Flexible Graphite Nanoflake/Polydimethylsiloxane Nanocomposites with Promising Solar–Thermal Conversion Performance

Flexible polymer nanocomposites have emerged as promising photothermal materials for various solar energy applications. However, developing photothermal materials meeting low cost, excellent light absorption capability, and facile fabrication processes has remained challenging. Herein, a set of graphite nanoflake (GnF)/polydimethylsiloxane (PDMS) nanocomposites having different concentrations from 1 to 10 wt % GnF are fabricated to find the optimum amount of GnF in a GnF/PDMS nanocomposite for the maximum absorption of solar energy within the entire solar spectrum. The optical and photothermal properties of GnF/PDMS nanocomposite films were found to be optimum at 3 wt % GnF/PDMS. Specifically, the total solar absorption is 94.8 ± 0.20%, outperforming most of the previous flexible carbon-based polymer nanocomposites. As an example of the potential application of optimized GnF/PDMS nanocomposites, a floatable interfacial water evaporator was developed by dip-coating GnF/PDMS on polyurethane (PU) foam. The coated PU at 1 wt % GnF/PDMS yields an evaporation rate of 1.14 Kg/m2·h and solar–vapor conversion efficiency of 68.2% under 1 sun illumination. The advantages of stable coating of GnF/PDMS nanocomposites and their excellent photothermal effect will benefit various solar-powered applications such as desalination, purification, and steam generation.