3D Ordered Macroporous Mn, Zr-Doped CaCO₃ Nanomaterials for Stable Thermochemical Energy Storage

Developing high-performance Ca-based materials that can work for long-term heat transfer and storage in concentrated solar power plants is crucial to achieve the large-scale conversion of solar photon fluxes to dispatchable electricity. This work demonstrates that a series of Mn, Zr co-doped CaCO₃ nanomaterials with the 3D ordered macroporous (3DOM) skeletons are successfully prepared by a novel strategy of templated metal salt co-precipitation. The characterization results indicate that a majority of Zr and Mn are atomically dispersed into the highly-crystallized CaCO₃ framework, whereas a minor amount of Mn is present in the form of CaMnO₃ nanoparticles (NPs). The optimal 3DOM material made by templating with PS microspheres with a diameter of ≈350 nm, 3DOM-Ca80Mn10Zr10, shows a solar light absorptance of ≈74.1% and an initial energy storage density of 1706.4 kJ kg^-1. Importantly, it gives an impressive energy storage density loss of < 6.0% and maintains above 1600 kJ kg^-1 after 125 cycles. The density functional theory calculations reveal that the co-doping of Mn and Zr into the CaO crystal lattice offers a strong affinity to [Ca₄O₄] clusters, as a result, the anti-sintering of CaO NPs is significantly enhanced under high temperature.