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

Abstract

We developed a bifunctional electrode of Pr 0.8 Sr 1.2 (Fe,Ni) 0.8 Nb 0.2 O 4−δ (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 CO 2 electrolysis. The NiFe-R.P.PSFNNb was prepared by in situ phase transition of Pr 0.4 Sr 0.6 Fe 0.8 Ni 0.1 Nb 0.1 O 3−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 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 mW•cm −2 was obtained for the electrochemical oxidations of H 2 , CO, and syngas, respectively, and a high current density of −1.89 A•cm −2 was produced in the electrochemical reduction of CO 2 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.

Clean and Sustainable Power to X to Power by Reversible Symmetrical Solid Oxide Cells with Highly Active Ferrite Perovskite Electrodes

“…The second reduction region between 500 and 870 °C can be related to the Co−Fe alloy exsolution process, corresponding to the reduction of Fe 2+ /Co 2+ to Fe 0 /Co 0 , also, along with the phase formation of oxide. 27,33 The results of H 2 -TPR are in agreement with that of XRD, SEM, and TEM. The reduction atmosphere can induce the phase transition and Co−Fe nanoparticle formation, which can both generate a large number of oxygen vacancies and provide sufficient active reaction sites for fuel oxidation or H 2 O/CO 2 reduction.…”

Comparative Study of Exsolved and Impregnated Ni Nanoparticles Supported on Nanoporous Perovskites for Low-Temperature CO Oxidation

“…Ni Ni (6) where MW Ni is the molecular weight of Ni (58.693 g•mol −1 ), ρ is the density of Ni (8.9 × 10 6 g/m 3 ), d is the mean size of Ni NPs determined by TEM-EDX mapping (5 × 10 −9 m), a Ni is the surface area of one Ni atom (6.5 × 10 −20 m 2 /atom), and Na is the Avogadro's number. These results confirm that the Ni content titrated by H 2 -TPR corresponds to the surface and the subsurface of NiO NPs, lying between the surface and the overall loadings.…”

“…Conventional preparation methods, such as incipient wetness impregnation, infiltration, or vapor deposition, generally lead to weak nanoparticle–support interaction resulting in poor thermal stability of supported transition metallic nanoparticles (NPs). The redox exsolution method, extensively investigated over the past decade, − could overcome this issue. In contrast to classical methods, where transition metal NPs are externally deposited onto the support, this innovative approach involves the emergence of NPs directly from the bulk of the support.…”

Recent advances in exsolved perovskite oxide construction: exsolution theory, modulation, challenges, and prospects

“…6 This approach has been widely used in thermal catalysis, photocatalysis, 7 fuel cells, [8][9][10] and other elds, showing excellent catalytic performance and oxygen ion transfer capability. 7,11,12 Among them, nearly 70% of the studies on the exsolution of nonnoble metals are electrochemical applications. 13 Perovskite oxides have a relatively stable crystal structure.…”