미래를 창조하는 포스텍 화학공학과
We developed a bifunctional electrode of Pr0.8Sr1.2(Fe,Ni)0.8Nb0.2O4−δ (R.P.PSFNNb) fashioned with in situ exsolved Ni-Fe alloy nanoparticles (NPs) for electrochemical oxidations of H2, 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−δ (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 H2-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 mW·cm–2 was obtained for the electrochemical oxidations of H2, CO, and syngas, respectively, and a high current density of −1.89 A·cm–2 was produced in the electrochemical reduction of CO2 to CO at a temperature of 850 °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.