Laser-Induced Porous Graphene on a Polyimide Membrane with a Melamine Sponge Framework (PI@MS) for Long-Term Stable Steam Generation

Recently, solar-driven interfacial evaporation has demonstrated its huge potential in mitigating the freshwater shortage crisis. However, the pollution and salt formation on evaporation surfaces seriously hinder its practical application. Herein, we developed a porous graphene membrane originating from a polyimide membrane with a melamine sponge framework (PI@MS) through laser processing for stable and efficient interfacial evaporation. With the assistance of alternating wrapping of expanded polystyrene foam (thermal insulator) and air-laid paper (water pumping channels), which ensure plentiful water supply as well as heat localization, the porous graphene membrane achieved a high evaporation rate (∼1.31 kg m–2 h–1) and photothermal conversion efficiency (∼85.4%) under 1 sun light intensity. Moreover, the salt rejection experiment demonstrated that the evaporator developed in our work possessed remarkable stability and salt-rejecting ability as it could maintain its evaporation performance for a long time (>12 h) in a highly concentrated NaCl solution (10 wt %) without any salt crystals forming on the surface nor inside the pores of the membrane

Microgroove-Structured PDA/PEI/PPy@PI-MS Photothermal Aerogel with a Multilevel Water Transport Network for Highly Salt-Rejecting Solar-Driven Interfacial Evaporation

Desalination of seawater through solar-driven interfacial evaporation is an efficient approach to solve the freshwater resource shortage problem. However, the salt formation and crystallization during interfacial evaporation limit the long-term stability of the solar evaporator. To further improve the salt-rejecting capability of the solar evaporator, we developed a porous framework photothermal microgroove-structured aerogel (PDA/PEI/PPy@PI-MS MGA, pppMGA) through a combined freeze drying, laser engraving, and chemical polymerization technique. A multilevel water transport network consisting of a three-dimensional (3D) skeleton, a microgroove-structured water channel, and a cotton core is constructed, which can effectively improve the salt-rejecting capability of the aerogel. At the same time, the combination of the 3D porous microgroove structure of the pppMGA evaporative interface and the efficient light absorption capacity of PPy effectively increases the vapor–liquid evaporation area and the light absorption rate (98%). A high evaporation rate (∼1.38 kg m–2 h–1) and high photothermal conversion efficiency (∼93.04%) can be achieved on the pppMGA evaporator under 1 sun illumination, which can operate stably in high salt concentration (20%) water for 8 h. Even under 3 sun illumination and a 20 wt % NaCl solution, the pppMGA evaporator can operate stably without salt crystallization. Such a photothermal aerogel with high salt-rejecting performance provides a new avenue for designing an interfacial evaporation system that can operate stably under high salt concentration conditions

Hierarchical Superhydrophobic Poly(vinylidene fluoride-<i>co</i>-hexafluoropropylene) Membrane with a Bead (SiO₂ Nanoparticles)-on-String (Nanofibers) Structure for All-Day Passive Radiative Cooling

Passive all-day radiative cooling has been proposed as a promising pathway to cool objects by reflecting sunlight and dissipating heat to the cold outer space through atmospheric windows without any energy consumption. However, most of the existing radiative coolers are susceptible to contamination, which may decrease the optical property and gradually degrade the outdoor radiative cooling performance. Herein, we prepared a hierarchical superhydrophobic fluorinated-SiO2/PVDF-HFP nanofiber membrane by a facile and scalable technology of electrospinning and electrostatic spraying. Due to the synergistic effects of the efficient scattering of nanofibers/micropores and the phonon polarization resonance of SiO2 nanoparticles, the membrane achieves up to 97.8% average solar reflectance and 96.6% average atmospheric window emittance. The membrane displays sub-ambient temperature drop values of 11.5 and 4.1 °C in daytime and nighttime outdoor conditions, respectively, exhibiting remarkable radiative cooling performance. Importantly, the unique bead (SiO2 nanoparticles)-on-string (nanofibers) structure forms hierarchical roughness that endows the surface with a superior self-cleaning property. In addition, the obtained membrane exhibits remarkable flexibility and mechanical stability, which are of significant importance in cooling vehicles, buildings, and large-scale equipment

Hierarchical Superhydrophobic Poly(vinylidene fluoride-<i>co</i>-hexafluoropropylene) Membrane with a Bead (SiO₂ Nanoparticles)-on-String (Nanofibers) Structure for All-Day Passive Radiative Cooling

Passive all-day radiative cooling has been proposed as a promising pathway to cool objects by reflecting sunlight and dissipating heat to the cold outer space through atmospheric windows without any energy consumption. However, most of the existing radiative coolers are susceptible to contamination, which may decrease the optical property and gradually degrade the outdoor radiative cooling performance. Herein, we prepared a hierarchical superhydrophobic fluorinated-SiO2/PVDF-HFP nanofiber membrane by a facile and scalable technology of electrospinning and electrostatic spraying. Due to the synergistic effects of the efficient scattering of nanofibers/micropores and the phonon polarization resonance of SiO2 nanoparticles, the membrane achieves up to 97.8% average solar reflectance and 96.6% average atmospheric window emittance. The membrane displays sub-ambient temperature drop values of 11.5 and 4.1 °C in daytime and nighttime outdoor conditions, respectively, exhibiting remarkable radiative cooling performance. Importantly, the unique bead (SiO2 nanoparticles)-on-string (nanofibers) structure forms hierarchical roughness that endows the surface with a superior self-cleaning property. In addition, the obtained membrane exhibits remarkable flexibility and mechanical stability, which are of significant importance in cooling vehicles, buildings, and large-scale equipment

Hierarchical Superhydrophobic Poly(vinylidene fluoride-<i>co</i>-hexafluoropropylene) Membrane with a Bead (SiO₂ Nanoparticles)-on-String (Nanofibers) Structure for All-Day Passive Radiative Cooling

Passive all-day radiative cooling has been proposed as a promising pathway to cool objects by reflecting sunlight and dissipating heat to the cold outer space through atmospheric windows without any energy consumption. However, most of the existing radiative coolers are susceptible to contamination, which may decrease the optical property and gradually degrade the outdoor radiative cooling performance. Herein, we prepared a hierarchical superhydrophobic fluorinated-SiO2/PVDF-HFP nanofiber membrane by a facile and scalable technology of electrospinning and electrostatic spraying. Due to the synergistic effects of the efficient scattering of nanofibers/micropores and the phonon polarization resonance of SiO2 nanoparticles, the membrane achieves up to 97.8% average solar reflectance and 96.6% average atmospheric window emittance. The membrane displays sub-ambient temperature drop values of 11.5 and 4.1 °C in daytime and nighttime outdoor conditions, respectively, exhibiting remarkable radiative cooling performance. Importantly, the unique bead (SiO2 nanoparticles)-on-string (nanofibers) structure forms hierarchical roughness that endows the surface with a superior self-cleaning property. In addition, the obtained membrane exhibits remarkable flexibility and mechanical stability, which are of significant importance in cooling vehicles, buildings, and large-scale equipment