Direct Electrochemical Oxidation of Hydrocarbon Fuels on SOFCs: Improved Carbon Tolerance of Ni Alloy Anodes

We show that Sn/Ni alloy anode electrocatalysts (0.5-1 wt % nominal loading of Sn with respect to Ni) exhibit improved tolerance to carbon-induced deactivation in the internal utilization of hydrocarbon fuels on solid oxide fuel cells (SOFCs) compared to conventional monometallic Ni electrocatalysts. The Sn/Ni electrocatalysts were tested in the direct electrochemical oxidation of methane and isooctane. It was observed that the electrochemical activity and electronic conductivity of Ni were not compromised significantly by introduction of Sn. We postulate that the improved carbon tolerance of Sn/Ni compared to monometallic Ni electrocatalysts is due to the formation of Sn/Ni surface alloys, which, unlike monometallic Ni, preferentially oxidize carbon atoms and fragments, removing these from the surface of the electrocatalyst rather than forming carbon-carbon bonds. (C) 2009 The Electrochemical Society. [DOI: 10.1149/1.3208060] All rights reserved.