(521af) Tuning Oxygen Vacancies in Ni/CeO2 for CO2 Methanation

In-situ resource utilization (ISRU) is an essential concept for NASA-Mars exploratory missions, where the production of consumables from the conversion of captured carbon dioxide available at the International Space Station (ISS) is of interest. Specifically, the production of energy carriers, such as methane, can be achieved through the catalytic hydrogenation of CO₂. However, because of the limited available energy in the ISS, catalysts developed for CO₂ conversion must operate at low reaction temperatures (<573 K). Ni-supported particles on metal oxides (i.e., CeO₂) have been shown to result in the formation of metal-oxide interfaces with active sites that facilitate CO₂ adsorption and activation towards the formation of methane at low reaction temperatures (<573K). Furthermore, tailoring metal oxides with rare-earth metals has been shown to alter the density of oxygen vacancies resulting from charge imbalances in host metal oxides, which lead to enhanced CO₂ activation sites. Here we report on the activity of Ni/CeO₂ with enhanced metal/oxide interface sites, which exhibits methane selectivity of 99% at CO₂ conversions >80%. Our combined kinetic and catalyst characterization studies (diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), X-ray diffraction (XRD), Raman spectroscopy, and hydrogen temperature program reduction) demonstrate plausible surface intermediates and reaction pathways by which CO₂ methanation is facilitated at low reaction temperatures <573 K.