Shape-stabilized phase change materials based on polyvinyl alcohol/ graphene hybrid aerogels for efficient solar-thermal energy conversion

The application of graphene aerogel fabricated by reduction self-assembly and ice template methods is limited due to the difficulties in shape control and poor compression resistance. Here, a series of polyvinyl alcohol/ graphene aerogels (PGA) were prepared by the chemical crosslinking and freeze-drying method, in which (3Aminopropyl) diethoxymethylsilane (APDEMS) used as cross-linking agent and reducing agent, reduce graphene oxide (rGO) and polyvinyl alcohol (PVA) as supporting structural materials. The crosslinking effect and PVA enhancement effect achieved the shape control of aerogels and enhanced the compression resistance. When the content of graphene oxide is 50 mg, the obtained PGA5 hybrid aerogel has better compression-resilience properties with compressive strength of 6.26 KPa at 50 % compression. Then, PGA@PEG shape-stabilized phase change materials (SSPCMs) were prepared by loading PEG into PGA by vacuum impregnation. PGA5@PEG prepared with PGA5, had significant thermal conductivity of 0.481 W m-1 K-1, excellent energy storage performance (phase change enthalpy of 178.6 J/g) and good thermal cycling stability. Moreover, PGA5@PEG had high solar-thermal conversion efficiency of 86.9 %. Accordingly, we designed a solar-thermal water system to broaden the application of SSPCMs in the field of solar-thermal energy conversion. During the 2-h heating process, the PGA5@PEG-water system can rapidly reach a maximum temperature of 57.3 degrees C, higher than the pure water system (40.4 degrees C). PGA@PEG SSPCMs would be very promising as latent heat storage/release units for applications in solar energy storage and conversion.