Ni-Substituted SrFeMoO as an Electrode Material for Symmetrical and Reversible Solid-Oxide Cells.

This work develops a novel perovskite SrFeNiMoO (SFNM) simultaneously using as a fuel electrode and oxygen electrode in a reversible solid oxide cell (RSOC). SFNM shows outstanding electrocatalytic activity for hydrogen oxidation, hydrogen evolution, oxygen reduction, and oxygen evolution. In situ exsolution and dissolution of Fe-Ni alloy nanoparticles in SFNM is revealed. In a reducing atmosphere, SFNM shows in situ exsolution of Fe-Ni alloy nanoparticles, and then the Fe-Ni alloy is reoxidized into SFNM while converting into an oxidizing atmosphere. The polarization resistances of SFNM electrode are 0.043 Ω cm in 20% O-N and 0.064 Ω cm in H at 850 °C. Moreover, symmetric fuel cells using the SFNM electrode achieves a maximum power density of 0.501 W cm at 850 °C in H fuel, while the symmetric electrolysis cell has an electrolysis current density of 0.794 A cm at 1.29 V in 90% HO-10% H at 850 °C. It is the first time we demonstrate that the cell voltage of symmetrical cell at 0.5 A cm in the fuel cell mode and -0.5 A cm in the electrolysis cell mode can be fully recovered in 10 electrode alternating cycles and therefore demonstrate the possibility that SFNM can be used in a fully symmetric RSOC stack with electrode alternating functions.