Journal of Power Sources 157 (2006) 750–753 Short communication Formulating liquid ethers for microtubular SOFCs Kevin Kendall ∗ , Matthew Slinn, John Preece Chemical Engineering, University of Birmingham, Edgbaston B15 2TT, UK Received 14 October 2005; received in revised form 16 January 2006; accepted 23 January 2006 Available online 28 February 2006 Abstract One of the key problems of applying solid oxide fuel cells (SOFCs) in transportation is that conventional fuels like kerosene and diesel do not operate directly in SOFCs without prereforming to hydrogen and carbon monoxide which can be handled by the nickel cermet anode. SOFCs can internally reform certain hydrocarbon molecules such as methanol and methane. However, other liquid fuels usable in petrol or diesel internal combustion engines (ICEs) have not easily been reformable directly on the anode. This paper describes a search for liquid fuels which can be mixed with petrol or diesel and also injected directly into an SOFC without destroying the nickel anode. When fuel molecules such as octane are injected onto the conventional nickel/yttria stabilised zirconia (Ni/YSZ) SOFC fuel electrode, the anode rapidly becomes blocked by carbon deposition and the cell power drops to near zero in minutes. This degeneration of the anode can be inhibited by injection of air or water into the anode or by some upstream reforming just before entry to the SOFC. Some smaller molecules such as methane, methanol and methanoic acid produce a slight tendency to carbon deposition but not sufficient to prevent long term operation. In this project we have investigated a large number of molecules and now found that some liquid ethers do not significantly damage the anode when directly injected. These molecules and formulations with other components have been evaluated in this study. The theory put forward in this paper is that carbon–carbon bonds in the fuel are the main reason for anode damage. By testing a number of fuels without such bonds, particularly liquid ethers such as methyl formate and dimethoxy methane, it has been shown that SOFCs can run without substantial carbon formation. The proposal is that conventional fuels can be doped with these molecules to allow hybrid operation of an ICE/SOFC device. © 2006 Elsevier B.V. All rights reserved. Keywords: Microtubular SOFC; Ether fuels; Carbon deposition on anode; Hybrid ICE/SOFC 1. Introduction Present-day fuels, such as gasoline, kerosene or diesel, have largely been developed for internal combustion engines (ICEs) and are specified by octane or by cetane numbers which depend on ignition and oxidation characteristics. Fuels have not yet been specifically defined for solid oxide fuel cells (SOFCs), which demand electrochemical reactivity on catalytic anodes. Conse- quently there is a problem when standard fuels are used in an SOFC because the fuel cell power drops to near zero in a few minutes under ordinary circumstances when normal fuels like gasoline are injected directly into a fuel cell anode [1,2]. An extensive literature on this effect exists, explaining the anode destruction in terms of carbon deposition on the nickel [13]. ∗ Corresponding author. Tel.: +44 1214142739; fax: +44 1214145377. E-mail address: k.kendall@bham.ac.uk (K. Kendall). Because SOFCs operate between 600 and 1000 ◦ C, they have potential to utilise hydrocarbons such as methane or natural gas and liquid fuels such as gasoline and kerosene [3,4]. However, the commonly used nickel/yttria stabilised zirconia (Ni/YSZ) anode tends to block with carbon when hydrocarbons are used, although steam reforming or partial oxidation can alleviate this problem [5,6]. It has been established that certain molecules without C C bonds such as methane, methanol and methanoic acid deposit much less carbon on the nickel/zirconia than longer chain C C molecules like octane and therefore can be used directly in an SOFC [6,7]. The purpose of this paper is to extend that study of gases, alcohols and organic acids to include ethers and more complex potential fuel molecules. In particular we show that molecules containing no C C bonds such as methyl formate or dimethoxy methane are interesting liquid fuels for direct injection into SOFCs [8]. This suggests that a hybrid internal combustion engine (ICE) could run on a hybrid fuel such as diesel doped with the ether, which could be separated to operate the SOFC. One way in which this could be achieved 0378-7753/$ – see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.jpowsour.2006.01.061