First-Principles Analysis of the Activity of Transition and Noble Metals in the Direct Utilization of Hydrocarbon Fuels at Solid Oxide Fuel Cell Operating Conditions

The direct, on-cell use of hydrocarbon fuels in solid oxide fuel cells (SOFCs) involves many thermo-chemical and electro-chemical reactions that occur on anode electro-catalysts, both at and away from the three-phase boundary (TPB). We have used first-principles density functional theory calculations and kinetic modeling to investigate relevant reactions associated with the direct utilization of methane on different electro-catalysts at SOFC operating conditions. These studies allowed us to compare the relative activity of different metals and identify those metals that offer optimal performance. Our analysis shows that under relevant operating conditions there exists a family of metals (mainly Ni, Co, Rh, Ru, Ir) that offer maximum activity for all relevant reactions. The findings suggest that a fairly simple anode design including only one material in combination with YSZ performing multiple reactions should offer close to optimal performance. While we outline in detail our results for methane, we also comment on the direct utilization of other hydrocarbons.