Converting waste polyimide into porous carbon nanofiber for all-weather freshwater and hydroelectricity generation

The dual system capable of solar-driven interfacial steam production and all-weather hydropower generation is emerging as a potential way to alleviate freshwater shortage and energy crisis. However, the intrinsic mechanism of hydroelectric electricity generation powered by the interaction between seawater and material structure is vague, and it remains challenging to develop dual-functional evaporators with high photothermal conversion efficiency and ionic selectivity. Herein, an all-weather dual-function evaporator based on porous carbon fiber-like (PCF) is acquired through the pyrolysis of barium-based metal-organic framework (Ba-BTEC), which is originated from waste polyimide. The PCF-based evaporator/device exhibits a high steam generation rate of 2.93 kg m -2 h -1 in seawater under 1 kW m -2 irradiation, along with the notable open-circuit voltage of 0.32 V, owing to the good light absorption ability, optimal wettability, and suitable aperture size. Moreover, molecular dynamics simulation result reveals that Na + tends to migrate rapidly within the nanoporous channels of PCF, owing to a strong affinity between oxygen-containing functional group and water molecule. This work not only proposes an eco-friendly strategy for constructing low-cost full-time freshwater-hydroelectric co-generation device, but also contributes to the understanding of evaporation-driven energy harvesting technology. An all-weather dual-functional evaporator/generator is constructed using recycled polyimide as the precursor. It not only exhibits a high evaporation rate of 2.93 kg m -2 h -1 under 1 kW m -2 irradiation, but also displays high open-circuit voltage of 0.32 V. • Porous carbon fiber is prepared by carbonizing Ba-BTEC derived from waste polyimide • PCF-based evaporator/device achieves freshwater production and energy harvesting • Evaporator shows an evaporation rate of 2.93 kg m -2 h -1 under one sun irradiation • Device continuously generates electricity with an open-circuit voltage of 320 mV • PCF evaporator delivers 7.11 kg m -2 daily freshwater yield in outdoor experiment