January 30, 2008
Conference Paper

EVOLUTION OF NI-YSZ MICROSTRUCTURE AND ITS RELATION TO STEAM REFORMING ACTIVITY AND YSZ PHASE STABILITY

Abstract

Internal steam reforming of methane within solid oxide fuel cells (SOFC) offers a method of improved thermal management and reduced system complexity. Thermal gradient management is dependent upon controlling the reforming activity along the length of the anode. The inherent activity of Ni-YSZ for the steam reforming of methane is highly dependent upon the pretreatment and reduction procedures employed. During reductive pretreatment of the anode, small Ni crystallites can exolve from the YSZ to provide a significant component to the initial catalytic activity. This activity decreases with time as the small Ni crystallites sinter. Control of this microstructure is key to controlling the thermal gradients along the anode. NiO initially dissolved in 5YSZ increases the amount of undesirable monoclinic phase, and the exolution of Ni crystallites during reduction results in a reduction in the monoclinic phase. With 8YSZ, nickel also dissolves and exolves from the YSZ particles but no monoclinic phase is observed.

Revised: June 2, 2010 | Published: January 30, 2008

Citation

King D.L., J.J. Strohm, and P. Singh. 2008. EVOLUTION OF NI-YSZ MICROSTRUCTURE AND ITS RELATION TO STEAM REFORMING ACTIVITY AND YSZ PHASE STABILITY. In Solid Oxide Fuel Cells: Ceramic Engineering and Science Proceedings, edited by P Singh, NP Bansal and T Ohji, 29, 159-172. Hoboken, New Jersey:Wiley. PNNL-SA-58926.