Solar-driven sodium alginate/carbon nanotube hydrogels enable low-enthalpy evaporation for enhanced seawater...

The strategic minimization of evaporation enthalpy has emerged as a pivotal approach for enhancing solar-driven interfacial evaporation systems. While recent advancements have reduced energy requirements, persistent challenges in scalability, efficiency, and salt rejection impede practical applications. This study introduces an innovative yet facile strategy for fabricating a high-performance solar evaporator (SCE) by transforming earth-abundant sodium alginate and commercial carbon nanotubes into a functional nanocomposite via a scalable solution-based process. The system's exceptional performance originates from the synergistic interplay of three mechanisms: molecular-scale water activation through nanoconfinement, which disrupts the hydrogen-bonding network to achieve a record-low evaporation enthalpy (806.6 J⋅g^-1); localized photothermal conversion by a well-dispersed carbon nanotube network; and hierarchical thermal management. Consequently, the SCE demonstrates unparalleled metrics: a high evaporation rate (1.387 kg⋅m^-2⋅h^-1), superior energy efficiency (86.7 %), and near-complete salt rejection (99.2 %) due to continuous ion diffusion driven by concentration gradients. Mechanistic studies, including deconvoluted Raman analysis, quantitatively confirm the manipulation of water states (evidenced by an intermediate-to-free water ratio of 1.25), providing deep insights into the nanoscale heat and mass transfer processes. This work establishes a new paradigm for sustainable desalination by leveraging molecular engineering to concurrently overcome the efficiency-salt rejection trade-off, paving the way for scalable solar water purification.