NOVEL METHODS OF MANUFACTURING SOLID OXIDE FUEL CELL ELECTRODES

A solid oxide fuel cell (SOFC) is an electrochemical device that converts chemical energy of a fuel (hydrogen) directly into electrical energy. The chemical energy from hydrogen and an oxidant (oxygen) is converted without combustion to the electrical energy. The hydrogen fuel is supplied to the anode while oxygen enters through the cathode into the fuel cell. With the use of a catalyst the hydrogen atom separates into a proton and an electron and both of these take different routes through the system into the cathode.

SOFCs are an important strand of future hydrogen/ electrical energy provision. They offer high efficiency, compactness and little pollution. However, their necessary high operating temperatures place severe demands on the component materials. To maximise efficiency, SOFCs operate at temperatures as high as 1000°C but since a metallic (e.g. nickel) anode and a ceramic (e.g. yttria-stabilised zirconia − YSZ) electrolyte have different coefficients of thermal expansion (CTE) values, this means that at the operating temperatures, the anode may peel away from the solid electrolyte. To release this thermal strain, adding YSZ (CTE - 10 ×10⁻⁶ K⁻¹)^[1] to the metal produces a similar CTE to that of the electrolyte.

A cost-effective way of combining the metallic and ceramic parts of the anodes is the principal driving force of this paper and involves electroless plating of YSZ with nickel. The two components − both in powdered form − are then processed by either cold pressing or screen printing - followed by vacuum sintering. Their performance − in terms of electrical conductivity, micro-structural uniformity and density will be presented and discussed.