Photo-Thermal Application of a Polydimethylsiloxane Foam Embedded with Carbon Nanoparticles for Interfacial Solar Water Evaporation

Freshwater scarcity is one of world biggest challenges and needs to be addressed urgently. The composites of polydimethylsiloxane (PDMS) and carbon-based materials have attracted intensive research interests over the past several decades owing to its stretchable, non-toxic features which can be applied in various fields such as flexible energy harvesting and storage devices. In this work, carbon nanoparticle (CNP) doped PDMS composite foams with an open-porous structure were fabricated via a facile salt-leaching technique to achieve excellent photo-thermal properties for solar desalination applications. The effect of different foam parameters on the photo-thermal performance of the CNP/PDMS foams was investigated and demonstrated in this thesis. The results showed that the addition of a small amount of the CNP dopants significantly improved the light absorptivity of the PDMS foams to about 97 % over the broad solar spectrum while causing little impact on the inherent low thermal conductivity of the foams. A modification using polyvinyl alcohol endowed improved surface wettability of the composite foams to provide continuous water supply to the evaporative layer. An enhanced water evaporation rate of 1.26 kg/m2h (30.24 mm /day) with an overall energy conversion efficiency of 81 % was achieved using a relatively low solar energy input of 850 W/m2. The findings in this work offer key insight for the development of photothermal composite films with high absorptivity, floatability and optimal porosity and thermal properties for the next generation of solar harvesting and seawater desalination technologies.