Exploring the capture and catalytic properties of sodium manganates: Bifunctional ceramics for CO/CO2 chemisorption and CO oxidation

Sodium manganate-based materials (α-NaMnO 2 and Na 2 Mn 3 O 7 ) were prepared using different synthesis procedures and precursors. Obtained samples were characterized by XRD, ATR-FTIR, N 2 adsorption-desorption and SEM, while their CO x capture and catalytic properties were evaluated using thermogravimetric and mass spectrometer techniques. Overall, significant differences in CO/CO 2 chemisorption and CO oxidation processes were observed, indicating that preparation procedures strongly influence performance; co-precipitated manganate sample exhibited a maximum CO 2 uptake of 9.5 wt% at 800 °C and 100% CO conversion at 450 °C. Specifically, an optimal α-NaMnO 2 :Na 2 Mn 3 O 7 weight ratio of 0.78:0.22 was found to exhibit the best bifunctional performance. Kinetic analysis of CO 2 capture using the Avrami–Erofeev model revealed a mechanism transition dependence from surface chemisorption to bulk diffusion. Simultaneously, CO oxidation process was found to follow a Mars-van Krevelen pathway. Na 2 Mn 3 O 7 phase facilitates low-temperature activation, while the α-NaMnO 2 phase is responsible for the higher capture yield. • Sodium-manganates enable integrated CO/CO 2 chemisorption and CO oxidation. • Phase composition determines structural properties and COx reaction performance. • The α-NaMnO 2 phase exhibits direct CO chemisorption without oxygen. • Na 2 Mn 3 O 7 promotes CO oxidation at low temperatures, enhancing efficiency. • CO 2 capture follows a redox-driven mechanism via surface and bulk processes.