Utilization of Block Copolymers to Understand Water Vaporization Enthalpy Reduction in Uniform Pores

Solar desalination, a technique converting solar irradiation to heat for evaporating saltwater and generating freshwater, has garnered much attention because of the evergrowing global demand for potable water. Herein, we utilize block copolymer-based porous carbon fibers with well-controlled porous structures to investigate the latent heat reduction in mesopores and micropores. The porous carbon fibers achieve high energy efficiencies and solar desalination rates up to 3.8 kg m(-2) h(-1) under 1 sun irradiation owing to the >99% light absorption across the solar spectrum and reduced vaporization enthalpy of poreconfined water. The nanoconfinement effect of pores is evaluated by measuring evaporation enthalpies and rates for morphologically tailored carbon fibers with pore sizes ranging from similar to 1 to similar to 22 nm. Our results show a continuous reduction in an enthalpic energy of up to 43% as mesopore size decreases to similar to 10.7 nm and then less reduction of only 14% with a further decrease in micropore size to <1 nm. The mesopores exhibit significantly enhanced evaporation rates compared with micropores due to the nanoscale confinement-related enthalpy reduction and water transport. This study provides insight into nanoconfinement effects with wellcontrolled pore sizes and contributes to further understanding and design of porous materials for future environmental applications.