Vertical orientation graphene/MXene hybrid phase change materials with anisotropic properties, high enthalpy, and photothermal conversion

Latent heat storage of phase change materials (PCMs) is expected to be a suitable method to enhance the absorption and conversion of solar energy because of their high heat storage density and excellent chemical stability. However, pure organic PCMs are limited by their low thermal conductivity, photothermal conversion, and thermal energy storage efficiency in practical applications. Herein, vertically oriented network composite PCMs are synthesized using reduced graphene oxide/MXene hybrid aerogels (rGO/MXene) as carrier materials and encapsulating stearic acid (SA) as the PCM. Because of the vertically aligned MXene and rGO hybridized backbones, the thermal conductivity of the composite reaches 1.21 W/(mK), which increases 317.24%, compared to SA. The melting enthalpy of composites reaches 168.25 J/g, which almost retains the melting enthalpy of pure SA. The addition of rGO and MXene significantly improves the photothermal conversion capability of composite PCMs (≤90.19%). Irradiating the oriented and non-oriented surfaces of the composite sample, it is found that the temperature rise is faster in the orientation direction than in the non-oriented direction, and the equilibrium temperature of the orientation direction is 4.8°C higher than that of the non-orientation direction. This new material has a high potential for use in solar energy storage applications because of its excellent performance.