Thermophysical properties enhancement of octadecane using reduced graphene oxide and graphene oxide nanoplatelets

•The graphene nanostructures had a notable effect on the thermal properties of the OD.•RGO enhanced the heat capacity by 385% and 491% in the solid and liquid regions, respectively.•GONPs improved the total TES capacity by 243%.•EG decreased the heat capacity by 71% and 31% in the solid and liquid regions, respectively.•EG improved the thermal stability of OD by 2%. The main aim of this study is to investigate the impact of various graphite derivatives on thermophysical properties (melting enthalpy, melting point, specific heat capacity, total heat storage thermal stability, and heat capacity) of octadecane (OD) organic paraffin as a base material for the Composite Phase Change Material (CPCM) for Thermal Energy Storage (TES). Three types of graphite derivatives additives of Reduced Graphene Oxide (RGO), Graphene Oxide Nanoplatelets (GONPs), and Expanded Graphite (EG) were mixed with the base material with four weight fractions. These ratios were 0.1, 0.3, 0.5 and 0.75 wt.% for GONPs and RGO while were 5, 10, 15, and 20 wt.% for EG. The results obtained revealed that the graphite derivatives had a significant effect on the thermophysical properties of the OD particularly the specific heat capacity (Cp). It was proved that RGO, the two-dimensional (2D) sheet structure, was the champion additive to improve the thermophysical properties of the OD. RGO increased Cp by 385% and 491% in the solid and liquid regions, respectively in comparison with the pristine base material and it was found that the total thermal energy storage (TES) capacity enhanced by 274%. Moreover, GONPs (2D) improved the Cp by 377% and 385% in the solid and liquid regions, respectively. On the other hand, the EG reduced the Cp of the OD by 31% and 71% in the liquid and solid regions, respectively. [Display omitted]