A novel application of waste poplar sawdust biochar: preparation of a shape-stable composite phase-change material with excellent thermal energy-storage performance

The practical application of phase-change materials (PCMs) is limited due to leakage and low thermal conductivity. In this study, waste poplar sawdust (PW) and its derived biochar (PWC) were used as encapsulation materials, with stearic acid (SA) as the phase-change material, to successfully prepare composite phase-change materials with no leakage and high thermal conductivity. The microstructure and pore structure of PW and PWC were studied through SEM and nitrogen adsorption–desorption curves. The analysis results of FTIR, XRD and TGA indicated SA/PW and SA/PWC had excellent chemical compatibility and thermal stability. Excitingly, compared to SA/PW, SA/PWC exhibited higher latent heat and thermal conductivity. DSC results showed that the phase-change latent heat of SA/PWC can reach 100 J/g, which was 21% higher than that of SA/PW and the thermal conductivity increased by 87% times compared to SA/PW . In addition, SA/PW and SA/PWC still exhibited good thermal energy storage capacity after 200 thermal cycles. This research not only effectively resolved the leakage and low thermal conductivity challenges associated with PCMs but also introduced a novel utilization strategy for waste poplar sawdust, thereby significantly expanding its application potential.