Novel composite phase change material of high heat storage with photothermal and self-cleaning function

It is vital to effectively retain the high latent heat of phase change material (PCM) when it is encapsulated in package matrix. Natural Wood has been considered as a potential matrix for PCM package as its micro-pore and nano-pore structures and rich in active groups. However, the influence of the wood pore structure on the latent heat of PCM is still unclear. In this study, paraffin wax was encapsulated with delignified balsa wood, and the influence of the pore structure of delignified balsa wood on the latent heat of PCM was investigated. The obtained results showed that the melting latent heat of the wood-based phase change material (WCPCM) with delignification treatment increased from 135.7 J/g to 175.1 J/g. This was attributed to the lower effect of the spatial confinement on the cell wall with the opening of pits and the improvement of permeability, due to the increase of the number of pores that are larger than 10 nm. The pores that are smaller than 10 nm on the cell wall were closed due to hydrogen bonding, which caused the shrinking of the wood cell wall and the increase of porosity. A superhydrophobic surface with photothermal function was constructed on WCPCM by spraying polydimethylsiloxane (PDMS) and depositing candle soot (CS). The composites can be heated from room temperature to 64.9 °C within 150 s under simulated sunlight. The efficiency of the light-thermal conversion is 87.9%. PDMS acted as an intermediate bridge to increase the stability of CS coating and gave a self-cleaning ability to the photothermal conversion coating. The composites with photothermal and self-cleaning functional coat can be used outdoor for the energy conservation of buildings.