Hierarchical porous carbon nanofibers for highly efficient solar-driven water purification

Carbon materials are commonly used in the solar steam generation because they can absorb broadband light and generate heat effectively. However, conventional carbon with a smooth surface is limited by a moderate reflection of approximately 10%, causing significant reflective energy loss. Thus, we proposed a nanoscale multiple interface strategy to boost the intrinsic light absorption of carbon nanofibers (CNFs) for more efficient solar-driven water purification. The multiple interfaces were constructed by introducing hierarchical nanopores in CNFs (HPCNFs) through a facile sacrificial framework method. Owing to the high surface roughness and abundant internal air-dielectric interfaces derived from the hierarchical pores, the HPCNFs show significant improvement in broadband light (300–2500 nm) absorption up to 97.62%, which enables high solar-vapor conversion efficiency of 96.13% and evaporation rate of 1.78 kg m −2 h −1 under one sun illumination, surpassing majority of the related carbon materials. When used for solar steam desalination, the HPCNF film demonstrates high rejection of ions (< 0.05 mg L −1 salt ions) and produces freshwater from the lake at a rate of 11.18 kg m −2 per day, adequate to satisfy the daily needs of 4–5 individuals. This work provides a facile strategy for designing efficient carbon-based solar steam generation materials.