Bioinspired Flexible Composite Hydrogels for Efficient Solar Steam Generation and Stable Electricity Harvest

Integrated electricity harvesting during solar steam generation is gaining attention for maximizing energy utilization. Regrettably, the power generation efficiency is often hindered by intermittent solar irradiation. Herein, we designed a flexible solar steam generation device using a hydrogel network of polydopamine nanoparticles (PDA NPs) and poly(vinyl alcohol) (PVA) on a polytetrafluoroethylene (PTFE) substrate. Leveraging the photothermal effect of PDA and water activation of PVA, the device achieved a high water evaporation rate of 2.01 kg m^-2 h^-1 under 1 sun. More importantly, the stacked PDA NPs formed narrow channels with confinement capillarity, enabling a stable potential difference and allowing continuous electricity generation even in the absence of sunlight. A single PDA@PVA@PTFE device generated an open-circuit voltage of 0.20 V with higher outputs possible by connecting multiple units benefiting from the facile machinability. This research presents a novel approach to achieve multifunctional solar desalination, providing both fresh water and stable, all-day electrical energy.