来源:X-MOL
Thermochemical energy storage (TCES) systems are gaining widespread consideration to increase the dispatchability of renewable energies. Reduction/oxidation of metal oxides has the advantage that air can be used during both reaction steps, simplifying the process scheme. Copper oxide is an interesting candidate, thanks to its high reaction heat and low toxicity, but it suffers from strong sintering at high temperatures because of the low melting point of Cu2O. This work investigates the use of copper/cerium mixed oxides to reduce sintering phenomena, in order to allow their use in TCES applications. Samples with different CeO2 contents were synthesized through coprecipitation and tested with a thermogravimetric analyzer in either pressure swing or temperature swing mode of operation. Material cyclability, energy storage densities, and kinetic parameters were assessed. Results showed that sintering is negligible in pressure swing but not in temperature swing, where reduction temperatures must exceed 1030 °C. Samples with higher CeO2 contents showed increased sintering resistance. In temperature swing, Cu100 melted and Cu80 showed particle agglomeration, while Cu50 only presented minor sintering effects. Volumetric energy storage densities ranged within 1000–3160 MJ m–3 depending on the sample, process conditions, and porosity considered. The kinetic analysis revealed that oxidation can be modeled as a first-order chemical reaction, whereas reduction follows a second-order Avrami–Erofeev model. Altogether, mixed Cu/Ce oxides showed interesting performance in TCES applications.