[Zurück]

D. Müller, C. Knoll, W. Artner, M. Harasek, C. Gierl-Mayer, Jan Welch, A. Werner, P. Weinberger:
"Combining in-situ X-ray diffraction with thermogravimetry and differential scanning calorimetry - An investigation of Co₃O₄, MnO₂ and PbO₂ for thermochemical energy storage";
Solar Energy, 153 (2017), S. 11 - 24.

Metal oxides with multiple accessible oxidation states are considered as promising candidates for high temperature thermochemical energy storage materials. To shed light on the chemical processes involved
in redox thermochemical energy storage materials, in-situ powder diffraction was used in combination with atmospheric control to investigate the redox-reactions of Co₃O₄, MnO₂ and PbO₂ under various conditions. Thermogravimetry and differential scanning calorimetry under the same conditions provided information on heat-flows and mass-changes. In contrast to theoretical thermodynamic considerations, only Co₃O₄ and Mn₂O₃/Mn₃O₄(originating from MnO₂) were found fully reversible. In the case of PbO₂ for none of the numerous intermediate phases any kind of reversibility was observed. The effect of the O₂-concentration in the reactive atmosphere was most distinct for the Mn₂O₃ system, notably affecting the reduction/oxidation temperatures,
whereas for the Co₃O₄ system only a moderate influence of the O₂ concentration was found. Based on the stability of the intermediate phases under various atmospheres, an isothermal TCES-cycle for Co₃O₄ and Mn₂O₃ was investigated, triggering the redox-process by an abrupt change of reactive-gas atmosphere. The fast reaction rate combined with a significant down-shift of the reaction temperatures compared to an isokinetic redox reaction suggests application as a chemical heat pump, as well towards a broadened operational profile not only in combination with concentrating solar power plants, but also with e.g. recycling of industrial flue gas heat.

metal oxides, redox system, non-ambient P-XRD, isothermal redox cycle, thermochemical energy storage

http://dx.doi.org/10.1016/j.solener.2017.05.037