High cycling stability, hydrogen-bonds strengthening Mg(NO3)2·6H2O-propionamide composite phase change materials as energy storage material for solar thermal system

A multitude of composite phase change materials (PCM) systems have been developed, resulting in significant advancements in the efficiency of solar thermal storage systems. However, there is a paucity of inorganic-organic composite PCMs systems, and the phase change mechanism remains unclear, which significantly constrains the deployment and advancement of this category of PCMs. To address this gap in the literature, this team has developed a novel organic-inorganic composite PCM system using 30 wt% Mg(NO 3 ) 2 ·6H 2 O (MNH) and 70 wt% propanamide (POA) as raw materials. The thermal physical properties of the PCMs were initially analyzed, and the results demonstrated that the PCMs exhibited favourable latent heat and thermal cycling stability. The melting point was found to be 376.2 K, with a latent heat of melting of 131.93 J·g −1 . It was observed that the melting temperature and latent heat remained essentially unaltered after 500 cycles. Subsequently, the structure of the PCMs was analyzed using X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR). Ultimately, the interaction between liquid MNH and POA was modeled using molecular dynamics, allowing for a deeper understanding of the phase transition mechanism. It is hypothesized that the hydrogen bonds (HBs) between the two substances affects the physical bond, and that HBs contribute to the PCMs having good stability and a high thermal decomposition temperature. The rational mechanism of this phenomenon is explained from many aspects, including structure, Hirshfeld surface and thermal analysis. It is anticipated that the discovery of this new PCMs will facilitate large-scale applications in solar energy storage.