Novel phase change materials with superior thermal conductivity and photothermal efficiency derived from preservative-treated wood biochar

Easy leakage, low thermal conductivity and poor solar absorption capacity have emerged as primary challenges for photothermal conversion application of phase change materials (PCMs). Simultaneously, the recycling of significant quantities of waste copper-based preservative-treated wood lacks adequate method. Hence, a novel three-dimensional (3D) composite PCM with excellent thermal conductivity and photothermal conversion performance was prepared by polyethylene glycol (PEG) and biochar (PWB) derived from copper-based preservative-treated wood via one-step pyrolysis. The uniform and hierarchical distribution of copper in preservative-treated wood endowed PWB a unique way of copper doping, meanwhile avoided the complicated modifications and synthetic procedure of preparing copper-doped biochar as usual. The results revealed that PWB prepared at 1000 °C (PWB1-1000) possessed greater abundance of hierarchical pores and multilayered response structures than untreated wood biochar (WB-1000). The phase change enthalpy of PWB1-1000/PEG was 103.3 J/g, the thermal conductivity reached 0.614 W/m∙K, which represented an improvement of 101.31 % than pure PEG (0.305 W/m∙K). Due to the graphitized structure and localized surface plasmon resonance (LSPR) effect of PWB1-1000/PEG, the photothermal conversion efficiency achieved 85.85 %. This study offers a sustainable solution for waste preservative-treated wood in high-performance composite PCMs, and shows significant potential in photothermal ice melting and thermal management fields.