NICKEL PATTERN ANODES FOR STUDYING SOFC ELECTROCHEMISTRY

摘要

The SOFC anode is a complex 3D structure where the gas phase, ionic phase and electronic phases are intermingled. This not only makes it difficult to quantify the triple phase boundary (TPB) length exactly, but also makes individual processes like charge transfer, diffusion, surface diffusion etc, difficult to localise and study. Pattern electrodes offer the advantage of having a well defined TPB length, so that reactions are localised. Impedance spectroscopy on pattern electrodes can provide mechanistic information in addition to identifying rate limiting steps. In this work nickel is sputtered on YSZ with DC magnetron sputtering using a Nickel target and a metallic mask on YSZ substrate in a specific pattern to give a well-defined TPB length. A TPB length of 0.2027 m/cm~2 was achieved. This method is much easier and is less expensive than the photolithographic techniques used earlier (Bieberle et al ETH Zurich, Mizuzaki et al Yokohama national University and Boer de et al University of Twente). Impedance spectroscopy is carried out on symmetrical cells in pure hydrogen with 4.3 % water vapour. Preliminary results from equivalent circuit fitting of the impedance spectra indicate that the results are comparable to results available in literature and the rate limiting mechanisms can be identified.