Tuning surface functionality of standard biochars and the resulting uplift capacity of loading/energy storage for organic phase change materials

Biochars have been suggested as cheap, eco-friendly, and commercially available media for adsorbing various organic and inorganic target compounds. However, there is a dearth of systematic examinations on the design of shape and thermally stable organic phase-change materials (PCMs). In this investigation, composite PCMs based on standard biochars (derived from miscanthus straw, oilseed rape, and sewage sludge feedstock via pyrolysis (at 700 °C)) and organic PCMs (1-dodecanol and n-dodecane) were developed. The as-prepared composite PCMs revealed enhanced thermal stabilities, chemical compatibilities, and moderate heat transfer performances. Among these biochar-derived composites, one from oilseed rape exhibited high heating enthalpy of 73.7 and 90.5 kJ/kg for 1-dodecanol and n-dodecane, respectively. The impregnation volume of dodecane-based composite reached 71.6%, which can be ascribed to the favorable structural (e.g., high specific surface area and high mesopore proportions) and morphological characteristics of the supporting materials. The synthesis of 1-dodecanol-based composite appeared to be influenced by specific surface areas of the biochars and intermolecular interactions owing to the highly sensitive hydroxyl group of the organic PCM. In general, this study is expected to serve as a foundation for the synthesis of “green” composite PCMs in the thermal energy storage sector.