Biomimetic hydrophilic foam with micro/nano-scale porous hydrophobic surface for highly efficient solar-driven vapor generation

Solar-driven vapor generation by localized solar heating of a photothermal material is an environmentally friendly approach for seawater desalination and wastewater purification.In this work,inspired by the leaf transpiration in nature,we designed a novel bionic leaf to realize highly efficient solar vapor generation.The leaf-inspired three-dimensional(3D)material structure had a hydrophilic polyvinyl alcohol(PVA)foam layer(equivalence to the mesophyll tissue layer in a leaf)with high porosity and low thermal conductivity,a photothermal polypyrrole(PPy)layer(equivalence to the chlorophyll layer in a leaf)coated on the PVA foam,and a micro/nano-scale porous hydrophobic surface layer(equivalence to the stomal layer in a leaf).The PVA network had microchannels for water transportation and reducing water evaporation enthalpy,the PPy layer absorbed and converted solar energy to heat water locally,and the hydrophobic porous surface layer enhanced the rate of vapor escape.The asfabricated vapor generator based on the bionic-leaf structure achieved an impressive high evaporation rate of 3.09 kg m^(−2) h^(−1) under one sun irradiation(1 kW m^(−2)).The prototype vapor generator desalinated and purified brine and seawater successfully under natural sunlight.Such solar vapor generator based on the biomimetic structure provides a potential low-cost and highly efficient water purification technology to help mitigate the global water crisis using sustainable energy.