Coke formation and performance of an intermediate-temperature solid oxide fuel cell operating on dimethyl ether fuel

Dimethyl ether (DME) as a fuel of SOFCs is investigated with great attention paid to coke formation over the Ni-YSZ anode DME is easily decomposed to CH4 CO and H-2 at temperatures above 700 C with total conversion occurring at 850 degrees C over the Ni-YSZ catalyst These data suggest that the DME electro-oxidation likely proceeds via an indirect pathway O-2-TPO analysis laser Raman spectroscopy and SEM-EDX characterizations demonstrate coke formation over Ni-YSZ which is obvious and become more prevalent at higher temperatures The introduction of CO2 in the fuel gas decreases the CH4 selectivity and effectively suppresses coke formation above 700 C The suppression effect is increasingly apparent at higher temperatures At 850 C the anode still maintains geometric integrity after exposure to DME CO2 (1 1 volume ratio) under OCV condition With DME or DME-CO2 the fuel cell power output is comparable to results obtained by operating with 3% water humidified hydrogen No obvious cell degradation from the anode is observed when operating with DME-CO2 while it is obvious with DME The introduction of CO2 may be a good choice to suppress the coke formation when operating on DME however the proper selection of operation temperature is of significant importance (c) 2010 Elsevier B V All rights reserved