Novel SOFC Anodes for the Direct Electrochemical Oxidation of Hydrocarbons

Abstract

Recent developments in solid-oxide fuel cells (SOFC) that electrochemically oxidize hydrocarbon fuels to produce electrical power without first reforming them to H 2 are described. First, the operating principles of SOFCs are reviewed, along with a description of state-of-the-art SOFC designs. This is followed by a discussion of the concepts and procedures used in the synthesis of direct-oxidation fuel cells with anodes based on composites of Cu, ceria, and yttria-stabilized zirconia. The discussion focuses on how heterogeneous catalysis has an important role to play in the development of SOFCs that directly oxidize hydrocarbon fuels. AbstractRecent developments in solid-oxide fuel cells (SOFC) that electrochemically oxidize hydrocarbon fuels to produce electrical power without first reforming them to H 2 are described.First, the operating principles of SOFCs are reviewed, along with a description of state-of-the-art SOFC designs. This is followed by a discussion of the concepts and procedures used in the synthesis of direct-oxidation fuel cells with anodes based on composites of Cu, ceria, and yttriastabilized zirconia. The discussion focuses on how heterogeneous catalysis has an important role to play in the development of SOFCs that directly oxidize hydrocarbon fuels.

Direct Utilization of Liquid Fuels in SOFC for Portable Applications: Challenges for the Selection of Alternative Anodes

“…Recently, the direct oxidation of hydrocarbons in SOFC has been the object of controversy [31,32]. While Gorte and Vohs [31,[33][34][35] argued that hydrocarbons can be directly oxidized using ceria-based electrodes, according to Mogensen et al [32], only H 2 is oxidized on Ni-YSZ anodes fed with dry hydrocarbons because the oxidation of methane and other hydrocarbons is significantly slower than that of H 2 . Consequently, hydrocarbon cracking, reforming and WGS reactions are likely to happen at a much faster rate, producing H 2 that is the actual electrochemical fuel of the SOFC.…”

Carbon-based Fuel Cell

“…Comparison of CH 4 I-V curve in Fig. 2 with those in literature (7)(8)(9)(10)(11)(12)(13)(14)(15) shows that the current density for CH 4 is about 35% of the best reported data for the direct methane SOFC. This is due to the use of thicker solid YSZ electrolyte (i.e, 1 mm in thickness) in our fuel cell as compared with 50 µm in the literature.…”

The effect of synthesis gas composition on the performance of Ni-based solid oxide fuel cells

“…As nickel is considered an active catalyst for carbon synthesis (Gorte 2003) it is suspected that decreasing the flow rate through the cell dramatically increases the residence time, resulting in carbon deposition and subsequent cell deactivation (Miao 2010, Ye 2010. This theory is supported by carbon balance calculations and time on stream measurements, which indicates a rapid but 10 reversible decrease in cell performance.…”

“…The high operating temperature presents an opportunity for a wide variety of fuels, with short chain hydrocarbons such as methane and ethane considered as the most viable fuel for use in solid oxide fuel cells due to the ease of supply and relative abundance. The use of hydrocarbons has been investigated (Zheng 1996, Singhal 2000, Ahmed 2002, Weber 2002, Gorte 2003, Goodenough 2007) with many groups researching both direct oxidation and 15 external reforming. If the hydrocarbon is either internally or externally reformed it will form a mixture of hydrogen and carbon monoxide (syngas) with various ratios depending on the hydrocarbon used.…”