Salt‐Resistant Carbon Nanotubes/Polyvinyl Alcohol Hybrid Gels with Tunable Water Transport for High‐Efficiency and Long‐Term Solar Steam Generation

Abstract

Solar steam generation has emerged as a promising technology for water purification. Carbon materials are the most widely investigated photothermal conversion materials, but it remains challenging to effectively improve the efficiency of carbon‐based photothermal films cost effectively. Herein, carbon nanotubes (CNTs)/polyvinyl alcohol (PVA) hybrid gels are designed by simply freezing/thawing the mixture of CNTs and the PVA polymers, in which the CNT light absorbers are well embedded in PVA molecular meshes. Combining the super‐hydrophilic feature and the capillary effect of the PVA porous networks, the hierarchical PVA gel enables efficient water transport from internal capillary channels to molecular meshes. Moreover, PVA molecule chains wrapped on the CNT light absorbers also function as energy‐absorbing media to reduce heat loss, achieving confinement of thermal energy to the water clusters. With this advanced solar steam generation system, the converted thermal energy can be utilized in situ to drive the vaporization of water around the CNTs. The CNTs/PVA hybrid gel shows a high energy efficiency of 90.5% and water evaporation rate of 2.06 kg m−2 h−1 under 1 sun illumination. In addition to taking advantage of the inherent bimodal porous structures, the fabricated evaporator can realize fast and long‐term stable solar steam generation.