Freezing-thawing-process-free prepared self-sustained hydrogel solar evaporator for clean water and electricity...

Seawater evaporation-induced water-electricity cogeneration devices show significant potential for addressing global energy and freshwater needs. While hydrogel-based solar evaporators exhibit impressive evaporation performance, they often face challenges with non-selective ion transport in seawater, resulting in a reduced current output during evaporation. To address this issue, we develop an ionic hydrogel using a cost-effective method that eliminates the need for repeated freezing-thawing cycles. The resulting evaporator effectively manages ion and water transport, enabling simultaneous solar desalination and electricity generation. By strategically incorporating synergistic conductive additives and photothermal materials, we can greatly enhance the performance of water-electricity cogeneration by improving solar-to-vapor conversion and ion transport. This approach has led to achieving a maximum evaporation rate of 3.1 kg m^-2 h^-1, an open-circuit voltage of 732 mV, and a short-circuit current of 44 μA cm^-2 under one sun irradiation, surpassing previously reported systems and devices. The electricity generation mechanism relies on the cationic groups within the hydrogel, which selectively facilitate anion diffusion for generating streaming potential and effectively mitigate cation-induced Debye screening, thereby maximizing the energy potential of seawater.