Hydrophobic modification of silica/exfoliated graphite nanoplatelets aerogel and its application as supporting material for form-stable phase change materials

Hydrophobic SiO2/xGnP aerogel/CA–PA form-stable phase change material with high latent heat and thermal conductivity. [Display omitted] •Hydrophobic SiO2 and SiO2/xGnP aerogels were prepared via surface modification.•SiO2/xGnP aerogels/CA–PA form-stable PCM were prepared by vacuum infiltration.•The compatibility between CA–PA and hydrophobic aerogels were improved.•The ΔH and the thermal conductivity of the form-stable PCM were greatly enhanced.•The form-stable PCM is suitable for building comfort control. Hydrophobic modified silica/exfoliated graphite nanoplatelets aerogel (M-SiO2/xGnP) were successfully prepared via surface modification of silica/xGnP alcogel and followed by ambient pressure drying. Afterwards, form-stable PCMs in which capric–palmitic acids eutectic (CA–PA) was confined in the prepared aerogels were obtained by vacuum infiltration. Characterization of the prepared form-stable PCMs revealed that both the hydrophobic modification and the doping of xGnP could effectively improve the loading of CA–PA in the aerogel. The unmodified silica aerogel could not adsorb CA–PA, while the loading of CA–PA in the surface modified pure silica aerogel supported form-stable PCM and the unmodified silica/xGnP aerogel supported form-stable PCM were 24.2wt% and 44.4wt%, respectively. Besides, the hydrophobic modification and the doping of xGnP showed significant synergistic effect. The loading of CA–PA in the M-SiO2/xGnP supported form-stable PCM (FPCM/xGnP-20-48) could attain 78.9wt% when the M-SiO2/xGnP was obtained by modifying the alcogel with 20vol% trimethyl chlorosilane for 48h. The FPCM/xGnP-20-48 not only had high latent heat and good thermal reliability, but also exhibited significantly improved thermal conductivity and alleviated supercooling due to the effective thermal conductive network formed by xGnP and the promoted heterogeneous nucleation of CA–PA at interfaces with aerogel.