High-performance freshwater-hydroelectricity co-generation by porous carbon through waste polyester-derived MOF-assisted carbonization

The integration of interfacial photothermal conversion and hydrovoltaic effect into bifunctional evaporators has emerged as a hopeful approach to address water and energy scarcities. However, developing low-cost bifunctional evaporators and elucidating the freshwater-electricity co-generation mechanism remain challenging. In this work, we prepare porous carbon from waste polyester through a metal-organic framework (MOF)-assisted carbonization strategy and subsequently fabricate a bifunctional evaporator for freshwater-hydroelectricity co-generation. The porous carbon contains rich oxygen-containing groups and shows hierarchical micro- and mesopores with a high specific surface area of 904 m2 g−1. The porous carbon-based evaporator shows broadband and high light absorption, localized thermal management, good hydrophilicity, and high flexibility. Benefiting from these merits, it achieves high-performance freshwater and hydroelectricity co-generation, with the open-circuit voltage of 250 mV, the short-circuit current of 14 μA, and the evaporation rate of 2.34 kg m−2 h−1. Hence, it is ranked among the most efficient freshwater-hydroelectricity co-generator. Additionally, the weakened hydrogen-bonding network reduces water evaporation enthalpy to 1.7 kJ g−1. Mechanistic investigations reveal that selective Na+ interaction induces differential ion migration rate to generate streaming potential, as evidenced by molecular dynamics simulations. Meanwhile, the photothermal effect enhances voltage output by promoting interfacial ion concentration gradients. During the outdoor freshwater-electricity co-generation, it shows the voltage output of 250 mV and freshwater production of 2.34 kg m−2. This work not only puts forward a new platform to fabricate advanced evaporators from low-cost waste plastics but also unravels the freshwater-electricity co-generation mechanism, offering scalable strategies to tackle freshwater and energy crises.