EVALUATION OF THE EFFECTIVE REACTION ZONE AT NI(NIO)/ZIRCONIA ANODE BY USING AN ELECTRODE WITH A NOVEL STRUCTURE

The effect of nickel film thickness and the thickness of a porous ceramic layer, covering the Ni film, on anode polarization of a solid oxide electrolyte fuel cell was measured at around 1273 K. The electrode impedance was found to be dependent on the thickness of the porous layer but not on that of Ni film. DC polarization was affected by the thickness of neither film at relatively high partial pressure of hydrogen. The interface resistance, R(1), obtained from the impedance plot consisted of a reaction resistance, R(1), and a diffusion resistance, R(2), caused by the porous ceramic layer. R(1) was proportional to p(H2O)(-1/2) but was not affected by P-H2. These results suggested that the rate-determining process is an activation one and it takes place at very thin zone of the Ni film within 1 mu m from the electrode/electrolyte interface. P-H2 and P-H2O dependencies of the current-voltage relation were similar to that obtained from a Ni patterned electrode and a Ni-YSZ cermet electrode by other researchers.