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

Abstract

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 ∼1 to ∼22 nm. Our results show a continuous reduction in an enthalpic energy of up to 43% as mesopore size decreases 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.

Scalable Fabric‐Based Solar Steam Generator

“…The evaporation enthalpy of the water in the micro‐capillaries of SDP yarn is much smaller than that of bulk water as the capillary size decreases (Figure S28 and Table S2, Supporting Information), which is consistent with Thomson's equation. [ 22 ] However, much lower water content is not beneficial to high evaporation. Thus, precise control of the water content and the water state in the yarn is crucial to designing the fabric‐based SSG with optimal performance.…”

Block Copolymer Derived Porous Carbon Fiber: An Emerging Structural Functional Material

“…It is found that the ion sorption on porous carbon fibers follows pseudo-second-order kinetics, and the analysis using the Weber–Morris model confirms that ion diffusion is not a limiting step in the ion sorption and removal process . The same concept applies to treating other contaminants such as dyes, volatile organic chemicals (VOCs), heavy metals, rare earth elements, and toxins. − The unique light-absorption capability of porous carbon fibers can potentially enable solar energy for water treatment and contaminant removal . The evaporation of water molecules within the interconnected mesopores shows reduced evaporation enthalpy and likely changes the evaporation behaviors of other molecules.…”

“…123−125 The unique light-absorption capability of porous carbon fibers can potentially enable solar energy for water treatment and contaminant removal. 126 The evaporation of water molecules within the interconnected mesopores shows reduced evaporation enthalpy 126 and likely changes the evaporation behaviors of other molecules.…”

“…The same concept applies to treating other contaminants such as dyes, volatile organic chemicals (VOCs), heavy metals, rare earth elements, and toxins. − The unique light-absorption capability of porous carbon fibers can potentially enable solar energy for water treatment and contaminant removal . The evaporation of water molecules within the interconnected mesopores shows reduced evaporation enthalpy and likely changes the evaporation behaviors of other molecules.…”

Vascular Bundle for Exceptional Water Confinement, Transport, and Evaporation

“…On account of the large body of seawater, desalination is considered a promising solution. , In light of the low cost of solar irradiation, solar desalination − represents an attractive strategy, complementing reverse osmosis, vacuum-enhanced evaporation–condensation, and capacitive desalination that require expensive forms of energy (e.g., pressure or electricity) and have a high environmental impact . Recently, many materials have shown the capability of solar desalination, including plasmonic nanostructures, − polymer gels, − porous carbon fibers, graphene, , graphene oxide, , graphene/alginate hydrogel, carbon black, and carbon foams in suspension, floating, , or contactless mode. However, compared to Nature’s uncanny craftsmanship, we must deepen our understanding of water transport, confinement, and vaporization to build systems on par with or better than biological systems.…”