Carbonized wood loaded with carbon dots for preparation long-term shape-stabilized composite phase change materials with superior thermal energy conversion capacity

Abstract The leakage issue, low thermal conductivity and low photo-thermal conversion capacity of organic phase change material (PCMs) greatly limits their practical utilization. Herein, a novel shape-stabilized composite PCMs with enhanced thermal conductivity and superior photo-thermal conversion efficiency was fabricated by incorporating polyethylene glycol (PEG) into porous carbonized wood loaded with carbon dots (CDs). The CDs-contained supporting material was not only characterized by unique three-dimensional porous structure, but also beneficial to prevent the leakage of melted PEG during the phase change process. The underlying reason was that extra hydrogen-bonding interaction between CDs and PEG can be readily formed in addition to surface tension, capillary action. Thus, the constructed PCMs outperformed the one without CDs incorporation in terms of shape-stabilized performance. Further, the CDs-contained PCMs exhibited high thermal conductivity (0.449 W/m K), which was comparable to the PCMs using carbonized wood as single supporting material, but showing 117% higher than that of pristine PEG. More importantly, this novel supporting material fabricated by integrating carbonized wood and CDs also imparted the resultant PCMs with high photo-thermal conversion efficiency (84.4%), latent heat (112.4 J/g), thermal reliability and thermal stability, thus demonstrating great potential utilization in constructing solar water heating systems.