Ni-doped La 0.4 Sr 0.6 Fe 0.95 Nb 0.05 O 3-δ (LSFNb) oxide was successfully synthesized via the ceramic method. The influence of Ni doping on the structural and oxygen-transport properties of LSFNb was investigated. In situ X-ray diffraction studies showed that Ni incorporation lowered the phase-transition temperature from the rhombohedral (R 3 ¯ c) to cubic (Pm 3 ¯ m) phase to 300 °C under both air atmosphere and vacuum . The phase diagram “3-δ − log p O₂ − T” for La 0.4 Sr 0.6 Fe 0.95 Ni 0.1 Nb 0.05 O 3-δ (LSFNbNi) oxide was obtained by the quasi-equilibrium oxygen technique. The partial molar enthalpy and entropy of oxygen were determined as functions of the oxygen nonstoichiometry. The incorporation of Ni into LSFNb resulted in an increase in the partial molar entropy owing to the increased concentration of oxygen vacancies. A hollow fiber membrane based on LSFNbNi oxide with Ni-Fe decorated surfaces was investigated for use in a catalytic membrane reactor for the simultaneous oxygen separation and the partial oxidation of methane (POM) to syngas. An in situ exsolution of Ni-Fe nanoparticles on the inner membrane surface enhanced the oxygen exchange kinetics, increasing the oxygen flux by approximately 2.8-fold and reducing the effective activation energy by half. The LSFNbNi hollow fiber membrane featuring exsolved Ni-Fe nanoparticles showed high catalytic activity in both synthetic air and POM-CO 2 -splitting modes. Plane-wave density functional theory (DFT) was used to unravel the POM mechanism and model the exsolved Ni⁰ particles on the surface of the perovskite. DFT simulations showed that the oxidative elimination of H-atoms from methane on the FeO 2 -terminated perovskite surface ceased upon the formation of stable methoxy species. Therefore, the only possibility for POM to proceed is via non-oxidative H-atom elimination from methane, which occurs on the exsolved metal Ni particles on the membrane surface. • Ni-doped LSFNb oxide was successfully synthesized via the ceramic method. • Oxygen transport properties in LSFNbNi were studied by two complementary methods. • Exsolved Ni-Fe nanoparticles enhance oxygen flux in LSFNbNi hollow fiber membranes. • LSFNbNi membrane with exsolved nanoparticles shows high activity in the POM-CO 2 splitting. • DFT calculations elucidate POM mechanism on LSFNbNi surface with exsolved Ni⁰.
Shubnikova et al. (Sun,) studied this question.