Enhancement of high temperature metallic catalysts: Aluminum titanate in the nickel-zirconia system

Abstract

Solution infiltration remains limited in its advantage for processing metallic catalysts given the propensity at high temperatures for nanometer scale materials to coarsen at rates far exceeding classic systems. Using SOFC anodes as a model system, this study examines how aluminum titanate as an additive to a porous Ni/YSZ cermet anode stabilizes a network of sub-micron nickel electrocatalysts formed from solution infiltration. Temperature dependent secondary phase formation is studied with XRD and Raman. Spatial evolution of the secondary phases that form is quantified using SEM/TEM/EDX to establish the species present during the thermal activation process. Finally, these results are used to fabricate SOFC membrane electrode assemblies, demonstrating the ease with which aluminum titanate can be added to nickel catalyst systems and the efficacy of the doping process. Current density and EIS measurements indicate that using aluminum titanate as an anode additive dramatically increases catalyst stability such that the time required for degradation to 90% of initial current output was increased by a factor of 115 for modified catalysts.