An eco-friendly and facile montmorillonite nanosheets aerogel based phase change materials for efficient solar-to-thermal energy conversion

In this work, a novel montmorillonite nanosheets/poly(vinyl alcohol) aerogel (MNP) supported composite phase change material (PCM) was prepared for the first time via the facile exfoliation of montmorillonite, the ecofriendly self-assembly and freeze-drying of montmorillonite nanosheets (MNs) and poly(vinyl alcohol) (PVA), and the automatic impregnation with lauric acid (LA). Subsequently, reduced graphene oxide (rGO) was employed as a functional filler to form an MN/PVA/rGO aerogel (MNPG) and an LA@MNPG composite to improve the thermal conductivity and sunlight absorbability. The phase change enthalpies of the LA@MNP and LA@MNPG composite PCMs were 189.4 and 191.2 J/g, respectively, resulting in ultrahigh encapsulation ratios of 97.6 wt% and 98.5 wt%, respectively, along with a satisfactory structural and thermal cycle stability over 2000 thermal cycles. Furthermore, the thermal conductivity of LA@MNPG reached 0.418 W/m.K, which was almost 157% that of pure LA. At the same time, the sunlight absorbability of the composite PCMs increased from 40% to 90% upon loading with a low content of rGO (5 wt%). The LA@MNP and LA@MNPG effectively absorbed sunlight and presented ultrahigh solar-to-thermal energy conversion efficiencies of 84.72% and 91.85%, respectively. This work paves the way for the development of eco-friendly and facile composite PCMs based on montmorillonite and other lamellar silicate aluminates systems. The findings also demonstrate the potential of composite PCMs for efficient solar-to-thermal energy conversion.