Proton-conducting oxides offer an alternative solution for solid oxide cells with its unique advantages, such as low activation energy, high ionic conductivity at intermediate temperatures (1, 2). In the community, it is generally realized that the use of chemically stable electrolyte material BaZrO₃ is the most promising way for the development of proton-conducting solid oxide cells. Although the use of BaZrO₃ has been achieved with desirable fuel cell performance (2), the design of its air electrode is still a challenge, especially for the proton-conducting solid oxide electrolysis cells. In this presentation, we report our recent work on the tailor of the air electrode materials for proton-conducting solid oxide cell, including the use of traditional Sr-doped LaMnO3 (LSM) cathode for BaZrO₃-based fuel cells with desirable cell performance and the design of mixed proton-electronic mixing conducing air electrode for proton-conducting electrolysis cells.

LSM, which is one of the most classical air electrode materials for solid oxide cells, is regarded can be only used above 700 ^oC due to its poor catalytic activity at intermediate temperatures (around 600 ^oC). In our study, we successfully employed the inkjet printing technique, enabling LSM work properly as the air electrode for proton-conducting solid oxide fuel cells with BaZrO3 electrolyte. After the optimization, the fuel cell performance reached 200 mW cm^-2 at 600 ^oC, which is encouraging considering the air electrode material is LSM. A further improvement of fuel cell performance was achieved by using mixed electronic-oxygen conductor air electrode material, reaching the highest power output for the BaZrO₃-based cells up to now.

In addition to the work on fuel cells, research on the air electrode material for solid oxide electrolysis cells was also carried out. Following to our previous work using proton-electronic mixed conductor for proton-conducting fuel cells (3, 4), a similar strategy was proposed for electrolysis cells. Coupling BaZr_0.5Pr_0.3Y_0.2O₃ (BZPY30, a mixed protonic-electronic conductor) with La_0.6Sr_0.4Co_0.2Fe_0.8O₃ (LSCF) as the air electrode, the cell showed a dramatic electrolysis cell improvement compared with the LSCF- BaZr_0.7Pr_0.1Y_0.2O₃ (BZPY10, a pure protonic conductor). This result suggests the extension of proton conduction at the air electrode is critical for the transportation of proton at air electrode side and thus facilitates the electrochemical reactions for the proton-conducting electrolysis cells.

References

1. L. Bi, S. Boulfrad and E. Traversa, Chem. Soc. Rev., 43, 8255 (2014).

2. E. Fabbri, L. Bi, D. Pergolesi and E. Traversa, Adv. Mater., 24, 195 (2012).

3. E. Fabbri, I. Markus, L. Bi, D. Pergolesi and E. Traversa, Solid State Ionics, 202, 30 (2011).

4. E. Fabbri, L. Bi, D. Pergolesi and E. Traversa, Energ. Environ. Sci., 4, 4984 (2011).