Solid oxide fuel cell with NiCo–YSZ cermet anode for oxidation of CO/H2 fuel mixtures

The suggestion has been made in the literature that solid oxide fuel cells (SOFCs) operated with syngas as fuel may be viable in certain gas ratio regimes. We have explored this hypothesis with a promising bimetallic anode material. SOFCs with Ni0.7Co0.3–YSZ cermet anodes were operated with CO/H2 mixtures in the full concentration range. Electrochemical impedance spectroscopy and voltammetry measurements were employed to measure the exchange current density (i0) values of each fuel mixture. The fuel mixtures of CO/H2 ratios corresponding to the range 20/80 and 30/70 were found to have i0 values larger than that of pure H2 with the same cell. For these two fuel ratios, an improvement of 5–8 times, respectively, in the exchange current density has been observed. Higher CO/H2 fuel ratios in the range of 60/40–80/20 produced i0 values lower than H2, as carbon poisoning is operational in this region. Continuous running of a cell with fuel ratio 25/75 CO/H2 for 7 days produced i0 values above the values for pure H2 as has been recently suggested.

► Ni0.7Co0.3–YSZ anodes offer enhanced resistance to carbon poisoning under syngas.
► A CO/H2 ratio of 20/80 offers improvement in the exchange current density.
► Ni–Co alloy allows parallel oxidation of H2 and CO for optimal performance.