Thermochemical energy storage in barium carbonate enhanced by iron(III) oxide

Renewable energy requires cost effective and reliable storage to compete with fossil fuels. This study introduces a new reactive carbonate composite (RCC) where Fe₂O₃ is used to thermodynamically destabilise BaCO₃ and reduce its decomposition temperature from 1400 °C to 850 °C, which is more suitable for thermal energy storage applications. Fe₂O₃ is consumed on heating to form BaFe₁₂O₁₉, which is a stable Fe source for promoting reversible CO₂ reactions. Two reversible reaction steps were observed that corresponded to, first, the reaction between β-BaCO₃ and BaFe₁₂O₁₉, and second, between γ-BaCO₃ and BaFe₁₂O₁₉. The thermodynamic parameters were determined to be ΔH = 199 ± 6 kJ mol^-1 of CO₂, ΔS = 180 ± 6 J K^-1 mol^-1 of CO₂ and ΔH = 212 ± 6 kJ mol^-1 of CO₂, ΔS = 185 ± 7 J K^-1 mol^-1 of CO₂, respectively, for the two reactions. Due to the low-cost and high gravimetric and volumetric energy density, the RCC is demonstrated to be a promising candidate for next generation thermal energy storage.