CO 2 —H 2 O Capture and Cyclability on Sodium Cobaltate at Low Temperatures (30–80 °C): Experimental and Theoretical Analysis

Sodium cobaltate (NaCoO 2 ) is analyzed for the CO 2 cyclic carbonation–decarbonation process at low temperatures (30–80 °C) with relative humidity (RH) values between 0% and 80%, using water vapor as a catalytic intermediate. The presence of H 2 O clearly enhances the CO 2 capture at T  < 100 °C, compared with dry conditions, where the amount of CO 2 captured increases as a function of RH. These improvements are attributed to the formation of NaHCO 3 and Na 2 CO 3 during carbonation. In the case of NaHCO 3 , water vapor becomes a part of carbonation, favoring reactivity. After the carbonation analysis, the decarbonation process is analyzed using a N 2 flow, where results evidence that only NaHCO 3 decomposition takes place at low temperatures, producing NaOH and CO 2 . This result indicates that NaCoO 2 can be partially regenerated, suggesting a possible CO 2 cyclic carbonation. CO 2 carbonation–decarbonation tests are performed, confirming the cyclic capacity and stability. Moreover, the NaCoO 2 sample is modified by adding different transition metals (Fe, Cu, and Ni) to improve CO 2 —H 2 O sorption under similar physicochemical conditions. Results indicate that Fe‐containing samples present the best properties. Finally, the effect of CO 2 partial pressure on NaCoO 2 and Fe‐containing samples is analyzed using similar RHs.