TY - JOUR
T1 - Impact of La doping on the thermochemical heat storage properties of CaMnO3-δ
AU - Mastronardo, Emanuela
AU - Qian, Xin
AU - Coronado, Juan M.
AU - Haile, Sossina M.
N1 - Funding Information:
This project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement N° 74616. Support of the US Department of Energy, Office of Energy Efficiency and Renewable Energy, Award DE-EE0008089.0000, is also acknowledged. This work made use of the Jerome B. Cohen X-Ray Diffraction Facility supported by the MRSEC program of the National Science Foundation (DMR-1720139) at the Materials Research Center of Northwestern University.
Publisher Copyright:
© 2021 The Author(s)
PY - 2021/8
Y1 - 2021/8
N2 - Recently, CaMnO3 has been proposed as a promising candidate for high temperature thermochemical heat storage. The material reversibly releases oxygen in response to changes in oxygen partial pressure (pO2) in the temperature range (800-1000°C) suitable for Concentrated Solar Power (CSP) plants. However, it undergoes decomposition at pO2<0.008 atm and at temperature ≥ 1100°C, limiting its value. In this study, doping with La on the A-site (10 and 30 cat%) was explored as an approach for tuning thermochemical behavior (i.e. reaction enthalpy, reaction entropy, reaction extent, reduction onset temperature, and thermal stability). The thermodynamic properties were determined from mass loss measurements at selected pO2. Both 10 and 30 cat% La stabilized the base oxide against decomposition up to 1200°C at pO2=0.008 atm, providing access to higher operating temperatures. At 10 cat% La, both the reaction enthalpy and the reaction entropy increased, whereas both decreased at the 30 cat% doping level. The chemical heat storage capacity of Ca0.9La0.1MnO3 (~265 kJ/kgABO3) was found to be comparable to that of undoped CaMnO3, which is in turn much higher than that of Ca0.7La0.3MnO3 (~97 kJ/kgABO3) and slightly lower than was previously reported for CaMn0.9Fe0.1O3 under similar conditions. The differences between the heat storage capacities of these materials can be fully understood in terms of the differences in the enthalpies and entropies of reduction. Entropy is not a metric usually considered when estimating the thermochemical storage capacity of a material, but it is an essential property because, as discussed here, the reaction extent depends monotonically on this term. Accordingly, materials with large entropy of reduction and intermediate enthalpy of reduction, where the latter metric represents a compromise between the heat per mole of reacted oxide and reaction extent, are desirable for chemical heat storage applications.
AB - Recently, CaMnO3 has been proposed as a promising candidate for high temperature thermochemical heat storage. The material reversibly releases oxygen in response to changes in oxygen partial pressure (pO2) in the temperature range (800-1000°C) suitable for Concentrated Solar Power (CSP) plants. However, it undergoes decomposition at pO2<0.008 atm and at temperature ≥ 1100°C, limiting its value. In this study, doping with La on the A-site (10 and 30 cat%) was explored as an approach for tuning thermochemical behavior (i.e. reaction enthalpy, reaction entropy, reaction extent, reduction onset temperature, and thermal stability). The thermodynamic properties were determined from mass loss measurements at selected pO2. Both 10 and 30 cat% La stabilized the base oxide against decomposition up to 1200°C at pO2=0.008 atm, providing access to higher operating temperatures. At 10 cat% La, both the reaction enthalpy and the reaction entropy increased, whereas both decreased at the 30 cat% doping level. The chemical heat storage capacity of Ca0.9La0.1MnO3 (~265 kJ/kgABO3) was found to be comparable to that of undoped CaMnO3, which is in turn much higher than that of Ca0.7La0.3MnO3 (~97 kJ/kgABO3) and slightly lower than was previously reported for CaMn0.9Fe0.1O3 under similar conditions. The differences between the heat storage capacities of these materials can be fully understood in terms of the differences in the enthalpies and entropies of reduction. Entropy is not a metric usually considered when estimating the thermochemical storage capacity of a material, but it is an essential property because, as discussed here, the reaction extent depends monotonically on this term. Accordingly, materials with large entropy of reduction and intermediate enthalpy of reduction, where the latter metric represents a compromise between the heat per mole of reacted oxide and reaction extent, are desirable for chemical heat storage applications.
KW - Calcium manganite
KW - Lanthanum doping
KW - Perovskite
KW - Thermochemical heat storage materials
KW - Thermodynamics
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U2 - 10.1016/j.est.2021.102793
DO - 10.1016/j.est.2021.102793
M3 - Article
AN - SCOPUS:85107772374
SN - 2352-152X
VL - 40
JO - Journal of Energy Storage
JF - Journal of Energy Storage
M1 - 102793
ER -