Determination of Thermodynamic Parameters for the Reaction between Perovskite-type BaFe1–xInxO3−δ and CO2 Using Thermogravimetry

The standard reaction enthalpy ΔrH° and standard reaction entropy ΔrS° of the reaction between cubic perovskite-type BaFe1–xInxO3−δ and CO2 were determined by thermogravimetry at various values of the CO2 partial pressure (p(CO2)) below 1 bar, and then, the standard molar enthalpy of formation ΔfH° of the solid solution was calculated using the obtained thermodynamic parameters. The relationship between the temperature at which CO2 release occurred when the temperature increased and the given p(CO2) was obtained, which indicated the direction of the CO2 absorption or release under arbitrary conditions. Our results effectively explained the change in the CO2 release temperature at a p(CO2) of even 1 bar. A linear change in ΔfH° indicated that cubic perovskite-type BaFe1–xInxO3−δ was an ideal solid solution, consistent with the change in molar volume. Therefore, we conclude that the demonstrated thermogravimetry measurement is a suitable technique to determine the thermodynamic parameters of CO2 absorbents even in solid solutions.