Seawater desalination and autogenous salinity gradient for full-day electricity generation via an electrochemical system fabricated by all biomass-based materials.

Salinity gradient energy, which exists widely between two solutions with different concentrations, represents a substantial and renewable energy resource. Currently, harvesting the salinity gradient energy is largely confined to river estuaries, which significantly limits its applicability for island communities. To address this challenge, a three-compartment device that couples freshwater production with full-day electricity generation is developed, utilizing a carbonized biomass evaporator and electric double layer capacitive mixing technology. In the device, a Rattan-based solar-driven interfacial evaporator continuously concentrates the seawater during solar-driven interfacial evaporation, establishing a sustained salinity gradient between the generated high-concentration brine and the original seawater. Concurrently, the salinity gradient energy is converted into electricity by the biomass-derived ion bridges and electrodes. The system can achieve a maximum peak power density of 19.47 mW m-2 under a 10-fold concentration salinity gradient and 4.79 W m-2 under a 1000-fold salinity gradient.