Carbon-based hierarchical porous structure accelerates heterogeneous nucleation of PEG molecules for solar/electro-driven thermal energy storage

Fabricating porous carbon (PC) for phase change materials (PCM) by physical and chemical regulatory methods can improve the solar-heat conversion ability of the composite, however, it will inevitably disturb the electronic structure, which affects the crystallization behaviour of PCM and reduces the energy storage efficiency. In this study, we introduce a novel carbon-based hierarchical porous structure for encapsulating PCM. The unique hierarchical structure can efficiently capture photons and increase the optical paths of the system. Moreover, its large amount of meso- and macro- pores can realize the self-actuated loading process of PCM. More importantly, it can effectively promote the heterogeneous nucleation of PCM molecules and reduce the activation energy of nucleation. Consequently, the heat storage process of the composite can be triggered within 45 s under a light intensity of 100 mW·cm−2, and the photo-heat storage efficiency can reach to 80.6%. In addition, electric energy can also trigger the heat storage process of the composite, and its electro-heat storage efficiency can reach 88.1% by a low voltage of 3.0 V. Thus, the composite can storage and release thermal energy throughout the 24 h with little electric energy consumption. This work offers a new micro-scale structure engineering perspective on understanding carbon-based PCM design philosophy in renewable energy storage and utilization.