Manganese oxide-based thermochemical energy storage: Modulating temperatures of redox cycles by Fe-Cu co-doping

Manganese oxides are promising materials for thermochemical heat storage at high temperatures due to their low price and toxicity. However, doping with other transition metals is needed for stabilizing the oxidation kinetics, enhancing the material durability over prolonged charge-discharge cycling. As well, this system presents a high thermal hysteresis if compared with other redox couples. Namely, metal oxide reduction takes place at higher temperatures (ca. 200 degrees C) than re-oxidation of the reduced phase. Narrowing the hysteresis loop for the manganese oxide system means that heat is stored and released in a closer range of temperatures, which could boost the energy storage efficiency. In this work, it was studied the effect that co-doping of Mn oxides with Fe and Cu has on the redox temperatures of both forward and reverse reactions. Materials were prepared by a variation of Pechini method and characterized by XRD and SEM. The capacity to withstand several redox cycles was analyzed by thermogravimetric analyses. It was found that addition of certain amount of both dopants narrowed the thermal hysteresis of such redox couple, at the same time that stable reversibility was achieved. (C) 2015 Elsevier Ltd. All rights reserved.