Graphene oxide/polyvinyl alcohol composite hydrogels with radial structure for solar steam generation

Abstract

Solar-powered interfacial evaporation is an important approach for solving the issue of freshwater scarcity. However, its practical application is often limited by slow water transport, inadequate thermal insulation, poor salt resistance, and the need for a foam to keep the evaporator afloat. Herein, inspired by the structures of tree roots, we develop a self-floating, boat-shaped aerogel with radial structures which not only achieves both fast water supply and thermal insulation, but also delivers excellent salt resistance. The design utilizes a synergistic effect between photothermal carbon fillers and surface structures to absorb a broad spectrum of sunlight, resulting in an aerogel with a solar absorption rate of 93%. The hydrophilic, radial, gradient channels facilitate fast absorption and transport of water to the evaporation surface. Meanwhile, the extremely low thermal conductivity of the aerogel reduces heat loss to the underlying bulk water. Therefore, the aerogel delivers an evaporation rate of 2.24 kgm-2h-1 under one sun with an energy efficiency of 85%. In addition, the boat shape enables prolong self-floating on simulated seawater with excellent salt resistance. This work provides an effective design towards practical application of highly efficient solar evaporators.