In the present work alkaline promotion effects on CO2 sorption have been characterised by a series of complementary analytical techniques on alumina, magnesia, hydrotalcites and alkaline promoted corresponding materials under conditions representative for WGS conditions. Thermogravimetric analyses (TGA) and Temperature Programmed Desorption (TPD) have clearly confirmed that alkaline carbonates are destabilised when interacting with solid surface, i.e. temperature at which CO2 is released from alkaline promoted hydrotalcites is much lower than the equilibrium decomposition temperature of the corresponding bulk alkaline carbonate. In situ XRD experiments have clearly evidenced structural rearrangements in alkaline promoted hydrotalcite at the temperature used for capture. Moreover, in the presence of CO2, the reconstruction of hydrotalcite cooled at room temperature after the experiment could not be observed most probably due to the formation of new carbonate species at high temperature that are stable while temperature decreases and prevent the reconstruction of crystalline hydrotalcite. In addition, in situ vibrational spectroscopies (Raman and DRIFT) showed that carbonates rearrange while heating and that alkaline ions strongly interact with carbonate groups coordinated to aluminium oxide centres. Indeed both techniques highlight remarkably the loss of symmetry for carbonates group and comparison between parent material's fingerprints evidenced that basic (KAlnO2n/CO3)-like species play a key role in CO2 fixation at 400°C.