Reaction mechanism of Ni pattern anodes for solid oxide fuel cells

Ni pattern anodes with triple phase boundary (tpb) lengths varying between 0.04 and 4 m/cm(2) were prepared by photolithography, The lines are continuous on the whole surface area of the anode and are stable during thermal treatment up to 973 K. The patterns also withstand electrochemical measurements up to moderate overpotentials of at least 200 mV. The impedance spectra consist of three semicircles and are fitted to an equivalent circuit consisting of an electrolyte resistance R-e, a charge transfer resistance R-t, a double layer capacitance C-d1, as well as three R-CPE ((C) under bar nstant (P) under bar hase (E) under bar lement) units. It is found that two electrode processes are significantly influenced by the variation of the tpb length, whereas one process stays almost constant. The polarization resistance R-p is inversely proportional to the tpb length. (C) 2000 Elsevier Science B.V. All rights reserved.