Mn/al/Ce ternary-doped CaO composites for ultra-stable and solar-enhanced calcium looping thermochemical energy storage: Synergistic effects and atomic-level insights

Abstract

To address the challenges of structural degradation and low solar absorptivity in calcium-based thermochemical energy storage systems under high-temperature cycling, we propose a novel Mn/Al/Ce ternary-doped CaO composite (Ca10Mn1Al1Ce1) optimized for solar-driven calcium looping applications. Through a sol-gel synthesis strategy, the co-doping strategy synergistically integrates structural stabilization mediated by Ca₂MnO₄/Ca₃Al₂O₆ frameworks, carbonation kinetics enhancement through CeO₂-induced oxygen vacancies, and Mn element doping, significantly improving the material's solar energy absorption performance. The optimized material demonstrates unprecedented cycling stability with only 5.6 % energy density decay over 200 cycles, outperforming pure CaO (73.5 % degradation after 100 cycles). Kinetic analysis reveals accelerated calcination rates enabled by Mn doping, while DFT calculations confirm an 18.3 % reduction in CaCO₃ decomposition energy barriers. Remarkably, the composite achieves a 3.9-fold enhancement in solar absorptivity through synergistic full-spectrum light harvesting. This work establishes a multifunctional doping strategy that simultaneously addresses sintering resistance, solar absorptance, and reaction kinetics, offering a promising pathway for next-generation concentrated solar power plants requiring high-temperature, long-cycle thermochemical energy storage.