Sustainable Underwater Solar Conversion Systems with Enhanced Electrode Environmental Compatibility

The exploitation and utilization of marine renewable resources is a significant component of marine environmental protection. Hence, a sustainable underwater energy supply system is required for related underwater devices such as environmental monitoring devices. Herein, we present an algae-inspired system that harnesses intermittent ocean solar energy to drive insertion/extraction processes of sodium ions from seawater to electrode materials for sustainable day–night energy supply. For this, we develop a combination of two optimization strategies for enhancing the environmental benignity of electrodes. The strategies include a polydopamine-assisted anchor technique to modify the Prussian blue (PB) electrode to prevent cyanide leakage. Also, a modified polyacrylonitrile-carbon felt (PAN-CF) was applied as a substitute for the MnO2 electrode to eliminate the presence of Mn metal in the water environment. After two modification strategies, the polydopamine coating technique can ensure almost no leakage of PB in the seawater. No dissolution of both the modified PB and Na-intercalated PB electrodes after being immersed can be found in authentic seawater for 4 months. Furthermore, the modified PB electrode and the PAN-CF electrode still show good electrochemical performance in day–night modes. Even after being used for 50 day–night cycles, the system still performed stably. These regulation strategies provide ideas for optimizing the environmental compatibility of electrode materials for other underwater battery systems. This is modified underwater solar conversion systems also showed other merits, such as the restoration of contaminated seawater, which promises their use as integrated devices for underwater energy supply and environmental restoration.