Hierarchical CoMn-LDH based photothermal membrane with low evaporation enthalpy and narrow bandgap toward highly efficient Solar-Driven evaporation

To date, seawater desalination is a promising strategy to alleviate the lack of freshwater. Herein, we reported fabrication of the PAN@CoMn-LDH membrane (PAN = polyacrylonitrile; LDH = layered double hydroxide) by electrospinning followed by in-situ growth and template etching strategy. Profiting from the advantages of the hierarchical structure, the PAN@CoMn-LDH membrane exhibited a high evaporation rate of 3.12 kg m−2h−1 for pure water with 94.5 % solar-to-vapor conversion efficiency under 1 kW m−2 solar irradiance. Moreover, when applied for seawater, the PAN@CoMn-LDH membrane assembled with a salt resistant device showed the evaporation rate of 3.06 kg m−2h−1 without significant decrease for 8 h. Such excellent photothermal performance can be ascribed to the fact that (1) the hierarchical structure with large surface area enhanced multiple reflection and absorption for sunlight; (2) the rich –OH groups in LDHs led to a low evaporation enthalpy of 1307.1 kJ kg−1; (3) the narrow bandgap (1.79 eV) of PAN@CoMn-LDH extended the solar absorption and facilitated the conversion of solar energy into heat, which promoted photothermal performance.