A Highly Efficient Bifunctional Electrode Fashioned with In Situ Exsolved NiFe Alloys for Reversible Solid Oxide Cells

We developed a bifunctional electrode of Pr0.8Sr1.2(Fe,Ni)(0.8)Nb0.2O4-delta (R.P.PSFNNb) fashioned with in situ exsolved Ni-Fe alloy nanoparticles (NPs) for electrochemical oxidations of H-2, CO, and syngas as well as CO2 electrolysis. The NiFe-R.P.PSFNNb was prepared by in situ phase transition of Pr0.4Sr0.6Fe0.8Ni0.1Nb0.1O3-delta (PSFNNb) along with exsolution of Ni-Fe alloys in a reducing atmosphere, as confirmed by X-ray diffraction and X-ray photoelectron spectroscopy (XPS) characterization. XPS and H-2-temperature-programmed reduction analyses were also conducted to examine the behavior of the exsolution process. Transmission electron microscopy and electron energy loss spectroscopy element mapping concluded that the Ni-Fe alloy NPs were successfully exsolved and anchored on the parent oxide material. The NiFe-R.P.PSFNNb exhibited superior electrochemical performance for fuel electrode reactions of reversible solid oxide cells (RSOCs). A maximum peak power density of 829, 522, and 749 mWmiddotcm(-2) was obtained for the electrochemical oxidations of H-2, CO, and syngas, respectively, and a high current density of -1.89 Amiddotcm(-2) was produced in the electrochemical reduction of CO2 to CO at a temperature of 850 degrees C. More interestingly, no significant degradation of the electrochemical performance was observed in both operating modes, indicating that the NiFe-R.P.PSFNNb proposed in this work could be a promising candidate as a bifunctional electrode for the practical implementation of RSOCs.