The impact of biomass-derived contaminants on solid-oxide fuel cells ͑SOFCs͒ with Ni/gadolinia-doped ceria ͑GDC͒ anodes was investigated using electrochemical impedance analysis. Measurements were carried out with symmetric test cells under a singlegas atmosphere. The impact of H 2 S, HCl, and naphthalene in the gas stream on the performance of Ni/GDC anodes are presented. No significant impact has been observed up to 9 ppm H 2 S and HCl and 110 ppm naphthalene. © 2007 The Electrochemical Society. ͓DOI: 10.1149/1.2820452͔ All rights reserved. Gasification is the conversion of biomass to a gaseous fuel by heating in a gasification medium such as air, oxygen, or steam. Biosyngas from gasification consists of a mixture of carbon monoxide, carbon dioxide, methane, hydrogen, water vapor, and impurities. These impurities are mainly ͑i͒ particulate matter, ͑ii͒ tar, ͑iii͒ alkali metal compounds and other halides, ͑iv͒ sulfur compounds, and ͑v͒ nitrogen-containing compounds, especially ammonia. Once the biosyngas is cleaned to remove the contaminants to a level sufficient for solid oxide fuel cells ͑SOFCs͒, it can probably be used as an SOFC fuel.1,2 As the biomass is a sustainable primary energy source and is essentially CO 2 neutral, such systems offer the potential for sustainable high-efficiency energy systems for the future.Feeding SOFCs with biosyngas draws attention to many important issues. Because the fuel gets oxidized at the SOFC anode, chemical and physical interactions between the anode and the gas components are of critical significance. Different types of anodes have different kinds of interactions with these contaminants, and hence their tolerance levels for these contaminants may vary considerably. This, in turn, alters the choices for the required gascleaning devices when SOFCs with such anodes are connected to biomass gasifiers. Because these different types of anodes may have varying effectiveness in the conversion of the fuel, proper selection of the SOFCs with suitable anodes and gas-cleaning systems and appropriate operation parameters for them is of critical significance in the development of feasible and efficient designs of biomass gasifier-SOFC systems.Conventional SOFC anodes contain substantial amounts of nickel. Nickel is widely considered as an attractive material for SOFC anodes because it is a good electronic conductor and catalytically active for the electrochemical oxidation of hydrogen. In order to increase the mechanical properties, nickel is mixed with an ionconducting material, most commonly yttria-stabilized zirconia ͑YSZ͒. Doped ceria, such as gadolinia-or samaria-doped ceria, is a mixed conductor under reducing conditions. It offers increased surface area for electrochemical reactions, unlike materials offering mainly ionic conductivity and low electronic conductivity, which limit the reactions to fuel/electrode/electrolyte boundaries. They are also expected to give better performance with fuels containing hydrocarbons.3 For this reason, anodes comprising gadolinia-doped ceria ͑...

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The combination of biomass gasification systems with fuel cells promises adequate systems for sustainable, decentralized energy conversion. Especially high temperature fuel cells are suited for this task because of their higher tolerance to impurities, their internal steam reforming potential, and favorable thermal integration possibilities. This paper presents the results of biosyngas utilization in solid oxide fuel cells with Ni∕GDC anodes at 850 and 920°C. The relation between the fuel composition and the electrochemical performance is discussed, as well as the impact of sulfur up to a concentration of 9ppmH2S. The investigations have made clear that Ni∕GDC anodes can be operated within a wide range of biosyngas compositions. Sulfur has appeared to deactivate the anode for methane reforming. The oxidation of hydrogen and carbon monoxide are insensitive to sulfur, suggesting that both nickel and GDC are active electrocatalysts.

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