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CO2 Adsorption and Desorption on MgO/Al2O3: An In Situ Diffuse Reflection Infrared Fourier Transform Spectroscopy (DRIFTS) Study

The adsorption and desorption of CO2 on MgO/Al2O3 were investigated by in situ diffuse reflection infrared Fourier transform spectroscopy (DRIFTS) combined with the method of curve-fitting analysis. The spectroscopic results indicate that there are three chemisorbed surface species formed on the MgO/Al2O3, i.e., free carbonate ion, bridged carbonate, and bidentate carbonate species, which correspond to the peaks at 1675, 1403, and two peaks at 1610 and 1340 cm−1, respectively, when the sample was exposed in CO2 flow at 130 °C. The quantification analysis of the spectra during CO2 adsorption and desorption shows that the formation and desorption rates of all surface species are coverage dependent. Among the three species, the bridged carbonate shows the highest speed of formation and desorption, indicating that this type of species may be beneficial to CO2 capture and release. It should also be noted that the contribution of support Al2O3 to CO2 capture is negligible. This study may help us to understand the interaction between CO2 and metal oxides and thus to give more insights into CO2 capture using solid sorbents.