High-Performance Freshwater-Hydroelectricity Co-Generation by Porous Carbon through Waste Polyester-Derived MOF-Assisted Carbonization
The integration of interfacial photothermal conversion and hydrovoltaic effects into bifunctional evaporators offers a promising route to simultaneously address freshwater scarcity and energy demands. However, the development of low-cost bifunctional evaporators and elucidation of the underlying co-generation mechanism remain challenging. Here, we report a porous carbon derived from waste polyester via a metal-organic framework (MOF)-assisted carbonization strategy, which is subsequently fabricated into a bifunctional evaporator for freshwater and hydroelectricity co-generation. The porous carbon exhibits a high specific surface area of 904 m² g⁻¹, hierarchical micro- and mesopores, and abundant oxygen-containing groups. The resulting evaporator demonstrates broadband light absorption, localized thermal management, good hydrophilicity, and high flexibility. Under 1 sun illumination, it achieves an open-circuit voltage of 250 mV, a short-circuit current of 14 μA, and an evaporation rate of 2.34 kg m⁻² h⁻¹, ranking among the most efficient freshwater-hydroelectricity co-generators. The weakened hydrogen-bonding network reduces the water evaporation enthalpy to 1.7 kJ g⁻¹. Mechanistic studies, including molecular dynamics simulations, reveal that selective Na⁺ interaction induces differential ion migration rates, generating a streaming potential. Additionally, the photothermal effect enhances voltage output by promoting interfacial ion concentration gradients. Outdoor tests confirm stable voltage output of 250 mV and freshwater production of 2.34 kg m⁻². This work provides a scalable platform for fabricating advanced evaporators from waste plastics and unravels the co-generation mechanism, offering a sustainable strategy to mitigate freshwater and energy crises.