Thermochemical energy storage performance and durability enhancement of Mg(OH)2/MgO composites by in-situ casting MgO particles in nanoporous carbon

Mg(OH) 2 /MgO-based thermochemical energy storage (TCES) has garnered significant interest for its potential in moderate-temperature long-term thermal energy storage, which is crucial for the stable and efficient utilization of solar energy, due to its high energy storage density, low cost, and non-toxicity. However, its practical applications are limited by agglomeration and sintering issues, which decrease the dehydration/hydration rate and reduce durability. This study focuses on designing a MgO-based composite structure by in-situ casting MgO nanoparticles within the pores of nanoporous carbon (NC). The composites were synthesized by a calcination method. Their TCES performances were tested using a thermogravimetric analysis. The NC, with an average pore size of 14.1 nm, effectively confined the growth of MgO particles within its pores, thereby producing MgO particles with small size and uniform dispersion while maintaining a high proportion of MgO in the composite. Consequently, the composite demonstrated the fastest hydration, achieving a 98.7 % conversion ratio, which was 58.9 % higher than that of pure MgO. Meanwhile, the composite exhibited a high dehydration rate and a large heat storage density of 946.5 kJ/kg. Importantly, the composite showed excellent structural stability and exhibited good durability over 60 cycles, with a slight decrease (6.0 %) in heat storage density, whereas pure MgO showed a decrease of 63.1 %. The high energy storage density and superior durability of the developed composite, compared to existing Mg(OH) 2 /MgO-based materials, make it a promising candidate for TCES applications. This study offers a reference for the rational design of TCES materials with agglomeration inhibition and reaction activity.