Fast-Crosslinking Enabled Self-Roughed Polydimethylsiloxane Transparent Superhydrophobic Coating and Its Application in Anti-Liquid-Interference Electrothermal Device.

Polydimethylsiloxane (PDMS)-based transparent and superhydrophobic coatings have important applications, such as anti-icing, corrosion resistance, self-cleaning, etc. However, their applications are limited by the inevitable introduction of nanoparticles/high-temperature/segmented PDMS to facilitate a raspy surface. In this study, a self-roughed, neat PDMS superhydrophobic coating with high transparency is developed via a one-step spray-coating technique. PDMS suspensions with various droplet sizes are synthesized and used as building blocks for raspy surface formation by controlled curing on the warm substrate. The optimal coating exhibits a large water contact angle of 155.4° and transparency (T550 = 82.3%). Meanwhile, the employed spray-coating technique is applicable to modify a plethora of substrates. For proof-of-concept demonstrations, the use of the PDMS hydrophobic coating for anti-liquid-interference electrothermal devices and further transparent observation window for long-term operation in a sub-zero environment is shown successful. The proposed facile synthesis method of hydrophobic PDMS coating is expected to have great potential for a broad range of applications in the large-scale fabrication of fluorine-free, eco-friendly superhydrophobic surfaces.

Thin lamellar films with enhanced mechanical properties for durable radiative cooling.

Passive daytime radiative cooling is a promising path to tackle energy, environment and security issues originated from global warming. However, the contradiction between desired high solar reflectivity and necessary applicable performance is a major limitation at this stage. Herein, we demonstrate a "Solvent exchange-Reprotonation" processing strategy to fabricate a lamellar structure integrating aramid nanofibers with core-shell TiO2-coated Mica microplatelets for enhanced strength and durability without compromising optical performance. Such approach enables a slow but complete two-step protonation transition and the formation of three-dimensional dendritic networks with strong fibrillar joints, where overloaded scatterers are stably grasped and anchored in alignment, thereby resulting in a high strength of ~112 MPa as well as excellent environmental durability including ultraviolet aging, high temperature, scratches, etc. Notably, the strong backward scattering excited by multiple core-shell and shell-air interfaces guarantees a balanced reflectivity (~92%) and thickness (~25 µm), which is further revealed by outdoor tests where attainable subambient temperature drops are ~3.35 °C for daytime and ~6.11 °C for nighttime. Consequently, both the cooling capacity and comprehensive outdoor-services performance, greatly push radiative cooling towards real-world applications.

Gradient heating induced better balance among water transportation, salt resistance and heat supply in a high performance multi-functional solar-thermal desalination device.

Solar-driven desalination (SDD) is a promising technology for addressing water scarcity. However, how to overcome the trade-off between water transportation and heat supply of the evaporator to achieve a high evaporation rate and good salt tolerance simultaneously remains a challenge. Here, a novel all-in-one multi-functional SDD evaporator undergoing gradient heating is used. This evaporator incorporates a hydrophilic PDA (polydopamine)@CNT(carbon nanotube)/PVA (polyvinyl alcohol) aerogel with vertically aligned structures as the water evaporation layer, enabling rapid water transportation. Surrounding the evaporation layer, there is a photothermal hydrophobic CCP (cotton/CNT/polydimethylsiloxane) film that serves as the heating layer, enhancing the heat supply to the evaporation layer. This innovative design strikes a favorable balance between water transportation and heat supply, facilitating high evaporation rates and good salt tolerance simultaneously, while also maximizing electricity generation. Due to the wettability difference between the evaporation layer (PVA aerogel) and heating layer (CCP film), a record stable temperature gradient of nearly 70 °C was formed between the CCP film and the PVA aerogel under 1 sun irradiation, so that heat on the high-temperature CCP film was continuously transferred to the low-temperature aerogel through its thermal conductive network, leading to a high evaporation rate of 6.96 kg m-2 h-1 under 1 sun irradiation in 5.0 wt% sodium chloride (NaCl) brine (higher than the world average seawater salinity (3.5 wt%)). Meanwhile, high flux directional flow of brine generated 130 mV stable voltage and 120 µA circuit current. Furthermore, the evaporator illustrates good stability for consecutive 7 days of testing and shows industry-leading comprehensive performance of SDD in actual use. More importantly, it was tested in real Bohai seawater under weak natural light, and fresh water generated can meet the recommended daily intake of water for 2.6 households and the simultaneously generated voltage reaches above 60 mV. In addition, the evaporator exhibits good adsorption capacity for heavy metals and dye molecules. This simple and universal solar evaporation structure is suitable for the assembly of gradient thermal structures for most solar thermal materials reported in the literature, which provides a new route for maximizing the use of solar energy for freshwater and electricity generation.