an alumina crucible as anode and inert gas stirring of the molten metal. Tin was the metal used in this study because it is non-toxic and inexpensive, it also has a relatively low melting point and very low vapour pressure at high temperatures. The performance of a SOFC with molten tin anode at 850 oC was evaluated by the techniques of electrochemical impedance spectroscopy, cyclic voltammetry and chronoamperometry. A peak power density of ca. 100 W m-2 at a potential difference of ca. 0.45 V and current density of ca. 222 A m-2 was achieved. Impedance spectra showed that ohmic potential losses controlled the reactor performance, with about 59% of those arising from the inherent difficulty in achieving a low resistance contact at the silver wire (silver wool) current collector | cathode interface. The molten metal bath provided a relatively large reservoir of molten metal for oxygen absorption and transport compared to a thin film of molten metal while gas stirring of molten metal enhanced the transport of dissolved oxygen atoms from the yttria stabilized zirconia (YSZ) electrolyte | molten metal interface to the bulk molten metal and assisted in preventing oxide formation at the YSZ electrolyte | molten metal interface.