Mixed-dimensional clay-based superhydrophilic film with self-desalination and high photothermal conversion efficiency

Improving solar energy conversion efficiency and salt resistance is particularly important for the practical application of green and sustainable solar steam generation technology. In this work, an interfacial evaporation polypyrrole-coated film was fabricated by the mixed-dimensional clay consisting of 1D palygorskite (Pal), 2D montmorillonite (Mt) and mica, etc., that was intercalated using polyaniline (PANI) and then introduced polyvinyl pyrrolidone (PVP) as pore-forming agent and polyvinylidene fluoride (PVDF) as a base film. The prepared film could efficiently convert light energy to heat under solar irradiation with excellent properties of self-desalination and photothermal conversion efficiency as well as superhydrophilicity and low thermal conductivity. The photothermal conversion efficiency achieved up to 93.6% under the simulated sunlight of 1 kW m⁻²_. The evaporation rate in 15% NaCl brine differed very little from that in pure water, and 0.2 g of NaCl placed on the film would be eliminated in short time at room temperature, which demonstrated that the film had salt resistance and self-cleaning capability. In addition, the resulting film had low thermal conductivity (0.09994 W m⁻¹ K⁻¹) and good mechanical properties (tensile strength of 1.1 MPa) and exhibited superhydrophilicity (water contact angle ~ 0°) which could transport water molecules rapidly.