Control of microstructure, sinterability and performance in Co-precipitated NiYSZ, CuYSZ and CoYSZ SOFC anodes

Abstract

Preparation of mixed metal oxide precursors for solid oxide fuel cells represents a very complex chemical process in which a metal may form oxides, hydroxides and various complex basic salts as intermediates. A detailed study to determine the relationship between synthesis strategies, morphology, sinteractivity and SOFC performance is a necessity. In this work, a direct relationship has been established between the precipitation agent, the calcination process, the final composition, particle sizes, sinterability and solid oxide fuel cell (SOFC) performance for nickel, copper and cobalt based anode materials. Nickel, copper and cobalt yttria stabilized zirconia (NiYSZ, CuYSZ and CoYSZ) anode materials were synthesized via hydrolysis of the corresponding chloride solutions with NH₃, NH₃ + NaOH and NaOH as precipitation agents. The formation pathway was established for the various products by the direct observation of intermediate species throughout the synthesis process. A comparison of the powders indicates that the choice of precipitation agent greatly influences the final characteristics. The cobalt anodes offered the highest SOFC performance, while within each metal system, the anodes with a crystalline precursor resulted in higher exchange current densities for the charge transfer portion of the impedance spectra.