Enhanced thermal energy storage of sodium nitrate by graphene nanosheets: Experimental study and mechanisms

Molten salt is considered as one of the most promising candidate materials for solar energy storage due to its consistent performance and high energy storage density . The limited thermal conductivity of molten salt, on the other hand, has become a bottleneck for efficient energy storage and heat transfer. Here, we propose a composite phase change material (PCM) to realize ultrafast thermal energy storage based on sodium nitrate (NaNO 3 ) doped graphene nanosheets (GNS). The thermal conductivity of the composite is improved by 245 % with GNS doping ratio of 3.0 wt%, which is due to better phonon vibration matching between GNS and NaNO 3 . The decrease of phase change enthalpy and melting point are explained from the perspective of mean square displacement. This paper provides a new idea for the selection criteria of the mass fraction of nano-enhancers for molten salt-based PCMs from the perspective of phonon vibration matching.