Assessing Cr incorporation in Mn2O3/Mn3O4 redox materials for thermochemical heat storage applications

Widening the use of renewable sources requires more efficient energy storage systems to overcome the inherent intermittence of solar energy. In this respect, thermal energy storage coupled to concentrated solar power represents an inexpensive technology to achieve that goal. In particular, the use of reversible thermochemical reactions is promising due to a higher energy storage density if compared with commercial sensible heat storage on molten salts. However, some of these systems that rely on gas-solid reactions can suffer a cycle-to-cycle loss of activity due to slow kinetics and materials degradation, which is detrimental for its potential future commercialization. In this work, we have assessed the incorporation of Cr cations in the redox couple Mn2O3/Mn3O4, as a way to stabilize the multi-cyclic activity over prolonged operation at high temperatures (650-1000 degrees C). Reduction has been studied with in situ XRD and kinetic analyses, which confirm that Cr incorporation shifts the reaction towards high temperatures. Long term redox cycling tests confirm that 5% Cr incorporation helps to stabilize the redox activity of Mn2O3/Mn3O4.

Automated summary

Incorporating Cr cations in the redox couple Mn2O3/Mn3O4 can stabilize its multi-cyclic activity at high temperatures, leading to increased efficiency of energy storage systems.