Wednesday, 16 October 2019: 14:30
Room 222 (The Hilton Atlanta)
Solid oxide fuel cells anodes are typically composed of a porous nickel-yttria stabilized zirconia (Ni-YSZ) ceramic metallic (cermet) composite. The advantages of a Ni-YSZ anode are many: the materials are inexpensive, Ni is an exceptionally effective CH bond activation catalyst and these electrodes can operate with a wide variety of fuels. However, Ni-YSZ anodes are also susceptible to material degradation and deteriorating device performance, especially when subjected to repeated reduction/oxidation cycling and/or carbon accumulation and metal dusting. Recent work in our laboratory has sought to improve the durability and resilience of Ni-YSZ anodes by adding small amounts of secondary materials to the anode stock prior to fabrication and processing. One secondary material that has proven particularly effective is aluminum titanate (Al2TiO5or ALT) During anode processing, ALT (4% by mass) reacts with Ni-YSZ to form nickel aluminate (NiAl2O4) and zirconium titanate (Zr5Ti7O24). Upon anode reduction, NiAl2O4 forms Ni particles decorated with Al2O3 nanoparticles. These secondary phases improve device performance and appear to preserve anode microstructure even after 100 hours of continuous operation. Furthermore, these secondary phases enhance anode resilience to redox cycling. We have used a variety of electrochemical and operandooptical methods to test the resilience of ALT-enhanced anodes subject to both electrochemically-induced oxidative stress and environmentally driven anode oxidation. In both cases, ALT-enhanced anodes can withstand more than twice as many redox cycles as anodes that have not had ALT added. In addition, adding ALT to the anode reduces its susceptibility to carbon accumulation when operating with hydrocarbon fuels.
