Mg AND Fe CO-DOPED PEROVSKITES FOR THE ELECTROCHEMICAL OXIDATIVE COUPLING OF METHANE IN SOLID OXIDE ELECTROLYZERS

More efficient usage of shale gas reserves and natural gas resources will allow for higher olefin yields and lower greenhouse gas emissions. The oxidative coupling of methane (OCM) is a direct pathway for converting methane to ethylene at temperatures >700 °C. The OCM process is typically regulated via the choice of catalyst, reactor conditions, temperature range and gas mixing. The electrochemical oxidative coupling of methane (E-OCM) is a modification to the OCM reaction by controlling the oxygen content via externally applied potentials to an SOEC. Perovskite oxide catalysts are useful for E-OCM due to their flexible bond networks and desired properties (conductivity, selectivity, surface area) based on synthesis/doping. This work aims to illustrate the utility of the co-doped perovskite BaMg0.33Nb0.67-xFexO3-δ (BMNF, x=0.17,0.25,0.33) for E-OCM. Validation is completed by E-OCM/OCM reaction testing and a mechanism for the unique stability of these co-doped barium niobate perovskites is determined via XPS. There is a unique tendency in BMNF for lattice incorporated Fe to remain in 3+ oxidation state with resultant Nb oxidation state accommodations occurring. The crystal structure of the BMNF material as well as its chemical stability were further explored using a computational inexpensive methodology featuring the bond-valence bond-length method which can predict a variety of material properties.