Engineered mineral-doped biochar-infused paraffin for synergistic enthalpy storage and enhanced thermal management

Abstract The design of phase-change renewable energy-harvesting materials has garnered increasing attention for achieving sustainable energy infrastructure and advanced applications. However, energy storage density that relies on the shape and crystallization of pristine phase-change materials (PCMs) usually lacks charge/discharge efficiency, and the inherent lattice defects in individual supporting scaffolds, further constrain their overall performance. In this study, lignocellulose-based biochar (obtained from spruce thermolysis at 600 °C) was assembled with an organically intercalated montmorillonite (MT) via modification and ultrasonication-assisted vacuum drying to produce engineered biomineral-based composite PCMs that simultaneously improve the latent heat and crystallinity of paraffin PCM. The biomineral hybrid was prepared using two preparation techniques: a conventional method of integrating biochar with clay mineral without intercalation, and a structural engineering approach involving the doping of cationic nanoclay into biochar. The engineered hybrid (EMB) achieved a 516.4% increase in surface area (9.9 m 2 g –1 for bulk MT) and demonstrated a high PCM adsorption rate for hexadecane (C 16 ) with 223.3% enhancement in latent heat (15.7 to 121.3 J g –1 ). The composite (EMB@C 16 ) also exhibited a 78% enhancement of thermal conductivity and charging/discharging efficiency. Moreover, EMB@C 16 retained over 95.9% of latent heat after 1000 cycles of heating (50 °C) and cooling (23 °C), with only a 4.1% reduction, providing continuous thermal energy supply during real-time temperature variation evaluations with thermal infrared imaging under both short and long cycle durations. This fabrication technique provides a rational approach for integrating naturally sourced and thermophysically reinforced biochar-based hybrids for advanced thermal regulation systems. Graphical Abstract