【Frontiers in HaiChuan Chemical Technology】New high-temperature composite phase change materials offer new solutions for high-temperature applications such as solar thermal power generation and industrial waste heat recovery

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Recently, a team led by Professor Feng Wei from Tianjin University developed a new type of high-temperature composite phase-change material. This material features a high heat storage density and excellent cycle stability, offering new solutions for high-temperature applications such as solar thermal power generation and industrial waste heat recovery. The relevant findings were published in the international journal Advanced Functional Materials. The first author of the paper is doctoral student Wang Linghang, while the corresponding author is Professor Feng Wei. In high-temperature applications such as metallurgy and concentrated solar power generation, traditional medium and low temperatures? ? Phase change materials struggle to meet the demand. Although high-temperature molten salts possess a relatively high thermal energy storage density and good thermal stability, their interfacial wettability with graphene aerogel is poor; the contact angle is approximately 102°. As a result, it is difficult to achieve uniform composite formation through conventional impregnation or physical penetration methods. This often leads to molten salt leakage and uneven distribution, thereby affecting the overall performance. To address this issue, the research team proposed an interface regulation strategy, introducing polyethylene glycol (PEG) as an interface regulator into the graphene oxide and ternary eutectic salt (LiF–NaCl–Li2CO3) system, thereby improving the compatibility between the two phases through its bridging effect. A homogeneous gel system was formed by stirring at 80°C, and a stable graphene aerogel–molten salt composite structure was then constructed through directional freezing with liquid nitrogen, freeze-drying, and high-temperature annealing. During the annealing process, PEG is removed, and the molten salt is effectively confined within the porous framework of graphene. Performance test results show that the initial melting enthalpy of this composite material is 531.1 J/g, and it retains approximately 93% of its heat storage capacity after 50 high-temperature thermal cycles. Under concentrated light illumination, the material can be heated to 550°C within 25 seconds, with an average absorption rate across the entire spectrum of 92.7%; under specific testing conditions, its photothermal conversion efficiency can reach up to 91.6%. It is worth noting that as the number of thermal cycling increases, the molten salt grains within the material gradually become finer and are redistributed, resulting in a more dense filling of the pores. This leads to a significant improvement in thermal conductivity, which rises from 0.38 W·m⁻¹·K⁻¹ to 0.67 W·m⁻¹·K⁻¹. At the same time, the graphene framework provides numerous heterogeneous nucleation sites, which effectively alleviates the supercooling of the molten salt and makes the phase transition process more stable and controllable.