Sustainable Nanoenhanced Phase‐Change Materials Based on Paraffin Wax and Hybrid Reduced Graphene Oxide‐Activated Carbon Nanoparticles

ABSTRACT Paraffin wax (PW) is a commonly used phase‐change material (PCM) for latent heat energy storage; however, its thermal conductivity is lower (0.21 W/[m·K]), making it an alternative to choose nanoenhanced PCM. In this study, activated carbon (AC) nanoflakes derived from the waste biomass (synthesized from the dead leaves of Kigelia africana ) were treated chemically with reduced graphene oxide (rGO) nanosheets to derive a hybrid nanocomposite in a 50:50 binary mixture and dispersed in PW with concentrations of 0.1 and 0.3 wt% through a probe sonication process to attain a homogeneous mixture. The synthesized hybrid composites are characterized through X‐ray diffraction and field‐emission scanning electron microscopy. The thermal characteristics of the prepared samples, thermal behavior during phase change, thermal conductivity, and thermal stability of the composite are measured using differential scanning calorimetry, a TEMPOS thermal properties analyzer, and thermogravimetric analysis (TGA), respectively. Results showed that the composite nanoadditive PW is superior to single nanoplatelets (rGO). The thermal conductivity of the PW is improved from 0.25 to 0.49 W/(m·K) with rGO–AC and 0.41 W/(m·K) with rGO using 0.3 wt%, with a relative improvement of 96% and 64%, respectively, compared with the PW. It is also found that the composite nanoparticle in PW retained more latent heat than neat PW: at 0.1 wt%, the thermal energy storage efficiency is 105.4% with rGO–AC, indicating no measurable loss of latent heat within the measurement uncertainty, compared with 92.6% with rGO. TGA showed that both additives improved the thermal stability of the wax. With 0.1 wt% rGO–AC, the onset decomposition temperature increased by and the temperature of maximum mass‐loss rate by . The improved performance of the hybrid is attributed to the AC nanoflakes anchored within the rGO sheets, which limit sheet restacking and enhance their dispersion in the wax. The results show that a low loading of a hybrid rGO–AC additive, derived in part from waste biomass, can markedly improve heat transfer in PW while retaining its heat‐storage capacity.