Double-insulated porous PDMS sponge for heat-localized solar evaporative seawater desalination

Abstract

Seawater desalination has a strong potential for solving global water shortage problem, and solar-based evaporative desalination technology has received increased attention. For successful solar steam generation (SSG), solar energy should be utilized in a balanced manner through heat localization. In this study, we propose a sucrose‑carbonized sugar-templating polydimethylsiloxane (PDMS) sponge sealed with ethyl vinyl acetate (EVA) foam, called as C-STP sponge. The C-STP sponge consists of a double-layered porous structure with carbonaceous material on the top surface. The C-STP sponge exhibits high SSG performance in long-term operation with anti-salt fouling ability by its self-cleaning feature. Several factors governing the C-STP sponge were optimized by examining two different kinds of sugar with different porosity levels and carbonized layer thicknesses. The porous C-STP sponge has numerous micropores caused by sugar-leaching, thereby decreasing the thermal conductivity to improve the evaporation rate. The heat localization aspects of PDMS were also investigated. The highest solar evaporation was 1.53 kg m−2 h−1 during long-term operation up to water depletion. The C-STP sponge is easy to fabricate as a solar evaporator and has much room for enhancing solar evaporation efficiency in the future. This work on dual-insulation sponge-based SSG system will provide insights for practical applications.