Enhanced light-to-thermal conversion performance of self-assembly carbon nanotube/graphene-interconnected phase change materials for thermal-electric device

Solar energy conversion and storage technologies have attracted more attention to alleviate the energy crisis and ecological concern. Further improvement on the thermal conductivity and photothermal storage capacity of phase change materials (PCMs) remain a huge challenge. In this work, a new composite PCMs employing carbon-based (CRGO) aerogel as the supporting material and paraffin wax (PW) as the PCM was prepared. We achieve a three-dimensional (3D) porous interconnected structure by cross-linking carbon nanotubes (CNT) with reduced graphene oxide (rGO). This 3D structure could provide more heat transfer channels and effective contact interfaces, resulting in its enhanced thermal conductivity. The aspect ratio of CNT and the ratio of CNT and rGO is regulated to optimize the 3D thermal conductive skeleton for CRGO aerogel. As a result, the multi-layer CRGO aerogel composite PCMs exhibited high solid-liquid phase change enthalpy (146.7 J/g) and excellent phase change stability. Optimal incorporation of 30 % CNT increased the thermal conductivity to 1.27 W/(m·K), which is 452 % higher than that of the pure PW. Meanwhile, a photothermal conversion efficiency of up to 90.3 % was achieved for the composite PCMs. In addition, the output voltage of the solar-thermal-electric device based on composite PCMs (150 mV) is about 3.75 times that of the blank plate (40 mV) under solar radiation. Therefore, CRGO aerogel composite PCMs show great promise for efficient solar-thermal-electric energy conversion utilization.