A Water‐Electricity Co‐Generator for Solar‐Driven Steam Production and Full‐Day Electricity Output via Harvesting Autogenous Salinity Power

The ocean holds 97% of the Earth's water and receives 60‐petawatt solar radiation each year. A multiple‐effect utilization of vast ocean resources and energy still faces significant challenges. Here, we demonstrate a water‐electricity co‐generation strategy for multiple energy conversion and full‐day electricity output. The co‐generator is fabricated by mixing an entropy battery (MEB) and a multi‐channel solar evaporator. The resultant coupled system can evaporate seawater at a rate of around 1.37 kg m −2 h −1 and elevate the salinity to 4.8 mol L −1 from an initial 0.5 mol L −1 under 1 sun condition. The autogenous salinity power is concurrently converted to electricity by MEB. Uniquely, after stopping the illumination and switching the hypersaline solution to fresh seawater, it leads to an inverted salinity power for MEB to discharge and generate electricity again. Such a strategy enables the system to deliver an average power density of 2.9 W m −2 and energy density of 229.7 kJ m −2 a day, far superior to existing MEB. Moreover, it indicates that blue energy can be harvested on the sea, not limited to certain river‐sea junctures. With further optimization of electrode materials, it is promising to consume the electricity via on‐site seawater electrolysis, achieving up‐conversion of low‐grade blue energy to green hydrogen.