Performance and Limitations of Nickel‐Doped Chromite Anodes in Electrolyte‐Supported Solid Oxide Fuel Cells

Abstract

Ni-doped chromite anodes were integrated into electrolytesupported cells (ESC) with 5 × 5 cm 2 size and investigated in fuel cell mode with H 2 /H 2 O fuel gas. Both a stoichiometric and a nominally A-site deficient chromite anode material showed promising performance at 860°C approaching the ones of state-of-the-art Ni/Gd-doped ceria (CGO) anodes. While the difference in polarization resistance was small, an increased ohmic resistance of the perovskite anodes was observed, which is related to their limited electronic conductivity. Increasing the chromite electrode thickness was shown to enhance perform-ance and stability considerably. Degradation increased with current density, suggesting its dependency on the electrode potential, and could be reversed by redox cycling. Sulfur poisoning with 20 ppm hydrogen sulfide led to rapid voltage drops for the chromite anodes. It is discussed that Ni nanoparticle exsolution facilitates hydrogen dissociation to the extent that it is not rate-limiting at the investigated temperature unless an insufficiently thick electrode thickness is employed or sulfur impurities are present in the feed gas.

Enhancing the Mechanical Strength of Electrolyte-Supported Solid Oxide Cells with Thin and Dense Doped-Ceria Interlayers

“…The maximum current density of the PVD-AS-SP-FS cell was slightly higher than the maximum current density of 0.94 A·cm –2 at 0.6 V (0.56 W·cm –2 ) of the SP-AS-FS cell. The performance was again very close to the previously reported 0.59 W·cm –2 for a cell of the PVD-AS-SP-FS type . The PVD-AS-FS cell showed a slightly lower performance of 0.87 A·cm –2 at 0.6 V (0.52 W·cm –2 ).…”

“…The performance was again very close to the previously reported 0.59 W•cm −2 for a cell of the PVD-AS-SP-FS type. 2 The PVD-AS-FS cell showed a slightly lower performance of 0.87 A•cm −2 at 0.6 V (0.52 W•cm −2 ).…”

“…The polarization resistance of all three cells is dominated by a large semicircle with peak frequencies of ∼1 Hz, which is related to the gas conversion resistance and is strongly dependent on the fuel gas phase composition. 2,20 The different values for the three cells were caused by deviations in humidity in the fuel gas compartment because of small temperature differences in the water bubbler, different leakage rates between the anode and cathode or different flow patterns in the cell housing. A lower humidity during the measurement of the PVD-AS-SP-FS was also reflected by its slightly higher OCV (Figure 2a).…”

“…However, the large thickness leads to a particularly large ohmic resistance to the ionic flow that reduces efficiency. As a consequence, the ESC performance is governed by the ohmic resistance, 2 and ESC are operated at high temperatures typically above 800 °C to obtain sufficiently high ionic conductivity and enable fast electrode kinetics. Therefore, the reduction of their electrolyte thickness and the corresponding ohmic losses show great potential to significantly increase the ESC efficiency.…”

Operational Aspects of a Perovskite Chromite-Based Fuel Electrode in Solid Oxide Electrolysis Cells (SOEC)

“…For these cells, the L65SCrN ceramic powder was supplied by Marion Technologies (Verniolle, France) as shown in Figure S2. For the transposition on a larger scale, the same formulation as that used for the symmetrical cells was produced in the kilogram range, in order to obtain a sufficient amount of powder with the same characteristics for a further study and up-scaling.…”