Highly efficient and stable solar-driven seawater desalination using composite photothermal structures with energy storage

Solar-driven interfacial evaporation has shown great potential in addressing the freshwater scarcity issue. Nevertheless, its performance was greatly reduced in intermittent sunlight and uncontrollable weather. Herein, we proposed a composite photothermal structure with energy storage (CPSES) to achieve efficient water evaporation, energy storage/release, and effective thermal management for continuous seawater desalination in the intermittent sunlight. It consisted of inner multi-scale pyramidal photothermal structures with microscale gradient porous copper foams, CuS nanowires and reduced graphene oxide (rGO) composite materials, and outer photothermal energy storage structures (PESS) of CuS-rGO/CF@ Paraffin. Thanks to the excellent photothermal conversion performance of the CuS-rGO photothermal structure, gradient heating effect and energy storage of PESS, the CPSES showed an evaporation rate of 4.06 kg/m²h under 1 sun illumination, which enhanced evaporation performance by 77 % compared to the composite photothermal structure without energy storage (CPS). Moreover, the CPSES showed a large evaporation rate of 3.1 kg/m²h under intermittent solar irradiation. The CPSES induced an average daily water production of 21.6 kg/m² in an outdoor sunny day, which can meet the water demand of more than 108 adults. This study provides a new approach to develop highly efficient and stable solar desalination systems in intermittent sunlight and uncontrollable weather.