Nian Li

Abstract Layered titanates (Na 2 Ti 3 O 7 ·nH 2 O) with exchangeable sodium cations located in the interlayer have been synthesized by simple hydrothermal treatment of Ti precursor in concentrated NaOH solutions. By proper control of the synthesis conditions, different morphologies of nanofibers and nanosheets are obtained. The metastable layered structure of the titanates collapses during the ion exchange, resulting in irreversible ion exchange. Target cations (eg., Ag + , Cu 2+ , Pb 2+ and Eu 3+ ) are completely concentrated from water and then tightly immobilized in the interlayer which is of great significance for the removal and subsequent safe disposal of hazardous metal cations. The ion exchange of the nanosheets is much more efficient than that of the nanofibers and other inorganic ion exchangers due to the larger surface area, less stable layered structure and larger amount of interlayer water of the nanosheets. The ion exchange of the titanates is also very selective. Valence, hardness, and radius of cations are main factors affecting the selectivity. Cations trapped in the interlayer are released by an acid‐induced phase transformation of the titanate nanosheets to rutile. Then the rutile can be used as a new Ti precursor to synthesize the titanate nanostructures, resulting in a full cycle of material use. The nanosheets may find applications in the decontamination and safe disposal of radioactive and heavy metal cations and also in the collection of valuable cations from water.

The current challenge in solar thermal utilization is how to effectively convert full-spectrum sunlight into directly available thermal energy for applications at high conversion efficiency. Herein, we report a novel strategy for the construction of large-area porous CuS/polyethylene (PE) hybrid membrane as a superior interfacial plasmonic photothermal material for high-efficiency solar thermal conversion to produce steam generation off seawater. The single-layer CuS/PE membrane materials have effective full-spectra sunlight absorption, excellent solar-to-heat conversion ability, low thermal conductivity, good hydrophilicity, and open micro/nanoscopic porosity for capillarity and self-floating, etc. Impressively, a single piece of porous CuS/PE membrane under one sun illumination can exhibit a superior conversion efficiency of 63.9% from sunlight to heat of seawater evaporation. Meanwhile, the plasmonic photothermal CuS/PE membrane can be recycled at least 20 times. Therefore, with the demonstrated convenient fabrication process, low cost, and high evaporation efficiency, the single-layer porous CuS/PE membrane materials offer great promise to convert sunlight into thermal energy for practical applications of steam generation.