Chemical Stability of BaMg_0.33Nb_0.67-XFe_xO_3-δ in High Temperature Methane Conversion Environments

Doped perovskite metal oxide catalysts of the form AB x C 1-x O 3-δ are of interest to the catalysis community due to the ability to fine tune the catalytic activity or chemical stability through doping. Doped barium niobate perovskites have shown remarkable stability in CO 2 sensing and methane conversion measurements. However, the reason for the chemical stability is not well understood. Doping with transition metal cations for B site cations can lead to exsolution under reducing conditions. Many perovskites used for the oxidative coupling of methane (OCM) or the electrochemical oxidative coupling of methane (E-OCM) either lack long term stability, or catalytic activity within these highly reducing methane environments. Here, we present our results obtained with a highly stable Mg and Fe co-doped barium niobate perovskite BaMg 0.33 Nb 0.67-x Fe x O 3-δ (BMNF) that has shown activity in E-OCM setups over long term (>100 hour) experiments and stability in CO 2 environments as a sensor.[1] The crystalline structure and atomic distributions within these synthesized materials analyzed via X-ray powder diffraction (XRD), scanning transmission microscopy (STEM), and X-ray photoelectron spectroscopy (XPS). Along with this, temperature programmed reaction (TPR) under 95% methane and 5% oxygen showed the effectiveness of the catalyst in an OCM setup, as well as the stability of the BMNF perovskite in methane. Through these analyses we posit that iron doping may increase the ionic conductivity of the BMNF material while change in Nb4+/5+ oxidation states prove stability in reducing environments.[2] (1) Denoyer, L. H.; Benavidez, A.; Garzon, F. H.; Ramaiyan, K. P. Highly Stable Doped Barium Niobate Based Electrocatalysts for Effective Electrochemical Coupling of Methane to Ethylene. Adv. Mater. Interfaces 2022 , 9 (27), 2200796. https://doi.org/10.1002/admi.202200796. (2) Denoyer, L. H.; Benavidez, A.; Garzon, F. H.; Ramaiyan, K. P. Chemical Stability of BaMg0.33Nb0.67-XFexO3-δ in High Temperature Methane Conversion Environments. under communication - ECS Journal of Solid State Science and Technology .